Adolescence is one of the most rapid phases of human development, associated with marked physical, neuro­developmental, psychological and social changes. The WHO defines an adolescent as a young person in the second decade of life (10–19 years)1. Adolescent obesity has become a globally prevalent health problem affecting young people from low­ income and middle­ income countries, as well as those from high­ income countries2,3. Figure 1shows the trends in obesity for children and adolescents aged 5–19 years from differ­ent regions over 40 years from 1975 to 2016 (reF.3). A widening social disparity is recognized in economi­cally advanced countries, with an increased prevalence of obesity in more socially disadvantaged adolescents compared with adolescents from higher socioeconomic groups4. Additionally, growing evidence indicates that the prevalence of severe or morbid obesity is increas­ing in this age group in several countries, including the United States and Australia5–7.

Obesity in adolescence is often complicated by psychosocial distress and can be associated with a range of other health problems; the normal neurobiological development that occurs in this age group also has a con­siderable effect1. Furthermore, the rate of spontaneous remission of obesity to a healthy weight is low; at least 90% of adolescents with obesity will have overweight or obesity in young adulthood8,9.

For all these reasons, both the prevention and the treatment of adolescent obesity are important. In this Review, we focus on obesity treatment and detail the

evidence for, and elements of, behavioural management, the use of adjunctive therapies (such as more intensive dietary therapies, pharmacotherapy and bariatric sur­gery) and the management of the metabolic complica­tions of obesity such as insulin resistance and polycystic ovaries. The opportunities and challenges presented by the management of obesity specifically in adolescents are highlighted.

Clinical assessmentA thorough clinical history and physical examination of the adolescent is essential to assess current obesity­ associated complications, the risk of future compli­cations and whether the patient has any modifiable lifestyle practices. It is beyond the scope of this Review to provide further details on clinical assessment, and readers are referred to recent reviews and clinical guide­lines for additional information10–14. Key recommenda­tions for history­ taking and physical examination are outlined in Boxes 1,2.

Factors that affect managementNeurocognitive developmentThe pace of brain development in adolescence and into young adulthood is second only to that of early child­hood15. Pruning of previous synaptic proliferation to optimize neural networks and increasing myelination of nerve fibres for rapid neural messaging are impor­tant for the development of mature and efficient neu­ral networks. The maturation of the emotional brain

Treatment of adolescent obesityKatharine S. Steinbeck1, Natalie B. Lister1,2, Megan L. Gow2 and Louise A. Baur1,3*

Abstract | The increased prevalence of adolescent obesity and associated short- term and long- term complications emphasize the need for effective treatment. In this Review , we aim to describe the evidence for, and elements of, behaviour management and adjunctive therapies and highlight the opportunities and challenges presented by obesity management in adolescence. The broad principles of treatment include management of obesity- associated complications; a developmentally appropriate approach; long- term behaviour modification (dietary change, increased physical activity , decreased sedentary behaviours and improved sleep patterns); long- term weight maintenance strategies; and consideration of the use of pharmacotherapy , more intensive dietary therapies and bariatric surgery. Bariatric surgery should be considered in those with severe obesity and be undertaken by skilled bariatric surgeons affiliated with teams experienced in the medical and psychosocial management of adolescents. Adolescent obesity management strategies are more reliant on active participation than those for childhood obesity and should recognize the emerging autonomy of the patient. The challenges in adolescent obesity relate primarily to the often competing demands of developing autonomy and not yet having attained neurocognitive maturity.

1Discipline of Child and Adolescent Health, University of Sydney, Sydney, New South Wales, Australia.2Institute of Endocrinology and Diabetes, The Children’s Hospital at Westmead, Westmead, New South Wales, Australia.3Weight Management Services, The Children’s Hospital at Westmead, Westmead, New South Wales, Australia.

*e- mail: louise.baur@health.nsw.gov.au

https://doi.org/10.1038/s41574-018-0002-8

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with its associated reward­ seeking, hyperexcitability and proneness to impulse occurs in mid­ adolescence (14–16 years). The development of the prefrontal cortex, which is responsible for planning, organiza­tion, risk versus benefit assessment and the ability to delay immediate gratification for future gain, occurs later with final maturation in the mid­20s16 and has important implications for the management of adolescent obesity.

Choices based on emotion or impulse, difficulty in consistently following through with action plans, ina­bility to comprehend future health risks, the need to be like their peers (which makes lifestyle change challeng­ing) and the need to be independent (which reduces responsiveness to adult directives and advice as a result of prefrontal cortex immaturity16) are all likely to derail attempts at lifestyle change. The concept that lifestyle change programmes for adolescents need to be formu­lated differently from those of adults now has a strong neurocognitive rationale and an emerging clinical trial evidence base17,18.

PubertyPuberty is an early adolescent event that results in dra­matic changes in body composition and has long­ term implications for health and well­ being19. Puberty might have both positive and negative effects on weight man­agement. Positives include increasing lean body mass in males and, for both sexes, if obesity management is undertaken before the height growth spurt, then the caloric deficit induced with weight maintenance in a situation where weight would naturally increase with height increase results in reduced adiposity. Negatives include increasing adiposity in females as a result of gonadal hormones and, in both sexes, the possibility that the insulin resistance that occurs during puberty (related in part to increased secretion of growth hormone) might persist after puberty is complete if there are other drivers such as obesity present20,21. These factors need to be taken into account when managing individuals with obesity.

StigmatizationWeight stigmatization is widespread and leads to psycho logical, social and physical health consequences. Discussion of the causes and effects of weight bias and stigmatization are beyond the scope of this Review, and readers are referred to recent reviews for further details22–25. Health­ care professionals have an important role in reducing the negative effects of obesity stigma­tization. The American Academy of Pediatrics recom­mends that clinical care can be improved through role modelling, using appropriate language, good clinical documentation and ensuring a safe and welcoming environment22. Elements of behavioural health screening and behaviour change counselling, as outlined in more detail in subsequent sections, can identify and address weight­ based victimization to improve outcomes.

Overview of treatment principlesEffective obesity treatment in adolescents can be defined in various ways, including a reduction in BMI or weight outcomes, improvement in obesity­ associated compli­cations, a reduction in markers of risk of future com­plications or a changed weight gain trajectory. In adult studies, effectiveness is often categorized into ‘success’ or ‘failure’; however, no standard definition of effectiveness exists26,27, and different criteria have been used between and within studies to classify weight maintenance or regain. Calculations can also include initial weight, initial weight loss, postintervention weight, postinter­vention weight change or final weight. In adolescents, dichotomizing success is even more difficult given the need to normalize measures for age and sex in adoles­cents aged <18 years (hence the frequent reporting of BMI z­ scores) and the variability in the reporting of treatment outcomes. A systematic review and meta­ regression published in 2016 reports how weight loss in children and adolescents translates to favourable car­diometabolic outcomes28 (such as blood pressure and HDL cholesterol levels), which might be more clinically meaningful than weight loss perse.

