obesity and weight control

Obesity and Weight Obesity and Weight ControlControl

Exercise PhysiologyExercise Physiology

McArdle, Katch, & KatchMcArdle, Katch, & Katch

Chapter 16Chapter 16

Overweight and ObesityOverweight and Obesity OverweightOverweight: body : body

weight that exceeds weight that exceeds some average for some average for stature, perhaps age.stature, perhaps age.

OverfatOverfat: body fat that : body fat that exceeds an age- exceeds an age- and/or gender and/or gender appropriate average appropriate average by some amt.by some amt.

ObesityObesity: overfat : overfat condition that condition that accompanies accompanies components of obese components of obese syndrome.syndrome.

Obese Syndrome ComponentsObese Syndrome Components

Glucose intoleranceGlucose intolerance Insulin resistanceInsulin resistance DyslipidemiaDyslipidemia Type 2 diabetesType 2 diabetes HypertenisionHypertenision Elevated plasma leptin Elevated plasma leptin

concentrationconcentration Increased visceral Increased visceral

adipose tissueadipose tissue Increased risk of CHD Increased risk of CHD

& some cancers& some cancers

Obesity: A Global EpidemicObesity: A Global Epidemic What is the prevalence of overweight and What is the prevalence of overweight and

obesity in the United States? obesity in the United States? 65%65% & 31%& 31%

Obesity: A Global EpidemicObesity: A Global Epidemic

Why is obesity Why is obesity accelerating in accelerating in developing developing countries?countries?

Increased Increased consumption of consumption of energy-dense, energy-dense, nutrient poor foods nutrient poor foods combined with combined with reduced physical reduced physical activity.activity.

Causes of ObesityCauses of Obesity

Obesity is a long term Obesity is a long term process.process.

Obesity frequently Obesity frequently begins in childhood. begins in childhood. Obese parents likely Obese parents likely have overweight have overweight children.children.

Regardless of final Regardless of final body weight as adults, body weight as adults, overweight children overweight children exhibit more illnesses exhibit more illnesses as adults than normal as adults than normal kids.kids.


Excessive fatness Excessive fatness also develops slowly also develops slowly through adulthood, through adulthood, most weight gain most weight gain occurring between occurring between ages 25 to 44 yrs.ages 25 to 44 yrs.

Typical American Typical American man & woman man & woman gain .5 to 1.8 gain .5 to 1.8 lb/year until 60.lb/year until 60.


Overeating and Other FactorsOvereating and Other Factors Factors that predispose a person to Factors that predispose a person to

gain excessive weight gain.gain excessive weight gain. Eating patternsEating patternsEating environmentEating environment Food packagingFood packaging Food availabilityFood availability Body imageBody image Physical inactivityPhysical inactivity Basal body tempBasal body temp Dietary thermogenesisDietary thermogenesis FidgetingFidgeting Biochemical differencesBiochemical differences Quantity & sensitivity to satiety hormonesQuantity & sensitivity to satiety hormones

Overeating and Other FactorsOvereating and Other Factors

Nutrition transition shifts in dietary Nutrition transition shifts in dietary structure toward higher energy structure toward higher energy density with greater fat and added density with greater fat and added sugars, greater saturated fat, sugars, greater saturated fat, reduced complex CHO and fiber, and reduced complex CHO and fiber, and reduced fruits & vegetables.reduced fruits & vegetables.

Food consumption expressed in kCal Food consumption expressed in kCal per capita per day has increased.per capita per day has increased.

Decreased energy expenditure for all Decreased energy expenditure for all populations of the world.populations of the world.


Characteristics of Characteristics of fast food linked to fast food linked to increased adiposity:increased adiposity: Higher energy densityHigher energy density Greater saturated fatGreater saturated fat Reduced complex Reduced complex

carbohydrates & fibercarbohydrates & fiber Reduced fruits and Reduced fruits and

vegetables.vegetables.


