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Obesity and Weight Control


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Obesity and Weight Control

  1. 1. Obesity and Weight Control Exercise Physiology McArdle, Katch, & Katch Chapter 16
  2. 2. Overweight and Obesity <ul><li>Overweight : body weight that exceeds some average for stature, perhaps age. </li></ul><ul><li>Overfat : body fat that exceeds an age- and/or gender appropriate average by some amt. </li></ul><ul><li>Obesity : overfat condition that accompanies components of obese syndrome. </li></ul>
  3. 3. Obese Syndrome Components <ul><li>Glucose intolerance </li></ul><ul><li>Insulin resistance </li></ul><ul><li>Dyslipidemia </li></ul><ul><li>Type 2 diabetes </li></ul><ul><li>Hypertenision </li></ul><ul><li>Elevated plasma leptin concentration </li></ul><ul><li>Increased visceral adipose tissue </li></ul><ul><li>Increased risk of CHD & some cancers </li></ul>
  4. 4. Obesity: A Global Epidemic <ul><li>What is the prevalence of overweight and obesity in the United States? 65% & 31% </li></ul>
  5. 5. Obesity: A Global Epidemic <ul><li>Why is obesity accelerating in developing countries? </li></ul><ul><li>Increased consumption of energy-dense, nutrient poor foods combined with reduced physical activity. </li></ul>
  6. 6. Causes of Obesity <ul><li>Obesity is a long term process. </li></ul><ul><li>Obesity frequently begins in childhood. Obese parents likely have overweight children. </li></ul><ul><li>Regardless of final body weight as adults, overweight children exhibit more illnesses as adults than normal kids. </li></ul>
  7. 7. Causes of Obesity <ul><li>Excessive fatness also develops slowly through adulthood, most weight gain occurring between ages 25 to 44 yrs. </li></ul><ul><li>Typical American man & woman gain .5 to 1.8 lb/year until 60. </li></ul>
  8. 8. Causes of Obesity <ul><li>Overeating and Other Factors </li></ul><ul><li>Factors that predispose a person to gain excessive weight gain. </li></ul><ul><ul><li>Eating patterns Eating environment </li></ul></ul><ul><ul><li>Food packaging Food availability </li></ul></ul><ul><ul><li>Body image Physical inactivity </li></ul></ul><ul><ul><li>Basal body temp Dietary thermogenesis </li></ul></ul><ul><ul><li>Fidgeting Biochemical differences </li></ul></ul><ul><ul><li>Quantity & sensitivity to satiety hormones </li></ul></ul>
  9. 9. Overeating and Other Factors <ul><li>Nutrition transition shifts in dietary structure toward higher energy density with greater fat and added sugars, greater saturated fat, reduced complex CHO and fiber, and reduced fruits & vegetables. </li></ul><ul><li>Food consumption expressed in kCal per capita per day has increased. </li></ul><ul><li>Decreased energy expenditure for all populations of the world. </li></ul>
  10. 10. Causes of Obesity <ul><li>Characteristics of fast food linked to increased adiposity: </li></ul><ul><ul><li>Higher energy density </li></ul></ul><ul><ul><li>Greater saturated fat </li></ul></ul><ul><ul><li>Reduced complex carbohydrates & fiber </li></ul></ul><ul><ul><li>Reduced fruits and vegetables. </li></ul></ul>
  11. 11. Causes of Obesity <ul><li>Genetics plays a role. </li></ul><ul><ul><li>How much variation in weight gain among individuals can be accounted for by genetic factors? </li></ul></ul><ul><ul><li>Largest transmissible variation is cultural. </li></ul></ul>
  12. 12. Causes of Obesity <ul><li>A Mutant Gene? </li></ul><ul><li>What is leptin ? </li></ul><ul><ul><li>A satiety hormone that influences the appetite control in the hypothalamus. </li></ul></ul><ul><ul><li>A defective gene causes inadequate leptin production. </li></ul></ul><ul><ul><li>The brain receives an under assessment of body’s adipose stores & urge to eat. </li></ul></ul>
  13. 13. Causes of Obesity