Findings from systematic reviewsThe 2017 Cochrane Review on diet, physical activity and behavioural interventions for the treatment of obe­sity in adolescents aged 12–17 years included 44 rand­omized controlled trials (RCTs) with follow­ up periods of 6–24 months17. A range of trials that mostly used multibehavioural change interventions were included in the review, with no specific programme being rec­ommended over another. A meta­ analysis of studies comparing intervention groups versus wait­ list or no­ treatment control groups showed that, at the longest follow­ up period, there was a mean reduction in BMI of −1.18 kg/m2 (95% CI −1.67 to −0.69), in BMI z­ score of −0.13 units (95% CI −0.21 to −0.05) and in body weight of −3.67 kg (95% CI −5.21 to −2.13). The effect on weight outcomes persisted in those trials with longer follow­ up periods of 18–24 months, a finding that is somewhat at variance with those from studies in adults, which show more weight regain25.

The authors of the Cochrane Review noted that, where measured, there were improvements in percentage

Key points

•Thepreferredtreatmentapproachforadolescentpatientswithobesityincludesmanagementofobesity-associatedcomplications,adevelopmentallyappropriateapproach,supportforlong-termbehaviouralchange,long-termweightmaintenancestrategiesandconsiderationofothertherapies.

•Long-termweightmaintenancetherapy,throughface-to-faceorelectronicsupport,phonecoachingorgroupprogrammes,islikelytoberequired.

•Bariatricsurgeryshouldbeconsideredinadolescentswithsevereobesity(BMI>40kg/m2,or>35kg/m2inthepresenceofcomplications),andpatientsshouldbetreatedincentresexperiencedinbariatricsurgery.

•Pharmacotherapyshouldbeusedasadjunctivetherapy,particularlyinthemaintenanceofweightloss,andforthetreatmentofobesity-associatedcomplications.

•Cliniciansshouldunderstandwheretheadolescentisinpubertydevelopment—agedoesnotequalstage—andnotsupportbeliefsthatyoungpeoplewillgrowoutofobesitywiththeonsetofpuberty.

•Cliniciansmustworkwithinthecontextsofboththenormalrapidchangesinadolescentbraindevelopmentandthepsychosocialtasksofadolescencethatarenecessaryformatureadulthood.

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body fat, waist circumference and total fat mass follow­ing behavioural change interventions17. Improvements in quality of life, although not in self­ esteem, were also noted at the longest follow­ up. However, outcomes for dietary intake and physical activity were inconsistent across the included studies. The review reported no sub­group differences in interventions with or without paren­tal involvement or by intervention type, setting (such as school, clinic or community) or mode of delivery (group versus individual). The overall quality of evidence for the primary outcomes of interest was rated as low, except for body weight, which was rated as moderate. Adverse effects were only infrequently reported and hence could not be reliably assessed.

The findings of this most recent systematic review add to the evidence base from previous reviews12,18,29,30. The 2017 Cochrane Review did not report outcomes for cardiometabolic parameters from behavioural change interventions, although they were previously reported in a 2012 systematic review18. This review showed that life­style interventions led to statistically significant improve­ments in levels of LDL cholesterol (−0.30 mmol/l, 95% CI −0.45 to −0.15), triglycerides (−0.15 mmol/l, 95% CI −0.24 to −0.07), fasting insulin (−55 pmol/l, 95% CI −71 to −39) and blood pressure (systolic −3.72 mmHg, 95% CI −4.74 to −2.69; diastolic −1.69 mmHg, 95% CI −3.15 to −0.24) up to 12 months from baseline.

Adapting the findings from such studies to ‘real­ world’ obesity clinics that might be more poorly resourced is often difficult25. For example, in comparison with clinical trials, in usual clinical practice it might not be possible to review patients as frequently and suffi­cient specialist nursing, allied health or medical exper­tise might not be available. Further, the patients in usual clinical practice might have additional comorbidities or be more socially disadvantaged than those who partic­ipate in clinical trials, raising challenges in optimizing treatment adherence. Nevertheless, the principles of management are well recognized10–14 (Box 3).

Elements of treatment of obesityBehavioural managementBehavioural strategies are routinely used to support changes in dietary intake, physical activity levels and sedentary behaviours and to facilitate long­ term main­tenance of these changes31,32. Although most RCTs of adolescent obesity management include a behav­ioural component, these details are often inadequately described in publications17,33.

A 2015 evidence update of behavioural strategies for obesity treatment in children and adolescents identified much stronger evidence (‘well­ established interventions’) in children than in adolescents for both parent­ only interventions and family­ based behavioural

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High-income English-speaking countriesNorthwestern EuropeSouthwestern EuropeCentral EuropeEastern Europe

Fig. 1 | Trends in the number of girls (left panel) and boys (right panel) aged 5–19 years with obesity , by region, from 1975 to 2016. There has been a dramatic increase in the number of children and adolescents affected by obesity over more than four decades. Middle Eastern, East Asian, high- income English- speaking and central and southern Latin American countries are especially affected. Adapted with permission from reF.3, CC- BY-4.0.

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treatments in which parents are specifically targeted to change their own behaviours and achieve weight loss31. The update included 11 studies involving both children and adolescents undergoing behavioural weight­ loss treatment with family involvement during which the parent facilitates the lifestyle changes. Nine of these studies demonstrated improvements in weight outcomes compared with the control condition. The evidence for family­ based interventions in adolescent­ only interventions was, however, far more limited

in that few studies looked specifically at adolescents. Overall, the authors rated the evidence for behavioural weight­ loss treatment with family involvement in ado­lescents as “possibly efficacious” while commenting that treatment is optimized if parents are included in the treatment programme.

Several common behaviour change techniques are used in obesity treatment31,32,34. Some commonly used techniques include goal­ setting, stimulus control (modifying or restricting environmental influences)

Box 1 | Key elements of history taking in adolescents with obesity

general history

•Considerprenatalandbirth—includinghistoryofgestationaldiabetesandbirthweight

•Currentmedications—includingglucocorticoids,someantiepileptics(forexample,sodiumvalproate)andantipsychotics(forexample,risperidoneorolanzapine)

Weight history

•Onsetofobesityanddurationofparentalandadolescentconcernsaboutthepatient'sweight

•Previousweightmanagementinterventions

•Previousandcurrentdietingbehaviours

complications history

•Psychologicaleffectsofobesity,includingbullying,poorself-esteem,anxietyanddepression

•Sleeproutine,presenceofsnoringand/orpossiblesleepapnoea(forexample,lackofrefreshmentaftersleep,daytimesomnolenceandwitnessedapnoeas)

•Exercisetolerance

•Specificsymptoms,including-Acneandhirsutism-Morningheadacheandvisualdisturbance(potentialbenignintracranialhypertension)-Gastrointestinal:vomiting,abdominalpain,constipationandgastrointestinalreflux-Nocturnalenuresisanddaytimedribbling-Hipandkneejointpain-Menstrualhistory(girls)

