Obesity: Pathophysiology, Risk Assessment, and Prevalence.

Obesity: Pathophysiology, Risk Assessment, and Prevalence

Obesity

• Excessive amount of body fatExcessive amount of body fat• Women with > 35% body fatWomen with > 35% body fat• Men with > 25% body fatMen with > 25% body fat

• Increased risk for health problems Increased risk for health problems • Are usually overweight, but can have Are usually overweight, but can have

healthy BMI and high % fathealthy BMI and high % fat• Measurements using calipersMeasurements using calipers

Desirable % Body Fat

• Men: 8-25%Men: 8-25%• Women 20-35%Women 20-35%

Regional Distribution• The regional distribution of body fat affects The regional distribution of body fat affects

risk factors for the heart disease and type 2 risk factors for the heart disease and type 2 diabetesdiabetes

Body Fat Distribution: Gynecoid

• Lower-body obesity--Pear shapeLower-body obesity--Pear shape• Encouraged by estrogen and progesteroneEncouraged by estrogen and progesterone• Less health risk than upper-body obesityLess health risk than upper-body obesity• After menopause, upper-body obesity After menopause, upper-body obesity

appearsappears

Body Fat Distribution: Android

• Upper-body obesity--apple shapeUpper-body obesity--apple shape• Associated with more heart disease, HTN, Type Associated with more heart disease, HTN, Type

II DiabetesII Diabetes• Abdominal fat is released right into the liverAbdominal fat is released right into the liver• Encouraged by testosterone and excessive Encouraged by testosterone and excessive

alcohol intakealcohol intake• Defined as waist measurement of > 40” for men Defined as waist measurement of > 40” for men

and >35” for womenand >35” for women

Body Fat Distribution

Weight Management• Balancing energy intake and energy Balancing energy intake and energy

expenditure is the basis of weight expenditure is the basis of weight management throughout lifemanagement throughout life

Set Point Theory

• Body tends to preserve a given weightBody tends to preserve a given weight• Energy expenditure increases and decreases Energy expenditure increases and decreases

with weight loss and gainwith weight loss and gain• Effect may be temporary, e.g. energy needs Effect may be temporary, e.g. energy needs

drop during calorie restriction and drop during calorie restriction and normalize when energy balance is achievednormalize when energy balance is achieved

Components of Energy Expenditure• Resting energy expenditure: expressed as Resting energy expenditure: expressed as

RMRRMR• Energy expended in voluntary activityEnergy expended in voluntary activity• Thermic effect of food (TEF) or diet-Thermic effect of food (TEF) or diet-

induced thermogenesis (DIT)induced thermogenesis (DIT)• Related to energy value of food consumed Related to energy value of food consumed

and adaptive response to overeatingand adaptive response to overeating• TEF may decline as day progresses TEF may decline as day progresses

(Romon, AJCN, 1993)(Romon, AJCN, 1993)

Resting Metabolic Rate

• Increases with increased muscle massIncreases with increased muscle mass• Declines with age Declines with age • Declines during restriction of energy intake Declines during restriction of energy intake

(up to 15%)(up to 15%)• Explains 60-70% of total energy Explains 60-70% of total energy

expenditureexpenditure

Voluntary Energy Expenditure (activity thermogenesis)• The most variable component of energy The most variable component of energy

expenditureexpenditure• Accounts for 15-30% of total Accounts for 15-30% of total • Most of us will require increasing voluntary Most of us will require increasing voluntary

energy expenditure as we age to offset energy expenditure as we age to offset declining fat free mass and RMR in order to declining fat free mass and RMR in order to maintain weightmaintain weight

Role of Brain Neurotransmitters• Neurotransmitters govern the body’s response to Neurotransmitters govern the body’s response to

starvation and dietary intakestarvation and dietary intake• Decreases in serotonin and increases in Decreases in serotonin and increases in

neuropeptide Y are associated with an increase in neuropeptide Y are associated with an increase in carbohydrate appetitecarbohydrate appetite

• Neuropeptide Y increases during deprivation; may Neuropeptide Y increases during deprivation; may account for increase in appetite after dietingaccount for increase in appetite after dieting

