obesity: pathophysiology, risk assessment, and prevalence
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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
Brown WJ et al. Int J Obes 1998;22:520-528.
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
Relationship between BMI and crude percentage of women reporting medical 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
20
15
30
25
35
Back Pain
Brown WJ et al. Int J Obes 1998;22:520-528.
Relationship between BMI and crude percentage of women reporting medical problems, surgical procedures, symptoms, and health care utilization.
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
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