Family history

•Ethnicity(high-riskgroupsforcardiometaboliccomplicationsincludeNativeAmerican,Hispanic,Maori,PacificIslander,AustralianAborigine,SouthAsian,EastAsian,MediterraneanandMiddleEastern)

•Familymemberswithahistoryof-Obesity- Type2diabetesmellitusandgestationaldiabetes-Hypertension,dyslipidaemiaandcardiovasculardisease-Obstructivesleepapnoea- Polycysticovarysyndrome- Bariatricsurgery- Eatingdisorders

•Homeenvironment,including-Householdmembers- Parentalrelationship- Parentalemployment,hoursandhomesupervision

lifestyle factors

•Dietanddiet-relatedbehaviours- Breakfastconsumption- Eatingpatterns,includingsnacking,sneakingfood,fast-foodintakeandbingeeating- Beverageconsumption(sodas,juiceandothersugarydrinks)- Familyroutinesaroundfoodandeating

•Physicalactivity- Transporttoandfromschool- Sportsparticipation-After-schoolandweekendrecreation- Familyactivities

•Sedentarybehaviours- Screentimeperday(TV,videogame,cellphone,tabletandcomputeruse)-NumberofTVs,computers,tablets,laptops,cellphonesandgamingconsolesinthehouseandbedrooms- PatternofTVorotherscreenviewing(forexample,duringmeals)

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and self­ monitoring (Box 4). Note that goals need to be concrete, developmentally relevant and achievable and might take considerable time to set and review in clin­ical sessions. Reward systems support the repetition of a desired behaviour and can include rewards based on improvements in lifestyle behaviours as well as in weight outcomes. Importantly, behaviour change strategies should be used by all treating clinicians.

Further research is needed to develop a stepped model of care for treatment (especially for adolescents), to identify the optimal intensity and frequency of behav­ioural treatments for long­ term sustainability and to enhance scalability and implementation into community and clinical settings.

Dietary interventionsFollowing dietary interventions is effective for mod­est weight loss in adolescents with obesity18. Caloric restriction is usually incorporated into multicomponent lifestyle­ based interventions for weight management. Importantly, lifestyle interventions that include a dietary component can improve cardiometabolic outcomes in adolescents with obesity even in the absence of weight loss or changes in body composition18,29,33.

Various dietary manipulations can achieve caloric restriction and resultant weight loss in adolescents, most commonly by using the ‘stop/traffic light approach’ but also by altering macronutrient distributions and/or improving carbohydrate quality. No dietary intervention has been shown to be optimal, and adherence to die­tary protocols is the most effective predictor of weight loss35. Dietary interventions with evidence of being effective for weight management are discussed in the following sections.

Stop/traffic light approach. This calorie­ controlled inter­vention categorizes foods according to caloric density and uses these groups to guide intake frequency (Fig. 2). Low­ calorie foods are labelled ‘green’ and can be eaten freely, moderate­ calorie foods are labelled ‘yellow’ and should be eaten judiciously and high­ calorie foods are labelled ‘red’ and should be eaten rarely36. This approach can produce effective weight loss (BMI decreases range from 0.18 to 2.6 kg/m2)37,38 in adolescents in the short to medium term (6 months to 2 years)18.

Macronutrient distribution. Altering the macro nutrient ratio of a calorie­ restricted diet is purported to improve dietary adherence, weight­ loss outcomes and cardi­ometabolic measures39. Common diet interventions have different macronutrient distributions (Fig. 3). Conventional interventions are typically referred to as ‘low fat’ and aim for <35% daily energy from fat. A low­ carbohydrate diet, aiming for <50 g carbohydrate per day, has often been compared to a low­ fat approach; however, a 2014 systematic review found no evidence that either approach was more effective for long­ term weight loss in adolescents39. Even so, low­ carbohydrate diets might provide some benefit for short­ term weight loss (BMI decreases from baseline range from 1.2 to 5.2 kg/m2)39 and insulin concentrations (the decrease in fasting insu­lin levels from baseline range from 6.0 to 7.5 μU/l)40,41 compared with low­ fat interventions. In longer­ term studies of >12 months, weight loss was not significantly different, possibly owing to eventual migration to a more typical carbohydrate intake35,39.

Increasing protein from a typical 15% of daily energy in conventional diets to 20–40% of daily energy has no demonstrated benefit for weight loss in adolescents under isocaloric conditions39. Increasing protein intake is hypothesized to improve satiety and reduce hunger, thereby resulting in a lower ad libitum energy intake and greater weight loss42. However, studies in free­ living adolescents demonstrate that achieving higher dietary protein targets is difficult43, which might contribute to the lack of effect of increased levels of dietary protein in adolescents. The unique challenges to dietary compliance

Box 2 | notable findings on physical examination10–14

Skin or subcutaneous tissues

•Acanthosisnigricans(neck,axillae,skinfoldsandoverjoints)

•Keratosispilaris

•Acrochordons(skintags)

•Hirsutism

•Acne

•Striae

•Pseudo-gynaecomastiainmales

•Intertrigowithorwithoutsecondaryinfection

•Xanthelasmas(hypercholesterolaemia)

neurological

•Papilloedemaand/orreducedvenouspulsationsonfundoscopy(pseudotumourcerebri)

Head and neck

•Tonsillarsizeandobstructedbreathing

cardiovascular

•Hypertension

•Heartrate(cardiorespiratoryfitness)

respiratory

•Exerciseintolerance

•Wheeze(asthma)

gastrointestinal

•Hepatomegalyandhepatictenderness(nonalcoholicfattyliverdisease)

•Abdominalpain(secondarytogallstonesorgastro-oesophagealreflux)

Musculoskeletal

•Pesplanus

•Groinpainandpainfulorwaddlinggait(slippedcapitalfemoralepiphysis)

•Lowerlimbarthralgiaandrestrictionofjointmovement

Endocrine

•Goitre

•Extensivestriae,hypertension,dorsocervicalfatpador‘buffalohump’(signsofCushingsyndrome)

•Pubertalstaging

•Reducedgrowthvelocity

Psychosocial

•Flataffectandlowmood(depression)

•Poorself-esteemandsocialisolation

other — evidence of a possible underlying genetic syndrome

•Shortstatureordisproportion

•Dysmorphism

•Developmentaldelay

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during adolescence are not well defined in the literature but include peer influences, reliance on parental support (including the provision of meals) and the neurocognitive development issues outlined in a previous section.