• Cravings for sweet high-fat foods among obese Cravings for sweet high-fat foods among obese and bulimic patients may involve the endorphin and bulimic patients may involve the endorphin systemsystem

Hormonal Regulation of Body Weight

• Norepinephrine and dopamine—released Norepinephrine and dopamine—released by sympathetic nervous system in by sympathetic nervous system in response to dietary intakeresponse to dietary intake

• Fasting and semistarvation lead to Fasting and semistarvation lead to decreased levels of these decreased levels of these neurotransmitters—more epinephrine is neurotransmitters—more epinephrine is made and substrate is mobilized.made and substrate is mobilized.

Hormones and Weight

• Hypothyroidism may diminish adaptive Hypothyroidism may diminish adaptive thermogenesisthermogenesis

• Insulin resistance may impair adaptive Insulin resistance may impair adaptive thermogenesisthermogenesis

• Leptin is secreted in proportion to percent Leptin is secreted in proportion to percent adipose tissue and may regulate (decrease) adipose tissue and may regulate (decrease) appetiteappetite

Hunger vs. Satiety

• Satiety—postprandial state when excess food Satiety—postprandial state when excess food is being storedis being stored

• Hunger—postabsorptive state when stores are Hunger—postabsorptive state when stores are being mobilizedbeing mobilized

• Short-term regulation affectedShort-term regulation affected

Hunger vs. Satiety—cont’d• Feedback mechanism with signal from Feedback mechanism with signal from

adipose mass when weight loss occurs—adipose mass when weight loss occurs—eating is the natural result eating is the natural result

• Not always identified in the elderlyNot always identified in the elderly• This occurs mostly in young peopleThis occurs mostly in young people• Long-term regulation affectedLong-term regulation affected

Nature vs Nurture

• Identical twins raised apart have similar Identical twins raised apart have similar weightsweights

• Genetics account for ~40%-70% of weight Genetics account for ~40%-70% of weight differencesdifferences

• Genes affect metabolic rate, fuel use, brain Genes affect metabolic rate, fuel use, brain chemistry, body shapechemistry, body shape

• Thrifty metabolism gene allows for more fat Thrifty metabolism gene allows for more fat storage to protect against famine storage to protect against famine

Nature vs Nurture

Obesity tends to run in familiesObesity tends to run in families• If both parents are normal weight – 10% If both parents are normal weight – 10%

chance of obesity in offspringchance of obesity in offspring• If one parent is obese – 40% chanceIf one parent is obese – 40% chance• If both parents obese – 80% chanceIf both parents obese – 80% chance

Is it genetics or learned eating behavior?Is it genetics or learned eating behavior?

Nurture vs Nature • Environmental factors influence weightEnvironmental factors influence weight• Learned eating habitsLearned eating habits• Activity factor (or lack of)Activity factor (or lack of)• Poverty and obesityPoverty and obesity• Female obesity is rooted in childhood Female obesity is rooted in childhood

obesityobesity• Male obesity appears after age 30Male obesity appears after age 30

Nurture vs Nature

• Overeating learned early in childhoodOvereating learned early in childhood• Bottle vs breastBottle vs breast• Urging children to eat more, clean their Urging children to eat more, clean their

platesplates• Use of food as a rewardUse of food as a reward

Food = Love

Shelly Thorene Photography

Nature and Nurture

• Obesity is nurture allowing nature to Obesity is nurture allowing nature to express itselfexpress itself

• Location of fat is influenced by geneticsLocation of fat is influenced by genetics• A child of obese parents must always be A child of obese parents must always be

concerned about his weightconcerned about his weight

Nature and Nurture

• The influence of The influence of environment is apparent in environment is apparent in the fact that the prevalence the fact that the prevalence of obesity has increased of obesity has increased dramatically in the US in dramatically in the US in the past 40 yearsthe past 40 years

Causes of Obesity

Causes of Excessive Energy Intake

• Active: large portion sizes, frequent meals Active: large portion sizes, frequent meals and snacksand snacks

