Understanding and Improving Body Composition

1. Chapter 11: Understanding and Improving Body Composition

2. Overview of Body Composition • Definitions • Absolute amount of fat & nonfat tissue in body • Ratio of fat to total body mass (TBM) • Common Measures • Fat mass (FM): total mass of all fat in body • Fat-free mass (FFM): total mass of all nonfat tissues in body • Percent body fat (% fat): ratio of TBM to total FM

3. Overview of Body Composition (cont’d) • Two individuals with the same TBM can have different body compositions.

4. Overview of Body Composition (cont’d) • Obesity, Health, and Body Composition • Obesity is at epidemic proportions • Overweight: BMI = 25.0 to 29.9 • Obese: BMI ≥30 • In US: • 300,000 people die each year from obesity-related diseases • 65% of adults are either overweight or obese • 31% are obese • Prevalence of obesity is rapidly increasing

5. Overview of Body Composition (cont’d) • Prevalence of obesity in US has drastically increased from 1995 to 2005.

6. Overview of Body Composition (cont’d) • Diseases Associated With Obesity • Cardiovascular disease & atherosclerosis • Hypertension • Negative effects on blood lipid profile • Type 2 diabetes • Sleep apnea • Osteoarthritis • Complication in pregnancy & surgery • Cancer (uterine, kidney, colorectal, esophageal) • Gallbladder disease

7. Overview of Body Composition (cont’d) • Causes of Obesity • Ingesting more calories than are expended (overeating) • Genetics (inability to produce leptin) • Alterations in appetite control • Physical inactivity • Cultural factors • Abundance of high-calorie, high-fat food readily available • Large portion sizes

8. Overview of Body Composition (cont’d) • Physical Performance and Body Composition • Higher % fat or FM, but same FFM as another: • Increased TBM to carry in physical activities, reducing performance • Decreased relative peak oxygen consumption • Greater FFM is advantage in absolute strength measurements • Any correlation between body composition & physical performance task depends on: • Measure of body composition • Physical performance task examined

9. Overview of Body Composition (cont’d) • Differences in body composition and body size based on sport demands.

10. Overview of Body Composition (cont’d) • Body Size Versus Body Composition • Anthropometry: measurement & study of body size • Body size refers to: • Total body mass • Height or stature • Body circumferences • Bone breadths • Limb lengths • Body size varies greatly between athletes of different sports & impacts performance in some sports & activities

11. Overview of Body Composition (cont’d) • Body Mass Index (BMI) • Ratio of body mass divided by height • Used as a general indicator of health risks associated with: • Obesity • Severe underweight status • % fat • Calculated by either of 2 equations: • BMI (kg/m2) = weight (kg)/height (m2) • BMI (kg/m2) = weight (lb) × 703/height (in2)

12. Classification BMI (kg/m2) Underweight <18.5 Normal 18.5−24.9 Overweight 25.0−29.9 Obesity class I 30.0−34.9 Obesity class II 35.0−39.9 Obesity class III >40.0 BMI Classifications

13. Determining Body Composition • Densitometry • Determination of body composition from body’s density • Body density = TBM/body volume • Determined by: • Hydrostatic weighing (underwater weighing) • Siri equation: % Fat (495/body density) − 450 • Body density varies with body composition • Assumptions involved in this method lead to some error

14. Determining Body Composition (cont’d) • Skinfolds • Pinching & measuring thickness of skin & subcutaneous fat • Performed at specific anatomical sites with special calipers • Convenient & widely used method • Measurements are used to predict body density • Body density is then used in an equation to predict % fat • Less accurate than hydrostatic weighing • Population-specific equations have been developed (men vs. women)

15. Determining Body Composition (cont’d) • Measurement of a skinfold using calipers.

16. Determining Body Composition (cont’d) • Air-Displacement Plethysmography • A densitometry technique using air displacement • Volume of air in empty chamber is known • Person enters chamber, displacing air • Volume of air left in chamber is determined • Body volume = air volume of empty chamber − air volume of occupied chamber • Body volume is used in equations to find body density & % fat • Generally as accurate as hydrostatic weighing, with some differences for specific populations

17. Determining Body Composition (cont’d) • Air-displacement plethysmography equipment.

18. Determining Body Composition (cont’d) • Bioelectrical Impedance • Electrodes are placed 2 or more spots on body • Electrical current is passed between them • Conductance is greater & impedance lower in FFM than in fat • FM, FFM, & total body water are calculated • Several types of equipment are available, with different accuracy • Generally as accurate as the other indirect methods