Carbohydrate quality. Glycaemic index (GI) and gly­caemic load are used to describe carbohydrate qual­ity. Although low­ GI diets do not seem to confer any weight­ loss benefit for adolescents, a 2015 systematic review found that lower­ GI diets improved insulin resistance (HOMA index mean difference of −0.70, 95% CI −1.37 to −0.04, P = 0.04) and triglyceride concentra­tions (mean difference −15.14 mg/dl, 95% CI −26.26 to −4.00, P = 0.008)44. The major limitation with manipulat­ing GI to improve carbohydrate quality is that lower­ GI foods do not always translate to ‘healthy’ options; for example, high­ fat discretionary foods such as ice cream and potato chips have a low GI.

Intermittent fasting. Over the past decade, intermit­tent energy­ restricted diets have gained popularity as a weight­ loss approach in adults45,46. Limited evidence is available for their use in adolescents; however, these diets have been used in clinical practice. Dietary model­ling and nutrient analysis show that, over a 7­day period (3 days restricted to ~2.5–2.9 MJ or 600–700 kcal), inter­mittent energy­ restricted meal plans can be designed to meet adolescents’ unique micronutrient requirements47.

More intensive dietary therapiesA very­ low­energy diet (VLED) is an intensive die­tary regimen, typically consisting of <800 kcal per day, with <50 g of carbohydrate and adequate provision of micronutrients often being achieved using meal replace­ments such as shakes and bars. Owing to the difficulty of achieving the strict calorie prescription, this diet is typically recommended only for short periods of time (8–12 weeks)48.

In adolescents with obesity, a VLED can safely induce rapid weight loss in the short term (4–15 kg over 3–12 weeks) while preserving lean body mass49,50. VLEDs also lead to short­ term improvements in common met­abolic risk factors49,51. Published in 2016, a small pilot study demonstrated that VLED reversed type 2 diabetes mellitus (T2DM) in newly diagnosed adolescents with obesity50. However, the long­ term (>12 months after

completion of VLED) outcomes remain unclear. The severe nature of the diet requires intensive monitoring by health professionals; however, these diets could be an alternative to pharmacological therapies or surgical interventions to treat adolescents with severe obesity.

Eating behavioursAn emerging area of research is the role of eating behav­iours in obesity, defined as “self­ perceived behaviour and attitudes towards eating behaviour and food” (reF.52), which could partly explain the different responses to dietary interventions seen in patients. Longitudinal data on eating behaviours and weight gain are limited, and few intervention studies directly assess more than one eating behaviour53. In adolescents, prescriptive dietary advice consisting of hypocaloric nutrition coaching by a trained dietician can normalize eating behaviours in the short to medium term54. However, more data are needed to prospectively examine the long­ term effects of dietary interventions on the eating behaviours of adolescents.

Physical activityAdolescent obesity is associated with suboptimal physi­cal activity levels, poor fitness and excessive time in sed­entary behaviours55. Despite the certain contributions to energy deficit, the specific weight­ reducing effect of the physical activity component of a lifestyle intervention in adolescents with obesity is not clear. However, phys­ical activity is still an integral part of obesity treatment owing to the additional health benefits attained through regular exercise, including improved body composi­tion, psychological profile and functional capacities55–62 (Fig. 4). Physical activity is also associated with improve­ments in the cardiometabolic profile of an adolescent with obesity, including improved insulin sensitivity, blood pressure and cholesterol levels55–62. Hence, regu­lar physical activity has an important role in preventing the development of the metabolic syndrome and T2DM in adolescents with obesity, irrespective of a change in weight. One systematic review comparing diet­ only with diet­ plus­exercise or an exercise­ only interven­tion found that, although weight loss was not different between the groups, the addition of exercise training to a dietary intervention led to a greater improvement in levels of HDL cholesterol and fasting insulin concentra­tions in the short term (over 6 months) than a diet­ only programme29.

Several national guidelines recommend that all ado­lescents partake in at least 60 minutes of daily moderate­ to­vigorous physical activity and that no more than 2 h per day is spent using electronic media for entertainment (for example, computer games, TV and Internet)63–66. However, few adolescents achieve these targets55. This challenge is exemplified in adolescents with obesity, who often report negative peer experiences around exercise67 and have reduced exercise tolerance, which presents a barrier to participation in physical activity owing to the early onset of fatigue68. Reduced capacity to perform basic physical functioning tasks, including walking and climbing stairs, has led to obesity in adoles­cents being described as a disability69. Exercise capacity in adolescents with obesity can be enhanced through

Box 3 | Principles of obesity treatment

•Assessandmanageobesity-associateddisorders

•Ensureadevelopmentallyappropriateapproach

•Supportlong-termbehaviourchange

•Dietarychange

•Increasedphysicalactivity

•Decreasedsedentarybehaviours,includingscreenbehaviours

•Improvedsleep

•Strategiesforlong-termweightmaintenance

•Considermoreintensivedietaryinterventions

•Considerpharmacotherapy

•Considerbariatricsurgery

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participation in a 12­week exercise intervention of twice weekly 45–60 minute sessions, including resistance and aerobic exercise, supervised by a personal trainer62.

By increasing adolescents’ participation in physical activity, it is anticipated that a flow­ on effect will occur, resulting in reduced recreational screen time. However, both issues need to be addressed. A recreational screen time allowance of 2 h per day is increasingly difficult to implement given the prominence and accessibility of digital technologies. Effective interventions for reducing screen time in adolescents with obesity are still needed. Utilization of technologies, such as smartphone apps, is a popular avenue of research in this area70.

Sleep behavioursCross­ sectional studies show an association between short sleep duration and an increased risk of over­weight or obesity in children and adolescents, with a pooled odds ratio of 1.89 (95% CI 1.43–1.68) for short sleep duration (different definitions used in the vari­ous studies, including <5 h, <6 h and <10 h) and obesity being noted in a systematic review of 12 studies71. In a systematic review of 22 longitudinal studies, an inverse association was found between short sleep duration and subsequent BMI in both children and adolescents72. On the basis of adult studies73,74, interventions targeting sleep in the management of adolescents with obesity might result in improved weight and body composi­tion outcomes. Trial data in adolescents are limited, and

no trials have been conducted in young people already affected by obesity75,76. Strategies might include an earlier adolescent bedtime, removal of electronic screen devices from the bedroom and family rules about exposure to screens before bedtime. Importantly, targeting sleep has additional benefits in terms of general health, mood, school performance and quality of life77.

Digital technologiesHigh­ quality studies using digital technologies to man­age obesity are lacking78. A 2017 meta­ analysis of all mobile health interventions in youth concluded that these “appear to be a viable behaviour change interven­tion modality for youth” (reF.70). Digital technologies represent a promising area of future clinical research in adolescent obesity, including apps and activity track­ers as lifestyle monitors. Apps and activity trackers can give instant feedback on levels of physical activity, sleep and active versus sedentary time, with little input required from the user. Popular apps are also used for tracking diet or providing healthy food alternatives. Technologies including image or photo upload of foods and/or barcode scanning are designed to minimize the time required for input from the user and enable instant feedback on dietary intake or advice on more appro­priate choices. However, the capacity of such devices to assist weight loss is not yet clear, with a study published in 2016 demonstrating that adults randomly assigned to the ‘wearable device’ (activity tracker) arm achieved less weight loss at 24 months than those in the con­trol arm79. Furthermore, these technologies will never replace a clinician, but they might be a useful tool to enhance motivation and assist in weight­ loss mainte­nance, particularly in adolescents, who generally enjoy digital devices. Discoveries from research in mental health provide support for the use of the Internet to deliver interventions80. In order to be engaging and to be considered for long­ term use, such interventions (including apps) should be co­ designed with adolescents and undergo regular updates. Their commercial viability is questionable.

