Obesity: Pathophysiology, Risk Assessment, and Prevalence

1. Obesity: Pathophysiology, Risk Assessment, and Prevalence

2. Obesity • Excessive amount of body fat • Women with > 35% body fat • Men with > 25% body fat • Increased risk for health problems • Are usually overweight, but can have healthy BMI and high % fat • Measurements using calipers

3. Desirable % Body Fat • Men: 8-25% • Women 20-35%

4. Regional Distribution • The regional distribution of body fat affects risk factors for the heart disease and type 2 diabetes

5. Body Fat Distribution: Gynecoid • Lower-body obesity--Pear shape • Encouraged by estrogen and progesterone • Less health risk than upper-body obesity • After menopause, upper-body obesity appears

6. Body Fat Distribution: Android • Upper-body obesity--apple shape • Associated with more heart disease, HTN, Type II Diabetes • Abdominal fat is released right into the liver • Encouraged by testosterone and excessive alcohol intake • Defined as waist measurement of > 40” for men and >35” for women

7. Body Fat Distribution

8. Weight Management • Balancing energy intake and energy expenditure is the basis of weight management throughout life

9. Set Point Theory • Body tends to preserve a given weight • Energy expenditure increases and decreases with weight loss and gain • Effect may be temporary, e.g. energy needs drop during calorie restriction and normalize when energy balance is achieved

10. Components of Energy Expenditure • Resting energy expenditure: expressed as RMR • Energy expended in voluntary activity • Thermic effect of food (TEF) or diet-induced thermogenesis (DIT) • Related to energy value of food consumed and adaptive response to overeating • TEF may decline as day progresses (Romon, AJCN, 1993)

11. Resting Metabolic Rate • Increases with increased muscle mass • Declines with age • Declines during restriction of energy intake (up to 15%) • Explains 60-70% of total energy expenditure

12. Voluntary Energy Expenditure (activity thermogenesis) • The most variable component of energy expenditure • Accounts for 15-30% of total • Most of us will require increasing voluntary energy expenditure as we age to offset declining fat free mass and RMR in order to maintain weight

13. Role of Brain Neurotransmitters • Neurotransmitters govern the body’s response to starvation and dietary intake • Decreases in serotonin and increases in neuropeptide Y are associated with an increase in carbohydrate appetite • Neuropeptide Y increases during deprivation; may account for increase in appetite after dieting • Cravings for sweet high-fat foods among obese and bulimic patients may involve the endorphin system

14. Hormonal Regulation of Body Weight • Norepinephrine and dopamine—released by sympathetic nervous system in response to dietary intake • Fasting and semistarvation lead to decreased levels of these neurotransmitters—more epinephrine is made and substrate is mobilized.

15. Hormones and Weight • Hypothyroidism may diminish adaptive thermogenesis • Insulin resistance may impair adaptive thermogenesis • Leptin is secreted in proportion to percent adipose tissue and may regulate (decrease) appetite

16. Hunger vs. Satiety • Satiety—postprandial state when excess food is being stored • Hunger—postabsorptive state when stores are being mobilized • Short-term regulation affected

17. Hunger vs. Satiety—cont’d • Feedback mechanism with signal from adipose mass when weight loss occurs—eating is the natural result • Not always identified in the elderly • This occurs mostly in young people • Long-term regulation affected

18. Nature vs Nurture • Identical twins raised apart have similar weights • Genetics account for ~40%-70% of weight differences • Genes affect metabolic rate, fuel use, brain chemistry, body shape • Thrifty metabolism gene allows for more fat storage to protect against famine

19. Nature vs Nurture Obesity tends to run in families • If both parents are normal weight – 10% chance of obesity in offspring • If one parent is obese – 40% chance • If both parents obese – 80% chance Is it genetics or learned eating behavior?

