nhanes data

Achieving and MaintainingAchieving and Maintaininga Healthy Body Weighta Healthy Body Weight

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

13

NHANES Data

National Health And Nutrition Examination Survey, 1999-2002

•Indicated an estimated 65% of US adults are either overweight or obese

• This represents a prevalence that is 16% higher than estimates from NHANES, 1988-94

•16% of children 9-16 yoa (~9 million) are overweight

• This is triple the amount from 1980 estimates

www.cdc.gov/nchs/products/pubs/pubd/hestats/obese/obse99.htm

Obesity: Cause for Concern

•Overweight & obesity results from a complex interaction between genes and the environment characterized by long-term energy imbalance

•Major public health challenge as a major contributor to preventive death in the US

Copyright © 1998 NIH Publication No. 98-4083


Obesity

Figure 13.10


Disorders Related to Energy Intake

Overweight and obesity – epidemic in US linked to many chronic diseases:

HypertensionDyslipidemia - elevated total cholesterol,

triglycerides, and LDL cholesterol, and decreased HDL cholesterol

Type 2 diabetesHeart disease and strokeGallbladder disease


Disorders Related to Energy Intake

Overweight and Obesity – epidemic in US linked to many chronic diseases:

Osteoarthritis Sleep apnea Certain cancers: colon, breast, endometrial, and

gallbladder Gestational diabetes, premature fetal deaths, neural tube

defects, and complications during labor and delivery Depression

Why treat obesity?

•Condition substantially raises risk of morbidity and mortality

•Evidence from controlled trials indicates that weight loss reduces risk factors for disease

•Estimated that at any given time 30-40% of population are trying to lose weight

• An estimated $30-40 billion is spent on diet products and self-help books yearly



What is a Healthful Body Weight?

A healthful weight Is appropriate for your age and physical

developmentIs maintained without constant dietingIs based on family history of body shape and

weightPromotes good eating habits and allows for

regular physical activityIs acceptable to you



Underweight: having too little body fat to maintain health (BMI < 18.5 kg/m^2)

Overweight: having a moderate amount of excess body fat (BMI 25-29.9 kg/m^2)



Obese: having an excess of body fat that adversely affects health (BMI 30-39.9 kg/m^2)

Morbid obesity: body weight exceeding 100% of normal, creating a very high risk for serious health consequences (BMI > 40 kg/m^2)


Evaluating Body Weight

A person’s actual weight is not the only factor to consider

Determining if a person’s body weight is healthful should include:

Determining the Body Mass Index (BMI)Measuring body compositionAssessing the pattern of fat distribution



Body Mass IndexExpresses the ratio of a person’s weight to the

square of their heightBMI = weight (kg) / height (m)2

BMI = [weight (lbs) / height (inches)2] X 703BMI values below 18.5 or above 30 have

increased health risksCorrelates with both morbidity & mortality



Figure 13.1



Body compositionMeasure of body fat and lean body massCan be measured by

Underwater weighing Skinfold measurements Bioelectric impedance analysis Near infrared reactance Dual-Energy X-Ray Absorptiometry Bod Pod™



Fat distribution patternApple-shaped fat patterning – upper body

Increased risk for chronic diseases Men tend to store fat in their abdominal region

Pear-shaped fat patterning – lower body No significant increased risk for chronic diseases Women tend to store fat in their lower body



Fat distribution pattern: Abdominal fat increases chronic disease riskWaist-to-hip ratio

Men’s waist-to-hip ratio is higher than 0.90 Women’s is higher than 0.80

Waist circumference Men above 40 in. (or 102 cm.) Woman above 35 in. (or 88 cm.)



Table 13.3


Gaining or Losing Weight

Whether a person gains or loses weight depends on

Energy intake vs. energy expenditureGenetic factorsChildhood weightBehavioral factorsSocial factors


Energy Balance

Energy balanceOccurs when energy intake = energy

expenditureEnergy intake is kcal from foodEnergy expenditure is energy expended at rest

and during physical activity


Energy Intake

When total daily energy intake exceeds the amount of energy they expend, weight gain resultsAn excess intake of approximately 3,500 kcal will result in a gain of one pound

Without exercise, this gain will likely be fat


Energy Expenditure

Energy is expended to maintain basic body functions and to perform activities

Total 24-hour energy expenditure is composed of three components:

Basal metabolic rate (BMR)Thermic effect of food (TEF)Energy cost of physical activity


Energy Expenditure

Direct calorimetry is a method that measures the amount of heat the body releasesIndirect calorimetry estimates energy expenditure by measuring oxygen consumption and carbon dioxide production


Energy Expenditure

Basal Metabolic Rate (BMR)Energy expended to maintain basal, or resting,

functions of the bodyThe highest proportion of total energy

expenditure (60-70%)BMR increases with more lean body mass,

during stress, and periods of growthBMR decreases with age and during energy

restriction


Energy Expenditure

Table 13.4


Energy Expenditure

Thermic Effect of Food (TEF)Energy expended to process foodAbout 5-10% of the energy content of a meal

Energy cost of physical activity About 20-35% of someone’s total energy

output each day


Genetic Factors

About 25% of one’s body fat is accounted for by genetic influences

Different ideas have been suggested to explain the impact of genetics on body fat