Long- term weight outcomesFew high­ quality trials report long­ term outcomes of obesity treatment in adolescents, as opposed to chil­dren17,18,81. However, in a large central European health­ care database from 157 paediatric specialist centres managing obesity (patients aged 5–25 years), 2­year outcomes were reviewed for 3,135 patients82. Compared with children aged 5–11 years, adolescents aged 12–15 years had a 41% lower odds of successful weight reduction and maintenance, defined as a decrease in BMI z­ score of at least 0.2 from baseline. These findings emphasize the importance of early treatment of estab­lished obesity. In a 12 month and 24 month follow­ up of adolescents participating in a trial of two different types of dietary intervention, weight loss in the first 3 months predicted long­ term weight outcomes83, a finding con­sistent with those from other studies. Such studies sug­gest that interventions with a focus on early weight loss might have better outcomes than interventions started after the patient has had obesity for some time.

Box 4 | Examples of common behavioural change techniques

goal- setting — performance goals

•“Iwilldecreasemydiscretionaryscreentimefrom6hperdayto4hoverthenextmonth.Iwilldothisbymovingmycellphoneoutofmyroomatnight(Iwillchargeitinthefamilyroom)andbyagreeingtomovemylaptoptothefamilyroom.WhenIhavedonethis,Iwillworkoutsomenewscreentimegoals.”

•“Iwillgotobedanhourearlieronschoolnights(11pminsteadofmidnight).Iwilldothisbychargingmycellphoneinthefamilyroomovernight.”

•“Iwillgetanextrahalfhourofphysicalactivityintomyday.Iwilldothisbycatchingthetrainandbustoandfromschoolinsteadofaskingmyparentstodriveme.Iwillalsoaskmyfriendtogototheschoolgymwithmetwiceaweekafterschool.”

goal- setting — outcomes goals

•Specificweight-lossgoals(amountofweightlossorreductioninwaistcircumferenceoveraspecifiedtime),developedinconsultationwiththetherapist

Self- monitoring

•Dailymonitoringandrecordingofphysicalactivityviapedometerorotheractivitymonitor

•Dailyrecordingofscreentime

•Dailyrecordingofeatinghabits(forexample,eatingbreakfastandeatinglunch)orofspecificfoodintake(forexample,vegetableintakeandsodadrinkintake)

•Weeklyrecordingofweight

Stimulus control

•Parentagreestonotoffertodrivetheyoungpersontoschool

•Television,laptops,cellphonesandothermobiledevicesareoutofthebedroomatnight

•Parentandyoungpersonagreetonotstoreunhealthyfoods(forexample,processedsnackfoodsandsodadrinks)inthehouse

•Parentagreestoserveeveningmealusingsmaller-sizedplates

•Parentagreestohaveafamilyruleabouteatingtheeveningmealatthetablewithoutthetelevisionbeingon

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In adults, a comprehensive weight maintenance pro­gramme is recommended for those who have had initial weight loss32. This programme might entail continued support from a therapist, via phone or face to face, pos­sibly on at least a monthly basis for ≥12 months. The sustainability of such an approach in usual health­ care settings and the applicability to the adolescent popula­tion remain unclear. However, given the importance of digital technologies to young people, this might prove to be of relevance in weight maintenance strategies.

PharmacotherapyIn the long term, safe anti­ obesity drugs must be a therapeutic goal given that the condition is chronic and lifestyle therapies have had limited results. Current anti­ obesity agents are universally limited in both num­ber and availability, with few subsidized by govern­ment agencies (TaBle 1). Trials are mostly performed in adults, and use in adolescents is often off­ label. A 2016 Cochrane Review provided data for trials of current (and some previously available) anti­ obesity agents in children and adolescents84. The authors also identified ongoing trials for topiramate and glucagon­ like peptide 1 receptor (GLP1R) agonists. Metformin and orlistat both result in a reduction in weight in favour of the active intervention, albeit around 2 kg. The review also describes a greater overall attrition rate for adolescents than reported in adult trials. Metformin and orlistat are available for adolescent use in most jurisdictions, although use of metformin generally remains off label in those without diabetes mellitus.

Some antidepressants have weight loss as a bene­fit but are not first­ line obesity pharmacotherapies. In some countries, bupropion is used as an antidepressant and in others it is licensed only for addiction therapies. When bupropion is combined with naltrexone as a slow­ release preparation, there is benefit compared with pla­cebo for weight loss85. The data for topiramate's effect on body weight in adults are positive but compromised by adverse effects such as dizziness and drowsiness86.

Topiramate is currently marketed for epileptic seizures and migraine and could be considered in adolescents with obesity who fulfil prescribing criteria. Topiramate has been trialled for weight loss in adults in combination with phentermine, with a significant dose­ dependent percentage change in body weight of 7–9% compared with placebo85. However, a pilot RCT in 30 adolescents consisting of 24 weeks of topiramate following 4 weeks of meal replacement therapy did not result in significant BMI reduction87.

Glucagon­ like peptide 1 (GLP1) is a naturally occur­ring incretin produced by the gut88. GLP1R agonists were originally marketed for the treatment of T2DM. An additional effect is appetite suppression and weight loss89, and obesity management has become an addi­tional indication for the use of this drug class. In adults, the effects of liraglutide, which is approved for weight loss in many countries as a once­ a­day injection, are impressive compared with the effects of standard oral anti­ obesity therapy. Published in 2017, the results of an RCT showed that the oral GLP1R agonist semaglu­tide had a statistically significant effect on weight loss of 2–7 kg as well as control of diabetes mellitus in par­ticipants with T2DM and a mean age of 57 years. This finding suggests that oral therapy is a future, adolescent­ attractive weight­ loss option90. In a pilot RCT, 3 months of exenatide therapy in 26 adolescent patients with severe obesity led to a greater percentage reduction in BMI, as well as absolute weight and BMI, than placebo91.

Bariatric surgeryIn adults, bariatric surgery is a well­ recognized form of therapy for severe obesity as an adjunct to behavioural therapy and pharmacotherapy92. The role of bariatric surgery in adolescents is being established.