20. Nurture vs Nature • Environmental factors influence weight • Learned eating habits • Activity factor (or lack of) • Poverty and obesity • Female obesity is rooted in childhood obesity • Male obesity appears after age 30

21. Nurture vs Nature • Overeating learned early in childhood • Bottle vs breast • Urging children to eat more, clean their plates • Use of food as a reward

22. Food = Love Shelly Thorene Photography

23. Nature and Nurture • Obesity is nurture allowing nature to express itself • Location of fat is influenced by genetics • A child of obese parents must always be concerned about his weight

24. Nature and Nurture • The influence of environment is apparent in the fact that the prevalence of obesity has increased dramatically in the US in the past 40 years

25. Causes of Obesity

26. Causes of Excessive Energy Intake • Active: large portion sizes, frequent meals and snacks • Passive: excessive intake of energy-dense foods containing hidden calories • Variety of options: the greater the variety of foods offered, the greater the intake • Sensory-specific satiety: as foods are consumed they become less appealing

27. Low Energy Expenditure • There is a mismatch between our thrifty metabolic genetic heritage and the sedentary American lifestyle

28. Obesity is a Growing Problem • 127 million adults in the U.S. are overweight, 60 million obese, and 9 million severely obese. • 66 percent of U.S. adults are overweight (BMI≥25) • 32 percent are obese (BMI≥30) • 17% of children and adolescents ages 2-19 are overweight

29. Obesity Trends* Among U.S. AdultsBRFSS

30. Prevalence of Obesity in Ohio

31. Obesity: A Major Health Issue • Obesity is the No. 2 preventable cause of death and disability (smoking is #1) • Obesity is associated with increased risk of heart disease, stroke, gallbladder disease, cancer, osteoarthritis, sleep apnea • Obesity-related health problems cost $75 billion annually (2003 data) • The public pays about $39 billion a year -- or about $175 per person -- for obesity through Medicare and Medicaid programs

32. Surgical risk Lung (pulmonary) disease Sleep apnea HTN CVD Bone and joint disorders (gout, osteoarthritis) Type 2 diabetes Gallstones Cancers (breast, colon, pancreas, gallbladder) Infertility Pregnancy- difficult delivery Reduced agility Early death Health Problems Associated with Excess Body Fat

33. NHANES III Prevalence of Hypertension* According to BMI Percent *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.

34. Obesity and Diabetes Risk Incidence of New Cases per 1,000 Person-Years BMI Levels Knowler WC et al. Am J Epidemiol 1981;113:144-156.

35. Weight Gain and Diabetes Risk Weight Change Since Age 21 Relative Risk Body Mass Index at Age 21 Adapted from Chan JM et al. Diabetes Care 1994;17:960-969.

36. Metabolic Syndrome Criteria* Three or more of the following abnormalities: • Waist circumference >102 cm (40 inches) in men and > 88 cm (35 inches) in women • Serum triglycerides of at least 150 mg/dL • High density lipoprotein level <40 mg/dL in men and <50 mg/dL in women • Blood pressure >=135/85 mm/hg • Serum glucose >=110 mg/dl • Includes 47 million US residents (27.7% of the population *ATP III Guidelines. National Cholesterol Education Program, 2001

37. Polycystic Ovary Syndrome (PCOS) • Endocrine disorder characterized by hyperandrogenism and insulin resistance • Associated with android obesity • Affects 5-10% of reproductive age women • Erratic menstrual periods, chronic anovulations resulting in multiple ovarian cysts; infertility, acne, hirsutism and alopecia • Increased risk of heart disease, type 2 diabetes, reproductive cancers

38. Management of PCOS • Symptom oriented, as etiology is unclear • Individualized diet and exercise plan to promote weight loss and normalize insulin levels • Medications to alleviate symptoms

39. 26 -Year Incidence of Coronary Heart Disease in Men Incidence/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.

40. 26 -Year Incidence of Coronary Heart Disease in Women Incidence/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.

41. Hypertension 60 50 40 Percentage 30 20 10 20 25 30 35 40 BMI 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.

42. Diabetes 15 10 Percentage 5 0 20 25 30 35 40 BMI 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.

43. Cholescystectomy 25 20 Percentage 15 10 5 20 25 30 35 40 BMI 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.

44. Back Pain 35 30 Percentage 25 20 15 20 25 30 35 40 BMI 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.

45. 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.)

46. BMI and Health