  14. 14. Causes of Obesity <ul><li>A defective ob gene causes inadequate leptin production. Thus, the brain receives an under assessment of body’s adipose stores and urge to eat. </li></ul><ul><li>In addition to deficient leptin production, scientists also propose the possibility of defective receptor action (via a leptin receptor molecule on brain cells), which increases a person’s resistance to satiety. </li></ul>
  15. 15. Causes of Obesity <ul><li>Physical Activity: an important component </li></ul><ul><li>See chart for children. </li></ul><ul><li>For young & middle aged men, physical activity relates inversely to body fat levels. </li></ul><ul><li>No relationship between caloric intake and body fat levels. </li></ul>
  16. 16. Obesity <ul><li>Health Risks of Obesity </li></ul><ul><ul><li>Primary risk factor for coronary heart disease. </li></ul></ul><ul><ul><li>Associated with HTN, DM, dyslipidemia, & cerebrovascular disease. </li></ul></ul><ul><ul><li>Obesity-related medical complications account for 12% of national health care. </li></ul></ul>
  17. 17. Obesity <ul><li>How Much Fat is TOO Much? </li></ul><ul><li>List three criteria for evaluating a person’s level of fatness. </li></ul><ul><ul><li>% Body Fat </li></ul></ul><ul><ul><li>Fat Patterning </li></ul></ul><ul><ul><li>Fat Cell Size and Number </li></ul></ul>
  18. 18. Percent Body Fat <ul><li>Overfatness corresponds to any body fat value 5% above the average value for age & sex. </li></ul><ul><li>Borderline obesity in young man > 20 & in young woman >30% . </li></ul>> 30 >25 Obese 26-30 21-25 Overfat 18-25 10-20 Good 12-17 5-9 Optimal < 8 < 5 Lean Women Men Standard
  19. 19. Fat Patterning <ul><li>Adipocytes from some locations efficiently capture excess nutrients from the blood-stream for storage, while others accumulate TGs but readily release them for use by other tissues. </li></ul>
  20. 20. Fat Patterning <ul><li>Visceral (intra-abdominal) adipose tissue (VAT) relates to an altered metabolic profile. </li></ul><ul><li>Abdominal fat described as android has higher health risk than gynoid obesity. </li></ul>
  21. 21. Fat Patterning <ul><li>Give an objective standard for establishing male- and female-pattern obesity. </li></ul><ul><ul><li>Male > .95 W:H ratio </li></ul></ul><ul><ul><li>Female > .80 W:H </li></ul></ul>
  22. 22. Fat Cell Number and Size <ul><li>Increases in adipose tissue occurs in two ways: </li></ul><ul><li>Fat cell hypertrophy </li></ul><ul><li>Fat cell hyperplasia </li></ul>
  23. 23. Fat Cell Number and Size <ul><li>After reaching a biological upper limit for fat cell size, cell number becomes a key factor that determines obesity. </li></ul>
  24. 24. Weight Control <ul><li>What is the prognosis for long term weight control? </li></ul><ul><li>Participants who remain in supervised weight loss program regain almost all within 5 years. </li></ul>
  25. 25. Weight Control <ul><li>The Energy Balance Equation </li></ul><ul><li>One pound of fat contains 3,500 kcal </li></ul>
  26. 26. Dieting to Tip Energy Balance <ul><li>Total energy intake (not macronutrient mixture) determines effectiveness of weight loss with diet. </li></ul><ul><li>Rapid weight loss during first few days comes mainly from body water loss and glycogen depletion. </li></ul><ul><li>Continued weight reduction occurs at expense of greater fat loss per unit weight loss. </li></ul>
  27. 27. Dieting to Tip Energy Balance <ul><li>Resting Metabolic Rate Lowered. </li></ul><ul><li>Repeated cycles of weight loss and weight gain may increase the body’s efficiency to conserve energy. </li></ul><ul><li>Could lead to difficulty losing weight. </li></ul>
  28. 28. Fat Cell Size and Number <ul><li>What happens to fat cell size and fat cell number when adults lose weight? </li></ul><ul><ul><li>Fat cells shrink to a size smaller than adipocytes of nonobese people, number remains sames. </li></ul></ul><ul><li>The large # of relatively small adipocytes may relate to appetite control; person craves food, overeats & gains lost weight. </li></ul><ul><li>Total number of fat cells increases 3 general periods: </li></ul><ul><ul><li>Last trimester pregnancy, 1 st year life, adolescence </li></ul></ul>