19. Determining Body Composition (cont’d) • Bioelectrical impedance.

20. Determining Body Composition (cont’d) • Dual-Energy X-Ray Absorptiometry (DEXA) • Uses low-energy x-ray beams & computer software to image body • Can determine general & regional body composition • Highly reliable • Sensitive to small changes in body composition • Significant correlations with hydrostatic weighing • Considered the “gold standard” in the measurement of body composition

21. Determining Body Composition (cont’d) • DEXA method.

22. Determining Body Composition (cont’d) • Other Methodologies • Total body water measures • Nuclear magnetic resonance imaging (MRI) • Ultrasound

23. Determining Body Composition (cont’d) • MRI.

24. Determining Body Composition (cont’d) • Ultrasound imaging.

25. Sex % body fat required by body % body fat of lean athletes % body fat of healthy non-athletes % body fat, unhealthy % body fat, obese Men 3−5 6−13 14−17 18−25 >25 Women 12−14 16−20 21−24 25−31 >32 Changing Body Composition

26. Changing Body Composition (cont’d) • Energy Balance • Ratio of caloric ingestion to caloric expenditure • Caloric expenditure > caloric ingestion = loss in body mass • Caloric expenditure < caloric ingestion = gain in body mass • Total caloric expenditure = resting metabolic rate (RMR) + caloric expenditure of physical activity • Changes in RMR affect total caloric expenditure & FM loss

27. Changing Body Composition (cont’d) • Dieting and Weight Loss Guidelines • Drink sufficient water • Make sensible fat choices • Minimize empty calories • Do not reduce calories too drastically • Keep portions small

28. Changing Body Composition (cont’d) • Effect of Exercise on Body Composition • Can decrease FM, if caloric expenditure > caloric ingestion • Can increase FFM • Can decrease % body fat due to either or both of the above • Estimating energy expenditure depends on many factors: • Body mass • Training intensity • Which muscles are engaged • # of sets & repetitions • Length of rest periods

29. Changing Body Composition (cont’d) • Caloric Expenditure of Resistance and Aerobic Training • Caloric expenditure both during & after training must be measured • Weight & aerobic training sessions of equal length & intensity result in equivalent energy expenditure & fat metabolism • Both aerobic & weight training: • Increase caloric expenditure during activity • Increase resting energy expenditure up to 24−48 hrs after • Weight training offers advantage of increase in FFM & RMR • Combination of dieting & aerobic & weight training most effective

30. Changing Body Composition (cont’d) • Appetite and Exercise • Immediate effect of exercise: decrease in appetite • Decrease in appetite may occur due to: • Elevated blood catecholamine concentrations • Elevated body temperature • Increased environmental temperatures • Hormonal changes: ghrelin, leptin, insulin • Prolonged effect of exercise: overall increase in appetite, due to expenditure of calories

31. Changing Body Composition (cont’d) • Losing Body Mass Wisely • Goals • Lose FM, not FFM • Maintain loss once achieved • Must occur slowly, over time: 1 to 2 lb per week • Combination of diet & exercise • People respond differently to the same diet • 150 to 400 kcal·day-1 should be expended in physical activity • Weight loss diet should supply between 1200 & 1600 kcal·day-1

32. Changing Body Composition (cont’d) • Mean % Fat • Typically lower than normal in athletes • Lower limits • 5% for men • 12% to 14% for women • Different techniques to measure body composition vary in results • Not all athletes will achieve optimal performance at low % fat • Body composition can vary greatly among athletes at different positions in the same sport

33. Severe Weight Loss • Dehydration • Results from rapid weight loss due to fasting, severe restriction • Glycogen is stored with water in body • Release of glycogen with metabolism releases body water • Dehydration of 3% to 4% of TBM decreases aerobic performance • Magnitude of effect on performance depends on the sport

34. Severe Weight Loss (cont’d) • Female Athlete Triad • Syndrome consisting of 3 interrelated conditions affecting female athletes & active women: • Menstrual cycle irregularities • Osteoporosis • Eating disorders: anorexia nervosa & bulimia nervosa • All relate to body composition & diet • Result in decreased performance & increased risk of injury • Athletes displaying signs should be referred for treatment