1. Obesity and Physical Activity

2. CHAPTER 22 Overview Obesity –Terminology –Prevalence –Control of body weight –Etiology –Health problems –Treatment –Physical activity

3. Obesity: Terminology and Classification Overweight –Body weight exceeds standard weight for given height and frame size –Not precise terminology –Does not account for body composition Obesity –Excessive body fat (men >25%, women >35%) –Borderline obese: men 20 to 25%, women 30 to 35%

4. Obesity: Terminology and Classification Body mass index (BMI) –Body weight in kilograms/(height in m) 2 –Most widely used standard for obesity classification –Does not account for body composition –Overweight: 25.0 to 29.9 kg/m 2 –Obese: 30.0+ kg/m 2 BMI classification cut points change for difference races and ethnicities

5. Table 22.2

6. Obesity: Prevalence in the United States Prevalence  dramatically since ~1980 –Prevalence of overweight has not changed much –Obesity continues to increase More prevalent in some races and ethnicities –Mexican-American men –Black women Increasing prevalence in children and teens

7. Figure 22.1a

8. Figure 22.1b

9. Figure 22.1c

10. Figure 22.2

11. Figure 22.3

12. Obesity: Prevalence in the United States With age: fat mass , lean body mass  –Over age 25, average person gains ~0.7 to 1 lb per year –Up to 33 extra lb by age 55 Will have significant effect on health care –Earlier onset of obesity –Increasing rates of obesity –Earlier onset of obesity-related diseases

13. Obesity: Worldwide Prevalence Increases in obesity not unique to United States –Canada, Australia, Europe have seen increases to a lesser degree –Available data vary –Most recent studies show obesity spreading to all regions of the world

14. Table 22.3

15. Obesity: Control of Body Weight Body usually carefully balances kilocalorie intake and expenditure –Gain of 1 lb/year represents imbalance of 3,111 kcal per year –Body can balance to within 9 kcal per day Body may regulate around set point using –Resting metabolic rate (RMR) –Thermal effect of meals (TEM) –Thermal effect of activity (TEA)

16. Obesity: Control of Body Weight RMR –Body’s metabolic rate in the early morning –60 to 75% of total energy expenditure TEM –Energy expended to digest, store nutrients, etc. –10% of total energy expenditure –May be defective in obese individuals

17. Obesity: Control of Body Weight TEA –Energy expended to accomplish activities –15 to 30% of total energy expenditure Balance of RMR, TEM, TEA –Helps body adapt to  or  kilocalorie intake –Controlled by sympathetic nervous system –Key for maintaining weight around set point

18. Figure 22.4

19. Obesity: Control of Body Weight Set point regulation versus weight gain –Diet composition alters set point –Physical activity alters set point –High-fat diets usually  overfeeding Other factors –Larger portions/restaurant supersizing –Higher fat consumption –More eating away from home

20. Obesity: Etiology Physiological factors –Heredity/genetics –Hormonal imbalances –Altered basic homeostatic mechanisms Lifestyle factors –Cultural habits –Inadequate physical activity –Improper diets

21. Figure 22.5

22. Obesity: Health Problems Morbidity: presence or rate of disease Mortality: death from disease Obesity and overweight   mortality Major increased risk: BMI >35

23. Figure 22.6

24. Obesity: Health Problems Obesity and overweight associated with –Cardiovascular disease –Type 2 diabetes –Cancer (endometrial, breast, colon) –Liver, gallbladder disease –Osteoarthritis –Sleep apnea Metabolic syndrome rate parallels obesity

25. Obesity: Genetic Versus Lifestyle Effects Pima Indians: study in genetics versus lifestyle Native lifestyle  lean and healthy Western diet/lifestyle  high rates of obesity –Men: 64% –Women: 75% Obesity often accompanied by diabetes –Men: 34% –Women: 41%

26. Obesity: Genetic Versus Lifestyle Effects

27. Obesity: Health Problems Changes in normal body function –Vary with individual –Vary with degree of obesity Lethargy Polycythemia Low blood O 2 /high blood CO 2 Clotting, heart failure