Genetics plays a role.Genetics plays a role. How much variation How much variation

in weight gain in weight gain among individuals among individuals can be accounted can be accounted for by genetic for by genetic factors?factors?

Largest Largest transmissible transmissible variation is cultural.variation is cultural.


A Mutant Gene?A Mutant Gene? What is What is leptin?

A satiety hormone that influences the A satiety hormone that influences the appetite control in the hypothalamus.appetite control in the hypothalamus.

A defective gene causes inadequate A defective gene causes inadequate leptin production.leptin production.

The brain receives an under The brain receives an under assessment of body’s adipose stores assessment of body’s adipose stores & urge to eat.& urge to eat.


A defective ob gene A defective ob gene causes inadequate causes inadequate leptin production. leptin production. Thus, the brain Thus, the brain receives an under receives an under assessment of assessment of body’s adipose body’s adipose stores and urge to stores and urge to eat.eat.

In addition to deficient In addition to deficient leptin production, leptin production, scientists also scientists also propose the propose the possibility of possibility of defective receptor defective receptor action (via a leptin action (via a leptin receptor molecule receptor molecule on brain cells), which on brain cells), which increases a person’s increases a person’s resistance to satiety.resistance to satiety.


Physical Activity: an Physical Activity: an important componentimportant component

See chart for children.See chart for children. For young & middle For young & middle

aged men, physical aged men, physical activity relates activity relates inversely to body fat inversely to body fat levels.levels.

No relationship No relationship between caloric intake between caloric intake and body fat levels. and body fat levels.

ObesityObesity

Health Risks of ObesityHealth Risks of Obesity Primary risk factor Primary risk factor

for coronary heart for coronary heart disease.disease.

Associated with HTN, Associated with HTN, DM, dyslipidemia, & DM, dyslipidemia, & cerebrovascular cerebrovascular disease.disease.

Obesity-related Obesity-related medical medical complications complications account for 12% of account for 12% of national health care.national health care.

ObesityObesity

How Much Fat is TOO Much?How Much Fat is TOO Much? List three criteria for evaluating a List three criteria for evaluating a

person’s level of fatness.person’s level of fatness. % Body Fat% Body Fat Fat PatterningFat Patterning Fat Cell Size and NumberFat Cell Size and Number

Percent Body FatPercent Body Fat

Overfatness Overfatness corresponds to any corresponds to any body fat value 5% body fat value 5% above the average above the average value for age & value for age & sex.sex.

Borderline obesity Borderline obesity in young man in young man > 20> 20 & in young woman & in young woman >30%>30%..

StandardStandard MenMen WomeWomenn

LeanLean < 5< 5 < 8< 8

OptimalOptimal 5-95-9 12-1712-17

GoodGood 10-2010-20 18-2518-25

OverfatOverfat 21-2521-25 26-3026-30

ObeseObese >25>25 > 30> 30

Fat PatterningFat Patterning

Adipocytes from Adipocytes from some locations some locations efficiently capture efficiently capture excess nutrients excess nutrients from the blood-from the blood-stream for storage, stream for storage, while others while others accumulate TGs but accumulate TGs but readily release readily release them for use by them for use by other tissues.other tissues.


Visceral (intra-Visceral (intra-abdominal) adipose abdominal) adipose tissue (VAT) relates tissue (VAT) relates to an altered to an altered metabolic profile.metabolic profile.

Abdominal fat Abdominal fat described as described as android has higher android has higher health risk than health risk than gynoid obesity.gynoid obesity.


Give an objective Give an objective standard for standard for establishing male- establishing male- and female-pattern and female-pattern obesity.obesity. Male > .95 W:H ratioMale > .95 W:H ratio Female > .80 W:HFemale > .80 W:H

Fat Cell Number and SizeFat Cell Number and Size

Increases in Increases in adipose tissue adipose tissue occurs in two occurs in two ways:ways:

1.1. Fat cell Fat cell hypertrophyhypertrophy

2.2. Fat cell Fat cell hyperplasiahyperplasia

Fat Cell Number and SizeFat Cell Number and Size

After reaching a After reaching a biological upper biological upper limit for fat cell limit for fat cell size, cell number size, cell number becomes a key becomes a key factor that factor that determines determines obesity.obesity.