Evidence for bariatric surgeryTo date, there has been only one published RCT of bar­iatric surgery in adolescents: an Australian study of 50 patients aged 14–18 years (25 patients in both the intervention and the comparator groups)93. The study compared laparoscopic adjustable gastric banding (LAGB) with a multicomponent lifestyle programme. At 2 years, weight in the surgery group was reduced by a mean of 34.6 kg (95% CI 30.2–39.0) compared with 3.0 kg (95% CI 2.1–8.1) in the lifestyle group. Although both groups had improvements in the quality­ of­life subscore of gene ral health, the surgical group had bet­ter performance in four additional subscores (physical functioning score, self­ esteem, family activities and change in health score), with no difference between the groups for three other subscores. Revisional procedures were required in 28% of the surgical group. The authors commented that although this incidence is within the range of other studies, there might be a need, in adoles­cents, for additional education and supervision of eat­ing to ensure they eat small meals slowly. This approach might help reduce the need for revision. This study was the only one included in the 2015 Cochrane Review of bariatric surgery in adolescents94.

A systematic review with broader inclusion cri­teria than the 2015 Cochrane Review investigated

Red foodsGreater than 20 kcal of the average serving for foods within that food group

• Sweets• Desserts• Fast food• High-fat meat or

meat substitutes

Eaten rarely Examples

Yellow foodsWithin 20 kcal of the average serving for foods within that food group (i.e. fruit = 40 kcal and milk and dairy = 80 kcal)

• Full-fat milk• Whole-grain breads

and cereals

Eaten judiciously Examples

Green foodsLess than 20 kcal of the average serving within that food group

• Fruits• Vegetables• Legumes• Low-fat milk• Lean meat or meat

substitutes

Eaten freely Examples

Fig. 2 | Traffic light diet categories18,36,37,113. Foods are categorized according to high (top panel), moderate (middle panel) or low (bottom panel) caloric density. These categories are used to guide frequency of intake, with the aim to reduce overall calorie intake.

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prospective clinical trials and observational studies of bariatric surgery in patients ≤18 years old published up to early 2014 (reF.95). The review included 37 studies, with 15 being prospective and 1 being the RCT noted in the previous paragraph. The mean BMI loss after LAGB was 11.6 kg/m2 (95% CI 9.8–13.4), compared with 16.6 kg/m2 (95% CI 13.4–19.8) after Roux­ en­Y gas­tric bypass (RYGB) and 14.1 kg/m2 (95% CI 10.8–17.5) after laparoscopic sleeve gastrectomy (LSG). The review authors noted that adverse effects and long­ term com­plications, including nutritional deficiencies, were more frequent and serious after RYGB than the other two procedures, although there were fewer data for LSG, a procedure that has gained prominence more recently than RYGB or LAGB. All forms of surgery resulted in improvements in a range of obesity­ associated com­plications, such as dyslipidaemia and T2DM, and in quality of life.

Subsequent to this systematic review, the 3­year outcomes of the Teen­ Longitudinal Assessment of Bariatric Surgery (Teen­ LABS) study were published. The Teen­ LABS study is a prospectively enrolled study of adolescents undergoing bariatric surgery in five cen­tres in the United States96. A total of 242 patients (75% female patients and 72% white patients) were enrolled, with 67% undergoing RYGB, 28% LSG and 6% LAGB. At 3 years after surgery, there was an overall mean weight loss of 27% (95% CI 25–29) and marked improvement or remission in T2DM, prediabetes, kidney disease, elevated blood pressure and dyslipidaemia as well as improvement in quality­ of­life measures. However, the majority of patients had low iron concentrations and 13% had undergone one or more additional intra­ abdominal procedures. Such findings indicate that there are risks associated with bariatric surgery in this age group and highlight the importance of ensuring that appropriate nutrient supplementation is provided to adolescents after bariatric surgery.

Further high­ quality long­ term studies of bariatric surgery in adolescents are required to monitor potential

surgical and nutritional complications, to determine whether weight and cardiometabolic risk improvements are maintained well into adulthood and to identify which patients benefit most from surgery97.

Clinical guidelinesConsensus guidelines on bariatric surgery in adolescents have been established by various medical professional bodies in several countries11,98–101. In terms of patient characteristics, the recommendations generally cover: a minimum age, usually in mid­ adolescence; the patient to have reached sexual maturity; the presence of severe obe­sity, usually BMI >35 kg/m2 with an obesity­ associated complication, or BMI >40 kg/m2; the persistence of obe­sity despite involvement in a formal multidisciplinary programme of lifestyle modification and pharmaco­therapy; the patient being able to give informed consent; and the adolescent and family being willing to partici­pate actively in the treatment programme and agreeing to ongoing review following the surgery.

Recommendations generally specify that the sur­gery should be performed by a skilled bariatric surgeon affiliated with a team experienced in the medical and behavioural management of adolescents with obesity. The specific recommendations for the type of sur­gery vary depending upon regional expertise but have included LAGB, RYGB and LSG. Finally, in terms of postoperative management and follow­ up, recom­mendations tend to specify the following: that more frequent postoperative follow­ up is generally required with adolescents than with adult patients; that there is a need for ongoing care by a multidisciplinary team; that contraception be considered owing to improved fertility following weight loss; that clinicians be aware that adolescent patients, especially, might not adhere to nutritional supplementation; that very long­ term follow­ up is required; and that the patient should be enrolled in a bariatric surgery registry.

One of the major challenges in many countries is the need to ensure equitable access to such services for affected adolescents, because, in most health systems, bariatric surgery remains largely available only in the private sector, and bariatric surgery services for adoles­cents are sparse25. Thus, specific strategies for the pro­vision of bariatric surgery for adolescents in the public sector are likely to be needed in most jurisdictions.

Treatment of complicationsMany obesity­ associated complications, such as dys­lipidaemia, fatty liver disease and elevated blood pres­sure, will improve following weight loss. Nevertheless, depending on the type and severity of such complica­tions, it might be appropriate to manage these when identified and not to wait until weight loss has occurred, as weight loss might be difficult to achieve12.

During adolescence, the prevalence of individual obesity­ associated complications increases, as does the clustering of such complications. In addition, adoles­cence sees the emergence of components of the met­abolic syndrome and the development of sex­ specific differences in risk factors for cardiovascular disease102. No long­ term data are available in contemporary cohorts

Increased-protein diet

Low-carbohydrate diet

Conventional diet

0 20 40 60 80 100

Carbohydrate Protein Fat

Energy contribution from macronutrient (%)

Energy intake required for weight loss

Fig. 3 | Macronutrient distribution of common diet interventions39,42,43. The percentage of energy contributions from carbohydrate, protein and fat can be manipulated to achieve an energy intake level for weight loss. The purple and green areas indicate overlap between the percentage energy contributions.

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that enable quantification of future combined or specific risk of obesity­ associated complications or the cost of that risk.