  29. 29. Fat Cell Size and Number <ul><li>In non-obese subjects with moderate weight gain, adipocyte size increased substantially with no change in cell number. </li></ul><ul><li>Weight gain among severely obese, new adipocytes develop in addition to hypertrophy of existing cells. </li></ul>
  30. 30. Dieting to Tip Energy Balance Initial water retention. Low carbohydrate favors negative balance. High CHO, low fat Requires close supervision.  LBM Decreased energy input assures negative balance. Semi-starvation Expensive and repetitious; difficult to maintain. Low caloric intake favors negative energy balance. Elevated thermic effect. High protein Ketogenic High fat intake contraindicated. Increased ketone excretion removes energy-containing substances from body. Low CHO – ketogenic Disadvantage Principle Method
  31. 31. Exercising to Tip Energy Balance <ul><li>Increased physical activity combined with dietary restraint maintains weight loss more effectively than caloric restriction alone. </li></ul><ul><li>For previously sedentary, overweight, moderate increases in physical activity do not necessarily increase food intake. </li></ul><ul><li>Recommend minimum of 3 days per week. Intensity individualized, minimum 300 kcal/session </li></ul>
  32. 32. Diet Plus Exercise <ul><li>Combining exercise and diet offers a flexible yet effective approach to weight loss. </li></ul><ul><li>Disadvantages of diet alone include loss of lean body tissue, lethargy, possible malnutrition, decrease basal energy expenditure. </li></ul>
  33. 33. Exercising to Tip the Balance <ul><li>Increased physical activity combined with dietary restraint maintains weight loss more effectively than long term diet alone. </li></ul><ul><li>For previously sedentary, overweight individual, moderate increase in physical activity doesn’t necessarily increase intake. </li></ul><ul><li>Recommend minimum of 3 days/week, more frequently better. Minimum 300 kcal/ session. </li></ul>
  34. 34. Diet Plus Exercise <ul><li>The Ideal Combination </li></ul><ul><li>Exercise enhances fat mobilization from body’s adipose depots and fat catabolism by active muscles. </li></ul><ul><li>Protects against protein loss in skeletal muscle and improves insulin sensitivity. </li></ul>
  35. 35. Maintenance of Goal Body Weight <ul><li>Most weight loss occurs during first 6 months. Up to 85% those starting a weight loss program drop & regain. </li></ul><ul><li>Risks from overweight & obesity exceed those from yo-yo dieting. </li></ul>
  36. 36. Maintenance of Goal Weight <ul><li>Selective fat reduction at specific body areas by spot reduction does NOT work. </li></ul><ul><li>Exercise stimulates fatty acid mobilization through hormones and enzyme action that target depots throughout the body. </li></ul>
  37. 37. Gaining Weight <ul><li>Resistance training complemented by well-balanced diet increases muscle mass. </li></ul><ul><li>If all calories consumed in excess of energy requirement during resistance training would go towards muscle growth, 2000 to 2500 extra calories would support 0.5 kg increase in lean tissue. </li></ul>
  38. 38. Conclusions <ul><li>When traveling in Oia, Santorini a Greek Island, EAT , DRINK , and BE HAPPY , for tomorrow you may die. </li></ul><ul><li>If you make it home, exercise often, hard, and a long time. </li></ul>
  39. 39. Illustration References <ul><li>McArdle, William D., Frank I. Katch, and Victor L. Katch. 2000. Essentials of Exercise Physiology 2 nd ed. Image Collection. Lippincott Williams & Wilkins. </li></ul><ul><li>Plowman, Sharon A. and Denise L. Smith. 1998. Digital Image Archive for Exercise Physiology. Allyn & Bacon. </li></ul>