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Obesity and Weight Control Exercise Physiology McArdle, Katch, & Katch Chapter 16.

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Presentation on theme: "Obesity and Weight Control Exercise Physiology McArdle, Katch, & Katch Chapter 16."— Presentation transcript:

1 Obesity and Weight Control Exercise Physiology McArdle, Katch, & Katch Chapter 16

2 Overweight and Obesity Overweight: body weight that exceeds some average for stature, perhaps age. Overweight: body weight that exceeds some average for stature, perhaps age. Overfat: body fat that exceeds an age- and/or gender appropriate average by some amt. Overfat: body fat that exceeds an age- and/or gender appropriate average by some amt. Obesity: overfat condition that accompanies components of obese syndrome. Obesity: overfat condition that accompanies components of obese syndrome.

3 Obese Syndrome Components Glucose intolerance Insulin resistance Dyslipidemia Type 2 diabetes Hypertenision Elevated plasma leptin concentration Increased visceral adipose tissue Increased risk of CHD & some cancers

4 Obesity: A Global Epidemic Why is obesity accelerating in developing countries? Increased consumption of energy-dense, nutrient poor foods combined with reduced physical activity.

5 Obesity: A Global Epidemic What is the prevalence of overweight and obesity in the United States? 66% & 31% What is the prevalence of overweight and obesity in the United States? 66% & 31% obesity trend

6 2000 Obesity Trends* Among U.S. Adults BRFSS, 1990, 2000, 2010 (*BMI 30, or about 30 lbs. overweight for 54 person) No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% 30%

7 Causes of Obesity Obesity is a long term process. Obesity is a long term process. Obesity frequently begins in childhood. Obese parents likely have overweight children. Obesity frequently begins in childhood. Obese parents likely have overweight children. Regardless of final body weight as adults, overweight children exhibit more illnesses as adults than normal kids. Regardless of final body weight as adults, overweight children exhibit more illnesses as adults than normal kids. You gonna finish that?

8 Causes of Obesity Excessive fatness also develops slowly through adulthood, most weight gain occurring between ages 25 to 44 yrs. Excessive fatness also develops slowly through adulthood, most weight gain occurring between ages 25 to 44 yrs. Typical American man & woman gain.5 to 1.8 lb/year until 60. Typical American man & woman gain.5 to 1.8 lb/year until 60.

9 Causes of Obesity Overeating and Other Factors Overeating and Other Factors Factors that cause human obesity: Factors that cause human obesity: genetics, environmental, metabolic, behavioral, social Factors that predispose a person to gain excessive weight gain. Factors that predispose a person to gain excessive weight gain. Eating patternsEating environment Eating patternsEating environment Food packagingFood availability Food packagingFood availability Body imagePhysical inactivity Body imagePhysical inactivity Basal body tempDietary thermogenesis Basal body tempDietary thermogenesis FidgetingBiochemical differences FidgetingBiochemical differences Quantity & sensitivity to satiety hormones Quantity & sensitivity to satiety hormones

10 Overeating and Other Factors 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. 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. Food consumption expressed in kCal per capita per day has increased. Food consumption expressed in kCal per capita per day has increased. Decreased energy expenditure for all populations of the world. Decreased energy expenditure for all populations of the world.

11 Causes of Obesity Characteristics of fast food linked to increased adiposity: Characteristics of fast food linked to increased adiposity: Higher energy density Higher energy density Greater saturated fat Greater saturated fat Reduced complex carbohydrates & fiber Reduced complex carbohydrates & fiber Reduced fruits and vegetables. Reduced fruits and vegetables.

12 Causes of Obesity Genetics plays a role. Genetics plays a role. How much variation in weight gain among individuals can be accounted for by genetic factors? How much variation in weight gain among individuals can be accounted for by genetic factors? Familial association is not proof of genetic inheritance-families share eating & exercise habits. Familial association is not proof of genetic inheritance-families share eating & exercise habits. Largest transmissible variation is cultural. Largest transmissible variation is cultural.

13 Causes of Obesity A Mutant Gene? A Mutant Gene? What is What is leptin? A satiety hormone that influences the appetite control in the hypothalamus. A satiety hormone that influences the appetite control in the hypothalamus. A defective gene may cause inadequate leptin production. A defective gene may cause inadequate leptin production. The brain receives an under assessment of bodys adipose stores & urge to eat. The brain receives an under assessment of bodys adipose stores & urge to eat.