Multiple definitions of the metabolic syndrome in ado­lescence exist, all of which have agreed core elements — obesity, dyslipidaemia, abnormal glucose metabo­lism and hypertension — but these vary in the spe­cifics of cut points and reference standards103–106. The International Diabetes Federation definition, which uses age­ specific cut points for the core metabolic elements listed above for 10–16 years of age (adult cut points for those >16 years) and which specifies abdominal obe­sity as defined by waist measure, is probably the most common in use106,107. Concerns about which definition to use, or whether the metabolic syndrome is present or not103–106, should never impede management of the individual components. The prevalence of the met­abolic syndrome rises over the decade of adolescence and might be present in up to 50% of adolescents with obesity, depending on both the definition used and the population being studied103–106.

Medication doses used in the treatment of obesity­ associated complications will be closer to adult rec­ommendations given their body weight. An important adolescent proviso is that some of these medications are not considered safe in pregnancy, and countries vary in their labelling of safety recommendations. Many drugs recommended for the treatment of metabolic morbid­ity in obesity have not been trialled in the reproductive age group; studies of safety in pregnancy will never be undertaken and translating animal exposure results to humans is not always reliable. Given that these newer medications remain the optimal choice for treatment of metabolic complications of obesity, a more nuanced approach than previously used is being advocated by the FDA, which introduced a new labelling system, the PLLR (Pregnancy and Lactation Labelling)108, pub­lished in 2016. The European Medicines Agency is due to release its updated pregnancy guidelines for consul­tation in 2018 (reF.109). TaBle 1 shows data from the cate­gorization system of the Australian Therapeutic Goods Administration (TGA), which provides currently acces­sible and regularly updated110 ratings for some common medications used in the management of obesity and its complications.

The most common obesity­ associated complications in adolescence are primarily related to metabolic abnor­malities and mental health concerns (Fig. 5). Here, we provide a brief overview of the management of the met­abolic complications associated with obesity. Readers are referred to recent reviews or clinical guidelines for details of the management in the context of adolescent obesity, obstructive sleep apnoea111, nonalcoholic fatty liver disease112, slipped capital femoral epiphysis113, depression114 and anxiety115.

The International Society for Paediatric and Adolescent Diabetes (ISPAD) Clinical Guideline acknowledges the limited evidence for diagnosis, man­agement and monitoring of prediabetes and T2DM in adolescents116,117. The prevalence of T2DM varies with ethnicity, with T2DM occurring in 6% of adolescents with diabetes mellitus in the United States and 40% of adolescents with diabetes mellitus in Asia and the Pacific Islands117. The prevalence of insulin resistance is less well characterized, but increasing age and weight, abdom­inal distribution of obesity, the presence of acanthosis nigricans and a family history of T2DM should raise the level of clinical suspicion118. Prediabetes might be tran­sient, coinciding with the insulin resistance often seen in puberty19, with continuing weight gain predicting pro­gression to T2DM. Other than metformin, drugs used in T2DM usually require off­ label use in those under 18 years of age. The rising community prevalence of obesity and the tighter target range for diabetes mellitus control mean that more than one­ third of adolescents with confirmed type 1 diabetes mellitus might also have overweight or obesity119, and metformin could be added to their therapy to address insulin resistance.

In a study published in 2015 that examined trends in dyslipidaemia and hypertension in youth, 20.2% had adverse levels of total and HDL cholesterol and 11.0% had elevated or borderline blood pressure recordings120. The US National Lipid Association121 provides an annual update of lipid­ lowering therapies, hyperlinks to resources and separate recommendations for children, adolescents and adults <21 years of age. The common dyslipidaemias of adolescent obesity are low levels of HDL cholesterol, in which the effective treatments are weight loss and physical activity, and elevated levels of triglycerides. The risk of pancreatitis is increased with

Musculoskeletal• Improved body composition• Increased caloric expenditure and metabolic rate• Improved bone health• Increased skeletal muscle mass

Psychosocial• Improved cognition• Reduced depressive symptoms• Improved academic performance• Better confidence and self-esteem

Functional• Improved physical fitness• Enhanced exercise tolerance• Increased strength and proprioception

Cardiometabolic• Improved insulin sensitivity• Improved blood pressure and endothelial function• Reduced inflammation• Improved lipid profile

Fig. 4 | Benefits of exercise in adolescents with obesity55–62. A range of elements contributes to the musculoskeletal, cardiometabolic, functional and psychosocial health improvements resulting from increased exercise.

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concentrations of triglycerides >5 mmol/l, and if life­style change is ineffective and aggravating factors are excluded, omega­3 fatty acids, niacin or fibrates should be trialled122.

Elevated blood pressure is defined as blood pres­sure (adjusted for age, sex and height) >90th percen­tile to <95th percentile or 120/80 mmHg (whichever is lower), stage 1 hypertension is blood pressure >95th percentile to <95th percentile + 12 mmHg, or 130/80 to 139/89 mmHg (whichever is lower) and stage 2 hyper­tension is blood pressure >95th percentile + 12 mmHg, or >140/90 mmHg (whichever is lower)123. Pharmaco­therapy should not be withheld if weight loss does not occur. The updated 2017 American Academy of Pediatrics guidelines123 provide a management guide and discussion around drug choices.

The Endocrine Society's Clinical Guideline for pol­ycystic ovary syndrome124 considers adolescents sepa­rately. The diagnosis should be based on clinical and/or biochemical hyperandrogenism in the presence of per­sistent oligomenorrhoea and should not rely on multi­cystic ovarian change, which might be developmentally normal. Although obesity and insulin resistance are present in most patients with polycystic ovary syndrome,

insulin resistance at the receptor level is not present in the ovary, and high insulin concentrations drive ovar­ian androgen production and subsequent hirsutism and menstrual cycle disturbances. Metformin prescribed together with the combined oral contraceptive pill might ameliorate any weight gain associated with the use of combined oral contraceptives125.

Access to health careOne of the six major recommendations of the 2016 Report of the WHO Ending Childhood Obesity Commission was the provision of weight management services for both children and young people as part of Universal Health Coverage126. Given that health sys­tems vary considerably between countries and that there is little published on obesity models of care in young people, there will be a range of challenges in the delivery of treatment services for this group. Importantly, the report highlighted the potential for weight bias by health professionals and hence the need for strategies to avoid stigmatization of young people with obesity.