Thrifty Gene Theory Set-point Theory


Genetic Factors

Thrifty gene theoryProposes that a gene (or genes) causes people

to be energetically thriftyProposes that people with this gene expend less

energy than other people and therefore gain weight

A “thrifty gene” has not been identified


Genetic Factors

Set-point theoryProposes that each person’s weight stays within

a small range (set point)The body compensates for changes in energy

balance and keeps a person’s weight at their set point


Childhood Factors

Environmental factors in childhood can influenceFood choicesActivity levelsLater adult behaviors

Childhood overweight increases the risk of heart disease and premature death as an adult


Composition of the Diet

Theory states that overeating dietary fat promotes storage as adipose tissue

Overeating carbohydrate or protein will also lead to weight gain

Important to maintain a balanced diet combining fat, carbohydrate, and protein


Physiologic Factors

Hunger vs. appetiteProteins affect the regulation of hunger and storage of body fat

Leptin acts to reduce food intake (feeling of satiety)

Ghrelin stimulates food intakePeptide YY (PYY) decreases appetite Uncoupling proteins in brown adipose tissue

increase energy expenditure


Physiologic Factors

Increase satiety (or decrease food intake) Hormones – serotonin, cholecystokinin (CCK) Increase in blood glucose levels after meal Stomach expansion Nutrient absorption from the small intestine

Decrease satiety (or increase food intake) Hormones - beta-endorphins Neuropeptide Y Decreased blood glucose levels


Social Factors

Social factors influencing our diet include:Family or cultural traditionsHolidays and celebrationsEasy access to high-fat foodsLess physically active lifestylesSocietal expectations of the “perfect” body


Achieve & Maintain Healthful Weight

Healthful weight change requiresGradual change in energy intakeRegular and appropriate physical exerciseApplication of behavior modification

techniques

Set appropriate and realistic goals

•Initial goal of weight loss therapy is to reduce body weight by ~10% from baseline in 6 months of therapy

•Depending on the amount of overweight/obesity a decrease of 500-1000 kcal/day will lead to weight losses of ~1-2 pounds/week

Copyright © 1998 NIH Publication No 98-4083

Set appropriate and realistic goals

•After 6 months, the rate of weight loss usually declines and weight plateaus (changing resting metabolic rates & difficulty adhering to lifestyle)

•Experience reveals that lost weight usually will be regained unless a weight maintenance program consisting of diet therapy, physical activity, and behavior therapy is continued indefinitely



Weight Loss Diets

High-fat, low-carbohydrate, high-protein diets Cause ketosis, which will decrease blood

glucose and insulin levels and reduce appetiteDr. Atkins’ Diet Revolution, Protein Power Nutritionally inadequate, require supplementsSide effects: constipation, diarrhea, nausea,

headaches, ketone breath, insomnia, fatigue


Weight Loss Diets

Moderate-fat, high-carbohydrate, moderate-protein diets

Balanced in nutrients: 20-30% calories from fat, 55-60% carbohydrate, 15-20% protein

Weight Watchers, Jenny Craig, DASH diet, and the USDA MyPyramid

Gradual weight loss (1-2 pounds per week)Typical energy deficits 500-1000 kcal per day


Weight Loss Diets

Low-fat and very-low-fat diets About 11-19% of total energy as fat, while

very-low-fat-diets contain less than 10% Dr. Dean Ornish’s Program for Reversing Heart

Disease and The New Pritikin ProgramEmphasize complex carbohydrates and fiber Regular physical activity is a key component Lower LDL cholesterol, triglyceride, glucose,

insulin levels, and blood pressure



Safe and effective weight loss Follow recommended serving sizesReduce high-fat and high-energy food intakeRegular physical exercise: increase energy

expenditure and BMRStart slow & increase graduallyLong-term goal: accumulate at least 30 minutes of

moderate intensity activity on most, and preferably all, days of the week



Weight loss medications: Many have been removed from marketShould never be used without lifestyle

modificationsHerbal supplements:

Not FDA regulatedRecent “nationwide alert” of tainted weight loss

supplementsCan pose very serious health risks

What do “successful losers” have in common

•The National Weight Control Registry•People volunteered to participate in study if they met criteria of maintenance of at least 30 lb weight loss for at least one year (4000 participants)•Commonly shared features:

• Ate a low-fat, high-carbohydrate diet• Ate breakfast almost every day• Frequent self-monitoring of weight• Had high level of physical activity (~60-90 min mod-intensity

activity every day)

Bariatric Surgery

•May be advisable in those with BMI > 40, or for those with BMI > 35 with other comorbidities, whose efforts at other therapies have failed

• Vertical banded gastroplasty• Gastric bypass• Gastric banding

•Compared to other interventions, surgery has produced the longest period of sustained weight loss




Effective weight gain: Eat 500 to 1,000 extra kcal/day Eat frequently throughout the day Maintain a balanced diet Eat a diet that contains 55% of total energy from

carbohydrate; 25-35% of total energy from fat; and 10-20% of total energy from protein

Avoid tobacco (depress appetite and increase BMR) Exercise regularly with resistance training

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