14 Causes of Obesity Normally leptin blunts the urge to eat when caloric intake maintains ideal fat stores. In essence, leptin availability, or its lack, affects the neurochemnistry of appetite and the brains dynamic wiring to possibly impact appetite and obesity in adulthood. Leptin alone does not determine obesity or explain why some people eat whatever they want and gain little weight while others become overfat with the same caloric intake.

15 Causes of Obesity A defective ob gene causes inadequate leptin production. Thus, the brain receives an under assessment of bodys adipose stores and urge to eat. May be defective leptin receptor action. How does Leptin affect body fat? Stimulates chemicals that suppress appetite Reduce levels of chemicals that stimulate appetite.

16 Causes of Obesity Physical Inactivity: an important component Physical Inactivity: an important component Each hour increase in TV by adolescents 2% increase obesity. Each hour increase in TV by adolescents 2% increase obesity. Adults 15 & over spent average 2.73 hr/day watching TV in Adults 15 & over spent average 2.73 hr/day watching TV in Each hour increase in TV by adults increase risk of death 11%. Each hour increase in TV by adults increase risk of death 11%.

17 Obesity Health Risks of Obesity Health Risks of Obesity Primary risk factor for coronary heart disease. Primary risk factor for coronary heart disease. Associated with HTN, DM, dyslipidemia, & cerebrovascular disease. Associated with HTN, DM, dyslipidemia, & cerebrovascular disease. Obesity-related medical complications account for 10% of national health care. Obesity-related medical complications account for 10% of national health care.

18 Obesity How Much Fat is TOO Much? How Much Fat is TOO Much? List three criteria for evaluating a persons level of fatness. List three criteria for evaluating a persons level of fatness. % Body Fat % Body Fat Fat Patterning Fat Patterning Fat Cell Size and Number Fat Cell Size and Number

19 Percent Body Fat Overfatness corresponds to any body fat value 5% above the average value for age & sex. Overfatness corresponds to any body fat value 5% above the average value for age & sex. Borderline obesity in young man > 20 & in young woman >30%. Borderline obesity in young man > 20 & in young woman >30%. StandardMenWomen Essential Athletic Acceptable Overfat Obese>25 > 30

20 Fat Patterning Adipocytes from some locations (gluteal & femoral) efficiently capture excess nutrients from the blood-stream for storage, while others accumulate TGs but readily release them for use by other tissues.

21 Fat Patterning Visceral (intra- abdominal) adipose tissue (VAT) relates to an altered metabolic profile. Visceral (intra- abdominal) adipose tissue (VAT) relates to an altered metabolic profile. Abdominal fat described as android (apple) has higher health risk than gynoid (pear) obesity. Abdominal fat described as android (apple) has higher health risk than gynoid (pear) obesity.

22 Fat Patterning Give an objective standard for establishing male- and female-pattern obesity. Give an objective standard for establishing male- and female-pattern obesity. Male >.95 W:H ratio Male >.95 W:H ratio Female >.80 W:H Female >.80 W:H

23 Fat Cell Number and Size Increases in adipose tissue occurs in two ways: Increases in adipose tissue occurs in two ways: 1. Fat cell hypertrophy 2. Fat cell hyperplasia

24 Fat Cell Number and Size After reaching a biological upper limit for fat cell size, cell number becomes a key factor that determines obesity. After reaching a biological upper limit for fat cell size, cell number becomes a key factor that determines obesity.

25 Weight Control What is the prognosis for long term weight control? What is the prognosis for long term weight control? Participants who remain in supervised weight loss program regain almost all within 5 years. Participants who remain in supervised weight loss program regain almost all within 5 years.

26 Weight Control One pound of fat contains 3,500 kcal Unbalance the Energy Equation (First Law Thermodynamics) 1. Reduce kcal intake 2. Increase kcal output 3. Reduce intake and increase output

27 Altering the Energy Balance Total energy intake (not macronutrient mixture) determines effectiveness of weight loss with diet. Total energy intake (not macronutrient mixture) determines effectiveness of weight loss with diet. Rapid weight loss during first few days comes mainly from body water loss and glycogen depletion. Rapid weight loss during first few days comes mainly from body water loss and glycogen depletion. Continued weight reduction occurs at expense of greater fat loss per unit weight loss. Continued weight reduction occurs at expense of greater fat loss per unit weight loss.

