Presentation on theme: "Obesity and Weight Control"— Presentation transcript:
1 Obesity and Weight Control Exercise PhysiologyMcArdle, Katch, & KatchChapter 16
2 Overweight and Obesity 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.Obesity: overfat condition that accompanies components of obese syndrome.
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%obesity trend
6 Obesity Trends* Among U.S. Adults BRFSS, 1990, 2000, 2010 (*BMI 30, or about 30 lbs. overweight for 5’4” person)199020002010No Data <10% %–14% %–19% %–24% %–29% ≥30%
7 Causes of Obesity Obesity is a long term process. 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.You gonna finish that?
8 Causes of ObesityExcessive 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.
9 Causes of Obesity Overeating and Other Factors Factors that cause human obesity:genetics, environmental, metabolic, behavioral, socialFactors that predispose a person to gain excessive weight gain.Eating patterns Eating environmentFood packaging Food availabilityBody image Physical inactivityBasal body temp Dietary thermogenesisFidgeting Biochemical differencesQuantity & 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.Food consumption expressed in kCal per capita per day has increased.Decreased energy expenditure for all populations of the world.
11 Causes of ObesityCharacteristics of fast food linked to increased adiposity:Higher energy densityGreater saturated fatReduced complex carbohydrates & fiberReduced fruits and vegetables.
12 Causes of Obesity Genetics plays a role. 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.Largest transmissible variation is cultural.Cultural transmission (or environmental): decrease in average energy expenditure of individuals, related to decreased energy expenditure on the job, in travel to work or school, and in recreational activities. Food availability, snacking patterns, diet composition, and palatability all influence amount of food a person ingests.
13 Causes of Obesity A Mutant Gene? What is leptin? A satiety hormone that influences the appetite control in the hypothalamus.A defective gene may cause inadequate leptin production.The brain receives an under assessment of body’s adipose stores & urge to eat.Defect in two genes.Defect in gene that synthesizes leptin -congenital absence of leptin produced continual hunger & marked obesity.Genetic defect in body’s response to leptin’s signal.
14 Causes of ObesityNormally 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 brain’s 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 ObesityA defective ob gene causes inadequate leptin production. Thus, the brain receives an under assessment of body’s adipose stores and urge to eat.May be defective leptin receptor action.How does Leptin affect body fat?Stimulates chemicals that suppress appetiteReduce levels of chemicals that stimulate appetite.
16 Causes of Obesity Physical Inactivity: an important component Each hour increase in TV by adolescents 2% increase obesity.Adults 15 & over spent average 2.73 hr/day watching TV in 2010.Each hour increase in TV by adults increase risk of death 11%.Estimates children 6-11 average 26 hours TV weekly; adolescents spend about 22 hours TV weekly.Each hour increase TV by adolescents 2% increase obesity prevalence.
17 Obesity Health Risks of Obesity Primary risk factor for coronary heart disease.Associated with HTN, DM, dyslipidemia, & cerebrovascular disease.Obesity-related medical complications account for 10% of national health care.
18 Obesity How Much Fat is TOO Much? List three criteria for evaluating a person’s level of fatness.% Body FatFat PatterningFat Cell Size and Number
19 Percent Body FatOverfatness corresponds to any body fat value 5% above the average value for age & sex.Borderline obesity in young man > 20 & in young woman >30%.StandardMenWomenEssential3-511-14Athletic8-1212-18Acceptable13-2019-25Overfat21-2526-30Obese>25> 30
20 Fat PatterningAdipocytes 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 PatterningVisceral (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.
22 Fat PatterningGive an objective standard for establishing male- and female-pattern obesity.Male > .95 W:H ratioFemale > .80 W:H
23 Fat Cell Number and Size Increases in adipose tissue occurs in two ways:Fat cell hypertrophyFat 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.
25 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.
26 Weight Control One pound of fat contains 3,500 kcal Unbalance the Energy Equation (First Law Thermodynamics)Reduce kcal intakeIncrease kcal outputReduce intake and increase output
27 Altering the Energy Balance 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.Continued weight reduction occurs at expense of greater fat loss per unit weight loss.
28 Altering the Energy Balance Resting Metabolic Rate Lowered.Blunted metabolism conserves energy causing diet to become progressively less effective.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?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.Total number of fat cells increases 3 general periods:Last trimester pregnancy, 1st 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.Weight gain among severely obese, new adipocytes develop in addition to hypertrophy of existing cells.
31 Select a Diet Program Method Principle Disadvantage Low CHO – ketogenicIncreased ketone excretion removes energy-containing substances from body.KetogenicHigh fat intake contraindicated.High proteinLow caloric intake favors negative energy balance. Elevated thermic effect.Expensive, repetitious; difficult to maintain, dehydrates.Semi-starvationDecreased energy input assures negative balance.Possible malnutrition, lethargy, LBM.High CHO, low fatLow 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.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
33 Diet Plus ExerciseCombining 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 body’s 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 WeightResistance 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.Intense aerobic training will detract from maximal increases in muscle mass.
38 ConclusionsWhen 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 2nd ed. Image Collection. Lippincott Williams & Wilkins.Plowman, Sharon A. and Denise L. Smith Digital Image Archive for Exercise Physiology. Allyn & Bacon.