• Passive: excessive intake of energy-dense Passive: excessive intake of energy-dense foods containing hidden caloriesfoods containing hidden calories

• Variety of options: the greater the variety of Variety of options: the greater the variety of foods offered, the greater the intakefoods offered, the greater the intake• Sensory-specific satiety: as foods are Sensory-specific satiety: as foods are

consumed they become less appealingconsumed they become less appealing

Low Energy Expenditure

• There is a mismatch between our thrifty There is a mismatch between our thrifty metabolic genetic heritage and the sedentary metabolic genetic heritage and the sedentary American lifestyleAmerican lifestyle

Obesity is a Growing Problem

• 127 million adults in the U.S. are 127 million adults in the U.S. are overweight, 60 million obese, and 9 million overweight, 60 million obese, and 9 million severely obese. severely obese.

• 66 percent of U.S. adults are overweight 66 percent of U.S. adults are overweight (BMI(BMI≥≥25)25)

• 32 percent are obese (BMI32 percent are obese (BMI≥≥30)30)• 17% of children and adolescents ages 2-19 17% of children and adolescents ages 2-19

are overweightare overweight

Obesity Trends* Among U.S. AdultsBRFSS

Prevalence of Obesity in Ohio

0

5

10

15

20

25

1991 1995 1998 1999 2000 2001

% of adults

Obesity: A Major Health Issue

• Obesity is the No. 2 preventable cause of death Obesity is the No. 2 preventable cause of death and disability (smoking is #1)and disability (smoking is #1)

• Obesity is associated with increased risk of heart Obesity is associated with increased risk of heart disease, stroke, gallbladder disease, cancer, disease, stroke, gallbladder disease, cancer, osteoarthritis, sleep apneaosteoarthritis, sleep apnea

• Obesity-related health problems cost $75 billion Obesity-related health problems cost $75 billion annually (2003 data)annually (2003 data)

• The public pays about $39 billion a year -- or The public pays about $39 billion a year -- or about $175 per person -- for obesity through about $175 per person -- for obesity through Medicare and Medicaid programsMedicare and Medicaid programs

Health Problems Associated with Excess Body Fat• Surgical riskSurgical risk• Lung (pulmonary) Lung (pulmonary)

diseasedisease• Sleep apneaSleep apnea• HTNHTN• CVDCVD• Bone and joint Bone and joint

disorders (gout, disorders (gout, osteoarthritis)osteoarthritis)

• Type 2 diabetesType 2 diabetes• GallstonesGallstones• Cancers (breast, colon, Cancers (breast, colon,

pancreas, gallbladder)pancreas, gallbladder)• InfertilityInfertility• Pregnancy- difficult Pregnancy- difficult

deliverydelivery• Reduced agilityReduced agility• Early deathEarly death

NHANES III Prevalence of Hypertension* According to BMI

14.9 15.2

22.1

27.727

32.7

41.937.8

0

10

20

30

40

50

Men Women

BMI <25 BMI 25-<27 BMI 27-<30 BMI > 30

*Defined as mean systolic blood pressure 140 mm Hg, mean diastolic 90 mm Hg, or currently taking antihypertensive medication .

Brown C et al. Body Mass Index and the Prevalence of Hypertension and Dyslipidemia. Obes Res. 2000;8:605-619.

Per

cen

t

Obesity and Diabetes Risk

0

20

40

60

80

100

<20 20-25 25-30 30-35 35-40 >40

BMI Levels

Inci

den

ce o

f N

ew C

ases

pe

r 1,

000

Per

son-

Yea

rs

Knowler WC et al. Am J Epidemiol 1981;113:144-156.

Weight Gain and Diabetes Risk

2.11.01.0

5.33.6

2.5

21.1

9.1

6.3

0

5

10

15

20

25

<22 22-23 24+

<5 kg 5-10 kg 11+ kg

Body Mass Index at Age 21

Rel

ativ

e R

isk

Weight Change Since Age 21

Adapted from Chan JM et al. Diabetes Care 1994;17:960-969.