28 Altering the Energy Balance Resting Metabolic Rate Lowered. Resting Metabolic Rate Lowered. Blunted metabolism conserves energy causing diet to become progressively less effective. Blunted metabolism conserves energy causing diet to become progressively less effective. Could lead to difficulty losing weight. Could lead to difficulty losing weight.

29 Fat Cell Size and Number What happens to fat cell size and fat cell number when adults lose weight? What happens to fat cell size and fat cell number when adults lose weight? Fat cells shrink to a smaller size than adipocytes of nonobese people, number remains same. Fat cells shrink to a smaller size than adipocytes of nonobese people, number remains same. The large # of relatively small adipocytes may relate to appetite control; person craves food, overeats & gains lost weight. The large # of relatively small adipocytes may relate to appetite control; person craves food, overeats & gains lost weight. Total number of fat cells increases 3 general periods: Total number of fat cells increases 3 general periods: Last trimester pregnancy, 1 st year life, adolescence

30 Fat Cell Size and Number In non-obese subjects with moderate weight gain, adipocyte size increased substantially with no change in cell number. In non-obese subjects with moderate weight gain, adipocyte size increased substantially with no change in cell number. Weight gain among severely obese, new adipocytes develop in addition to hypertrophy of existing cells. Weight gain among severely obese, new adipocytes develop in addition to hypertrophy of existing cells.

31 Select a Diet Program MethodPrincipleDisadvantage Low CHO – ketogenic Increased ketone excretion removes energy-containing substances from body. Ketogenic High fat intake contraindicated. High protein Low caloric intake favors negative energy balance. Elevated thermic effect. Expensive, repetitious; difficult to maintain, dehydrates. Semi- starvation Decreased energy input assures negative balance. Possible malnutrition, lethargy, LBM. High CHO, low fat Low carbohydrate favors negative balance. Initial water retention.

32 Exercising to Tip Energy Balance Increased physical activity combined with dietary restraint maintains weight loss more effectively than caloric restriction alone. Increased physical activity combined with dietary restraint maintains weight loss more effectively than caloric restriction alone. For previously sedentary, overweight, moderate increases in physical activity do not necessarily increase food intake. For previously sedentary, overweight, moderate increases in physical activity do not necessarily increase food intake. Recommend minimum of 3 days per week. Intensity individualized, minimum 300 kcal/session Recommend minimum of 3 days per week. Intensity individualized, minimum 300 kcal/session

33 Diet Plus Exercise Combining exercise and diet offers more flexibility for weight loss. Exercise facilitates fat mobilization from adipose depots and fat catabolism. Preserves fat free body mass, blunts decrease in RMR, improves insulin sensitivity.

34 Diet Plus Exercise The Ideal Combination Exercise enhances fat mobilization from bodys adipose depots and fat catabolism by active muscles. Protects against protein loss in skeletal muscle and improves insulin sensitivity.

35 Maintenance of Goal Body Weight Most weight loss occurs during first 6 months. Up to 85% those starting a weight loss program drop & regain. IOM recommend that obese reduce initial body weight by 5% to 15% as realistic.

36 Maintenance of Goal Weight Selective fat reduction at specific body areas by spot reduction does NOT work. Exercise stimulates fatty acid mobilization through hormones and enzyme action that target fat depots throughout the body.

37 Gaining Weight Resistance training complemented by well- balanced diet increases muscle mass. Resistance training complemented by well- balanced diet increases muscle mass. 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. 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. Intense aerobic training will detract from maximal increases in muscle mass. Intense aerobic training will detract from maximal increases in muscle mass.

38 Conclusions When traveling in Oia, Santorini a Greek Island, EAT, DRINK, and BE HAPPY, for tomorrow you may die. If you make it home, exercise often, hard, and a long time.

39 Illustration References McArdle, William D., Frank I. Katch, and Victor L. Katch Essentials of Exercise Physiology 2 nd ed. Image Collection. Lippincott Williams & Wilkins. McArdle, William D., Frank I. Katch, and Victor L. Katch Essentials of Exercise Physiology 2 nd ed. Image Collection. Lippincott Williams & Wilkins. Plowman, Sharon A. and Denise L. Smith Digital Image Archive for Exercise Physiology. Allyn & Bacon. Plowman, Sharon A. and Denise L. Smith Digital Image Archive for Exercise Physiology. Allyn & Bacon.


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