Adolescent obesity can be managed in paediatric or adult care teams. Neither of these approaches is likely to

Table 1 | Medications for the management of obesity and its complications

name indication comments Safety in pregnancy1

Orlistat Obesity Inhibits gut lipase with resulting steatorrhoea with high- fat meals — easy to manipulate

B1

Phentermine Obesity Sympathomimetic amine that has addictive potential. Rejected by some agencies in its combination with topiramate owing to mental health and cardiovascular system concerns

B3

Topiramate Obesity If epilepsy or severe migraine are present, this fulfils prescribing indications. If prescribed off- label, cost might be prohibitive

D

GLP1R agonists Obesity Mostly by daily injection. Nausea and vomiting are significant adverse effects

B3

Metformin Type 2 diabetes mellitus, prediabetes and insulin resistance, polycystic ovary syndrome, acanthosis nigricans and adjunctive treatment for weight loss

Gastrointestinal upset if not up- titrated slowly. Induces ovulation; consider contraception needs. Monitor vitamin B12 levels128

Approved for use (C)

Statins Hypercholesterolaemia (LDL cholesterol) No data on long- term adverse effects, including myopathy and increased risk of type 2 diabetes mellitus

Teratogenic in animals, but risk appears lower in humans (D)

ACE inhibitors and ARBs

Hypertension and diabetic nephropathy Single daily dose and low adverse effect profile improve compliance

Might increase malformation risk and pregnancy loss in second and third trimesters (D)

SSRIs Depression and anxiety in which talking therapy is not successful

Package warnings that these antidepressants may increase risk of suicidal ideation and behaviours

C

COCP Polycystic ovary syndrome: lower oestrogen doses and newer gestagens have fewer adverse effects

COCP- induced weight gain is disputed129. Contraindicated in paralytic migraine or thromboembolism

B3

Australian categories for prescribing medicines in pregnancy: the Australian Therapeutic Goods Administration (TGA) system is currently accessible and regularly updated110, providing ratings from A (the safest drugs to take during pregnancy ; no known adverse reactions) to D (adverse reactions have been found in humans)110. The TGA system provides guidance that aims to assist both clinicians and the women who use the medications and is reliable evidence- based information for patients who use the Internet for health advice. Health professionals should refer to the TGA website for further information (Australian Government Department of Health). Practitioners should also be aware of local approvals and prescribing rules for medications in pregnancy. ACE, angiotensin- converting enzyme; ARBs, angiotensin receptor blockers; COCP, combined oral contraceptive pill; GLP1R , glucagon- like peptide 1 receptor ; SSRIs, selective serotonin reuptake inhibitors.

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be optimal for adolescents, in whom health care is best served by clinicians with expertise in treating adoles­cents and young adults127. Supported transitional care from paediatric to adult care has not been reported in the literature128, which is of concern given the preva­lence of obesity and the need for ongoing management to avoid further weight gain in young adulthood.

ConclusionsThe importance of effective management of adolescent obesity is underscored by its high prevalence in many countries and the short­ term and long­ term impacts of the condition. Although the evidence base for the management of adolescent obesity is growing, more pragmatic clinical trials in young people are needed. These trials are needed because of the acknowledged

challenges in conducting traditional RCTs at this devel­opmental stage and in this condition and because prag­matic trials offer information that informs the real­ world implementation of therapies. Additionally, improved data are needed on how best to manage young people with obesity who are from disadvantaged environments and those from low­ income and middle­ income coun­tries. Finally, it is vital that obesity in young people is not dismissed as being too difficult to be addressed by clinicians. Instead, there should be a recognition of the WHO concept of adolescence as “a key decade in the life­ course” where there is “a second chance in the sec­ond decade” to improve health outcomes and provide high­ quality clinical services1.

Published online xx xx xxxx

Affective disorders, depression and anxietyDepression and anxiety increase in prevalence in adolescence, with a female preponderance. Treatment in adolescents with obesity is along standard lines. Fluoxetine is less likely to be associated with weight gain than the newer antipsychotics, which are associated with weightgain and insulin resistance, and should be avoided.

Benign intracranial hypertensionPatients without visual defects are treated with acetazolamide, a carbonicanhydrase inhibitor.

SkinSkin tags might require physical removal. For intertrigo, keep dry and use topical antifungals. Metformin seems to be effective for acanthosis nigricans, but much of the evidence is case-based.Clinically, this effect might be positive for adolescents and metformin might assist in reduction in BMI in combined obesity treatment regimens.

Lipids and other cardiovascular risk factorsStatins are suggested for nonfamilial hypercholesterolaemia if LDL cholesterol is >4.1 mmol/l and if additional risk factors are present, such as obesity, hypertension and diabetes mellitus. Concerns regarding long-term safety exist, and data in younger patients with secondary lipid disorders are lacking.

Obstructive sleep apnoeaThe American Academy of Pediatrics Clinical Guidelines give the evidence for weight management in obstructive sleep apnoea as grade C. CPAP therapy should be initiated if symptoms and/or signs of objective evidence of obstructive sleep

if adenotonsillectomy is not performed (grade B). Intranasal glucocorticoids might also assist as adjuvant therapy.

HypertensionPreferred agents are thiazide diuretics and/or ACE inhibitors or angiotensin receptor blockers. Once-a-day dosing and a low adverse effect profile make these drugs particularly useful in adolescents.Fatty liver

Weight loss is the only proven therapy. Insulin sensitizers and vitamin E have been used. Insulin resistance, prediabetes and

diabetes mellitusLifestyle intervention is essential in all three conditions. Metformin also has a role in all three conditions. Metformin is a first-line therapy for type 2 diabetes mellitus in adolescents, but medical instability at presentation might require insulin. Continuation of insulin use should be reviewed at regular intervals as weight gain, accompanied by worsening insulin resistance, is an undesirable effect of long-term therapy.

Polycystic ovary syndromeMetformin will produce a more regular menstrual cycle and induce ovulation, of which the adolescent should be warned. Weight loss, physical hair removal, and the combined oral contraceptive pill to suppress ovarian androgen production are all standard therapies. Weight gain induced by the combined oral contraceptive pill might occur in susceptible individuals.

Slipped capital femoral epiphysisHigh index of suspicion if pain and/or limp are present. Orthopaedic intervention.

Strength and balance training might be useful. Pes planus

Supportive shoes and orthotics.

Fig. 5 | Management of comorbidities122,129–134. Obesity- associated complications are multisystemic, and the summarized treatment recommendations should be considered when the complication is identified in conjunction with weight- loss advice. ACE, angiotensin- converting enzyme; CPAP, continuous positive airway pressure.

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Author contributionsAll authors contributed to researching data for the article, discussion of content, writing the article and reviewing and/or editing the manuscript before submission.

Competing interestsThe authors declare no competing interests.

Publisher’s noteSpringer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Review criteriaThis narrative review is based upon data from systematic reviews, review papers and individual studies known to the authors. Other studies were identified by a MEDLINE search of English language papers published up to 2017 using the search terms “obesity” and “adolescent” and then further refined using such terms as “bariatric surgery”, “behaviour therapy”, “drug therapy”, “diet”, “exercise”, “physical activity”, “weight maintenance” or “sleep”. Where appropriate, reviews or studies of obesity treatment involving children or adults were included in the Review. Reference lists of key papers were also checked to identify additional papers of interest. We also searched for clinical guidelines on the management of adolescent obesity. For the latter to be considered, the guidelines had to be developed or endorsed by a national or international health professional body or government agency and available in English.

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