Metabolic Syndrome Criteria*Three or more of the following abnormalities: Three or more of the following abnormalities: • Waist circumference >102 cm (40 inches) in men and Waist circumference >102 cm (40 inches) in men and

> 88 cm (35 inches) in women> 88 cm (35 inches) in women• Serum triglycerides of at least 150 mg/dLSerum triglycerides of at least 150 mg/dL• High density lipoprotein level <40 mg/dL in men and High density lipoprotein level <40 mg/dL in men and

<50 mg/dL in women<50 mg/dL in women• Blood pressure >=135/85 mm/hgBlood pressure >=135/85 mm/hg• Serum glucose >=110 mg/dlSerum glucose >=110 mg/dl• Includes 47 million US residents (27.7% of the Includes 47 million US residents (27.7% of the

populationpopulation

*ATP III Guidelines. National Cholesterol Education Program, 2001

Polycystic Ovary Syndrome (PCOS)

• Endocrine disorder characterized by Endocrine disorder characterized by hyperandrogenism and insulin resistancehyperandrogenism and insulin resistance

• Associated with android obesityAssociated with android obesity• Affects 5-10% of reproductive age womenAffects 5-10% of reproductive age women• Erratic menstrual periods, chronic anovulations Erratic menstrual periods, chronic anovulations

resulting in multiple ovarian cysts; infertility, resulting in multiple ovarian cysts; infertility, acne, hirsutism and alopeciaacne, hirsutism and alopecia

• Increased risk of heart disease, type 2 diabetes, Increased risk of heart disease, type 2 diabetes, reproductive cancersreproductive cancers

Management of PCOS• Symptom oriented, as etiology is unclearSymptom oriented, as etiology is unclear• Individualized diet and exercise plan to Individualized diet and exercise plan to

promote weight loss and normalize insulin promote weight loss and normalize insulin levelslevels

• Medications to alleviate symptomsMedications to alleviate symptoms

26 -Year Incidence of Coronary Heart Disease in Men

177

255

350333366

440

0

100

200

300

400

500

600

<25 25-<30 30+

<50 years 50+ years

Inci

den

ce/1

,000

BMI LevelsAdapted from Hubert HB et al. Circulation 1983;67:968-977. Metropolitan Relative Weight of 110 is a BMI of approximately 25.

26 -Year Incidence of Coronary Heart Disease in Women

76119

179223

268292

0

100

200

300

400

500

<25 25-<30 30+

<50 years 50+ years

Inci

den

ce/1

,000

BMI Levels

Adapted from Hubert HB et al. Circulation 1983;67:968-977. Metropolitan Relative Weight of 110 is a BMI of approximately 25.

Hypertension

BMI

Per

cen

tag

e

20 25 30 35 40

20

10

30

50

40

60

Relationship between BMI and crude percentage of women reportingmedical problems, surgical procedures, symptoms, and health care utilization.

Brown WJ et al. Int J Obes 1998;22:520-528.

BMI

Per

cen

tag

e

20 25 30 35 40

0

10

5

15

Diabetes


Relationship between BMI and crude percentage of women reporting medical problems, surgical procedures, symptoms, and health care utilization.

BMI

Per

cen

tag

e

20 25 30 35 40

5

10

15

25

20

Cholescystectomy



BMI

Per

cen

tag

e

20 25 30 35 40

20

15

30

25

35

Back Pain



Body Mass Index and Mortality Risk

(Adapted from Bray GA. Gray DS, Obesity, part 1: Pathogenesis. West J Med 149:429, 1988; and Lew EA, Garfinkle L; Variations in mortality by weight among 750,000 men and women. J Clin Epidemiol 32:563, 1979.)

BMI and HealthBelow 18.5Below 18.5 UnderweightUnderweight

18.5 – 24.918.5 – 24.9 NormalNormal

25.0 – 29.925.0 – 29.9 OverweightOverweight

Monitor for riskMonitor for risk

30.0 and Above30.0 and Above ObeseObese

Increased health riskIncreased health risk

40.0 and above40.0 and above Severely obeseSeverely obese

Major health riskMajor health risk

Obesity: Pathophysiology, Risk Assessment, and Prevalence.

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