28. Obesity: Health Problems Body fat distribution: disease risk factor –Upper-body (android) obesity (men) –Lower-body (gynoid) obesity (women) Waist:hip girth ratio and visceral fat index identify fat distribution Android obesity  higher risk for –Cardiovascular disease –Elevated blood lipids –Diabetes

29. Figure 22.7

30. Figure 22.8a

31. Figure 22.8b-c

32. Obesity: Health Problems Exacerbates existing diseases Weight loss reduces severity of –Angina pectoris –Hypertension –Congestive heart disease –Heart attack recurrence –Varicose veins –Diabetes –Orthopedic problems

33. Obesity: Health Problems Emotional and psychological factors –Can help cause obesity –Can be exacerbated by obesity Obesity = social stigma –Media glamorize thin people –But norms may shift as obesity becomes more common

34. Obesity: General Treatment Weight loss = kilocalorie intake < kilocalorie expenditure –Oversimplification –Weight loss treatment multifactorial Loss not to exceed 1 to 2 lb per week –Weight loss a long-term project –Maintain balanced diet with caloric deficit –Reduce intake of fat and simple sugars

35. Obesity: General Treatment Hormone treatments –Decrease appetite –Increase RMR –Serious side effects, life threatening Surgical treatments –Intestinal bypass –Gastric banding or bypass –Reserved for most extreme, serious cases

36. Obesity: General Treatment Behavior modification: change in eating patterns or habits. Examples: –Can only eat in one location –No snacking –No second helpings Appealing, simple weight loss approach

37. Obesity: Role of Physical Activity in Weight Control Overeating and inactivity: major causes of obesity Kilocalorie restriction and exercise best treatments Exercise alters body composition –Significant long-term kilocalorie deficit –Significant long-term fat loss EPOC   postexercise metabolism

38. Obesity: Role of Physical Activity in Weight Control Body mass and composition changes with exercise –  Total weight –  Fat mass, percent body fat –Maintained or  FFM Changes long term (6-12 months)

40. Obesity: Role of Physical Activity in Weight Control Both aerobic and resistance training  weight loss –Exercise important aspect of weight loss –Must combine exercise + kilocalorie restriction –Decrease rate of visceral fat accumulation Energy balance equation –Kilocalorie intake – kilocalories excreted = (RMR + TEM + TEA) –Helps clarify weight loss mechanisms

41. Obesity: Role of Physical Activity in Weight Control Exercise effects on appetite –Leads to appetite suppression in male animals –Leads to no change or  intake in female animals –Less activity ≠ less food intake Causes for appetite suppression –Higher circulating catecholamines –Higher body temperature

42. Obesity: Role of Physical Activity in Weight Control Exercise effects on RMR –May increase with training –Resistance training of interest (RMR related to FFM) Exercise effects on TEM –Pre- and postmeal exercise   TEM –Chronic exercise training  inconclusive Exercise effects on fat mobilization –During exercise, FFA mobilization  –Possible causes: hGH, sympathetic stimulation, catecholamines

43. Obesity: Role of Physical Activity in Weight Control Spot reduction a myth –Local exercise ≠ local fat loss –Exercise draws on all fat stores –Local exercise  local muscle development Spot reduction studies –Tennis: dominant versus nondominant arms –Intense sit-up training program

44. Obesity: Role of Physical Activity in Weight Control Low-intensity aerobics and weight loss –High intensity   percent energy from CHO oxidation –Low intensity   percent energy from fat oxidation –Low intensity  no change in total fat kilocalories expended –Low intensity   in total kilocalories expended Fat max zone –Zone where fat oxidation rates near peak –55 to 72% VO 2max

45. Table 22.5

46. Figure 22.9

47. Obesity: Role of Physical Activity in Weight Control Exercise gimmicks ineffective. Examples: –Mark II Bust Developer –Astro-Trimmer Exercise Belt –Slim-Skins Vacuum Pants Reality: exercise and weight loss require work

48. Obesity: Physical Activity and Health Risk Reduction Exercise   risk of disease mortality –Irrespective of weight loss –Good news for those who struggle with weight loss Active lifestyle and fitness more important