Weight ControlWeight Control

What is the prognosis for long term weight What is the prognosis for long term weight control?control?

Participants who remain in supervised weight Participants who remain in supervised weight loss program regain almost all within 5 years.loss program regain almost all within 5 years.

Weight ControlWeight Control

The Energy The Energy Balance Balance EquationEquation

One pound of fat One pound of fat contains 3,500 contains 3,500

kcalkcal

Dieting to Tip Energy BalanceDieting to Tip Energy Balance

Total energy intake (not Total energy intake (not macronutrient mixture) determines macronutrient mixture) determines effectiveness of weight loss with diet.effectiveness of weight loss with diet.

Rapid weight loss during first few Rapid weight loss during first few days comes mainly from body water days comes mainly from body water loss and glycogen depletion.loss and glycogen depletion.

Continued weight reduction occurs at Continued weight reduction occurs at expense of greater fat loss per unit expense of greater fat loss per unit weight loss.weight loss.


Resting Metabolic Resting Metabolic Rate Lowered.Rate Lowered.

Repeated cycles of Repeated cycles of weight loss and weight loss and weight gain may weight gain may increase the body’s increase the body’s efficiency to efficiency to conserve energy.conserve energy.

Could lead to Could lead to difficulty losing difficulty losing weight.weight.

Fat Cell Size and NumberFat Cell Size and Number

What happens to fat cell size and fat cell What happens to fat cell size and fat cell number when adults lose weight?number when adults lose weight? Fat cells shrink to a size smaller than adipocytes Fat cells shrink to a size smaller than adipocytes

of nonobese people, number remains sames.of nonobese people, number remains sames. The large # of relatively small adipocytes The large # of relatively small adipocytes

may relate to appetite control; person may relate to appetite control; person craves food, overeats & gains lost weight.craves food, overeats & gains lost weight.

Total number of fat cells increases 3 general Total number of fat cells increases 3 general periods: periods: Last trimester pregnancy, 1Last trimester pregnancy, 1stst year life, year life,

adolescenceadolescence

Fat Cell Size and NumberFat Cell Size and Number

In non-obese subjects with moderate In non-obese subjects with moderate weight gain, adipocyte size increased weight gain, adipocyte size increased substantially with no change in cell substantially with no change in cell number.number.

Weight gain among severely obese, Weight gain among severely obese, new adipocytes develop in addition new adipocytes develop in addition to hypertrophy of existing cells.to hypertrophy of existing cells.


MethodMethod PrinciplePrinciple DisadvantageDisadvantage

Low CHO Low CHO – – ketogenicketogenic

Increased ketone Increased ketone excretion removes excretion removes energy-containing energy-containing substances from body.substances from body.

KetogenicKetogenic

High fat intake High fat intake contraindicated.contraindicated.

High High proteinprotein

Low caloric intake favors Low caloric intake favors negative energy balance. negative energy balance. Elevated thermic effect.Elevated thermic effect.

Expensive and Expensive and repetitious; repetitious; difficult to difficult to maintain.maintain.

Semi-Semi-starvationstarvation

Decreased energy input Decreased energy input assures negative assures negative balance.balance.

Requires close Requires close supervision. supervision. LBMLBM

High High CHO, low CHO, low fatfat

Low carbohydrate favors Low carbohydrate favors negative balance.negative balance.

Initial water Initial water retention.retention.

Exercising to Tip Energy BalanceExercising to Tip Energy Balance

Increased physical activity combined Increased physical activity combined with dietary restraint maintains weight with dietary restraint maintains weight loss more effectively than caloric loss more effectively than caloric restriction alone.restriction alone.

For previously sedentary, overweight, For previously sedentary, overweight, moderate increases in physical activity moderate increases in physical activity do not necessarily increase food intake.do not necessarily increase food intake.

Recommend minimum of 3 days per week.Recommend minimum of 3 days per week. Intensity individualized, minimum 300 Intensity individualized, minimum 300 kcal/sessionkcal/session

Diet Plus ExerciseDiet Plus Exercise

Combining exercise Combining exercise and diet offers a and diet offers a flexible yet effective flexible yet effective approach to weight approach to weight loss.loss.

Disadvantages of Disadvantages of diet alone include diet alone include loss of lean body loss of lean body tissue, lethargy, tissue, lethargy, possible possible malnutrition, malnutrition, decrease basal decrease basal energy expenditure.energy expenditure.

Exercising to Tip the BalanceExercising to Tip the Balance

Increased physical activity combined with Increased physical activity combined with dietary restraint maintains weight loss dietary restraint maintains weight loss more effectively than long term diet alone.more effectively than long term diet alone.

For previously sedentary, overweight For previously sedentary, overweight individual, moderate increase in physical individual, moderate increase in physical activity doesn’t necessarily increase activity doesn’t necessarily increase intake.intake.

Recommend minimum of Recommend minimum of 33 days/week, days/week, more frequently better. Minimum 300 kcal/ more frequently better. Minimum 300 kcal/ session.session.

Diet Plus ExerciseDiet Plus Exercise

The Ideal CombinationThe Ideal Combination Exercise enhances Exercise enhances

fat mobilization from fat mobilization from body’s adipose body’s adipose depots and fat depots and fat catabolism by active catabolism by active muscles.muscles.

Protects against Protects against protein loss in protein loss in skeletal muscle and skeletal muscle and improves insulin improves insulin sensitivity.sensitivity.

Maintenance of Goal Body WeightMaintenance of Goal Body Weight

Most weight loss Most weight loss occurs during first 6 occurs during first 6 months. Up to 85% months. Up to 85% those starting a those starting a weight loss program weight loss program drop & regain.drop & regain.

Risks from Risks from overweight & obesity overweight & obesity exceed those from exceed those from yo-yo dieting.yo-yo dieting.

Maintenance of Goal WeightMaintenance of Goal Weight

Selective fat reduction Selective fat reduction at specific body areas at specific body areas by spot reduction by spot reduction does does NOTNOT work. work.

Exercise stimulates Exercise stimulates fatty acid mobilization fatty acid mobilization through hormones through hormones and enzyme action and enzyme action that target depots that target depots throughout the body.throughout the body.

Gaining WeightGaining Weight

Resistance training complemented Resistance training complemented by well-balanced diet increases by well-balanced diet increases muscle mass.muscle mass.

If all calories consumed in excess of If all calories consumed in excess of energy requirement during energy requirement during resistance training would go towards resistance training would go towards muscle growth, 2000 to 2500 extra muscle growth, 2000 to 2500 extra calories would support 0.5 kg calories would support 0.5 kg increase in lean tissue.increase in lean tissue.

ConclusionsConclusions

When traveling in Oia, When traveling in Oia, Santorini a Greek Santorini a Greek Island,Island, EATEAT, , DRINKDRINK, , andand BE HAPPYBE HAPPY, , for for tomorrow you may tomorrow you may die.die.

If you make it home, If you make it home, exercise often, exercise often, hard, and a long hard, and a long time.time.

Illustration ReferencesIllustration References

McArdle, William D., Frank I. Katch, McArdle, William D., Frank I. Katch, and Victor L. Katch. 2000. and Victor L. Katch. 2000. Essentials of Exercise Physiology 2Essentials of Exercise Physiology 2ndnd ed. Image Collection. Lippincott ed. Image Collection. Lippincott Williams & Wilkins.Williams & Wilkins.

Plowman, Sharon A. and Denise L. Plowman, Sharon A. and Denise L. Smith. 1998. Digital Image Archive Smith. 1998. Digital Image Archive for Exercise Physiology. Allyn & for Exercise Physiology. Allyn & Bacon.Bacon.

obesity and weight control

Documents