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Evaluating Body Composition

Evaluating Body Composition. Can you “pinch an inch” (or more)?. Body Composition. Exercise and physical training can control body weight and alter body composition Excess body fat lowers aerobic fitness and reduces the ability to perform activities that require jumping and moving quickly

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Evaluating Body Composition

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  1. Evaluating Body Composition Can you “pinch an inch” (or more)?

  2. Body Composition • Exercise and physical training can control body weight and alter body composition • Excess body fat lowers aerobic fitness and reduces the ability to perform activities that require jumping and moving quickly • There is such a thing as “too thin” • Undesirable levels of body composition are associated with public health problems

  3. Body Composition and Mortality Risk

  4. Cardiovascular Diseases Approximately 1/3 of Americans are overweight to the extent that it causes health problems • Hypertension • Diabetes • Heart disease

  5. Cardiovascular Diseases • Between ages 25 and 50, the average American will gain 50 lbs of body weight, almost all fat (2 lbs per year) • The success rate for treating adult obesity is only 25%, less than cancer cure rates

  6. Diabetes • Associated with obesity • Adult-onset (Type II) diabetes • Those who are “apple shaped” are particularly prone • Type II diabetes is showing up in increasing numbers in children

  7. Weight and CV Disease

  8. Weight Change and CV Disease

  9. Breast Cancer • Most common form among women • 1 in 10 women will develop it • 2nd only to lung cancer as a cause of death • Postmenopausal weight gain increased both the risk of breast cancer and mortality risk

  10. Eating Disorders • 90% of eating disorders occur among women • Anorexia nervosa - onset at 14-18 years - 1% of women • Bulimia nervosa - 17-19 years - 1-3% of women; some say 4-19%

  11. Sources of Adult Obesity Going up for both children and adults • More caloric intake than expenditure • Genetic, environmental and psychological factors • Family environment

  12. Parental and Childhood Obesity

  13. Body Density and Percent Body Fat Body weight consists of fat weight and fat-free weight • Percent body fat: The proportion of total weight that is fat weight • Body density: The ratio of body weight and body volume • Overweight: Weight that exceeds the “normal” weight for an individual on the basis of gender, height, and frame • Obesity: The excessive accumulation of fat weight (>30%)

  14. Ways of Measuring Body Composition • Hydrostatic (underwater) weighing • Body plethysmograph • Body mass index (BMI) • Body circumferences • Skinfolds

  15. Hydrostatic (underwater) Weighing • Most common method (gold standard) of measuring body composition • Objective is to measure body volume, which is used with body weight to calculate body density. Percent fat is calculated from body density. • Based on Archimedes principle: “The difference between a person’s weight in air and their weight under water is equal to the weight of the water displaced”

  16. Calculating Body Density • Weight on land • Weight under water • Residual lung volume (.24 for men; .28 for women) • Water density

  17. Density of Water Dw = 1.005932 – (0.0003394 x TW) Where TW = the temperature of the water in centigrade

  18. Computing Body Volume ( ) -Ba Wt - Ww BV = Dw Wt = weight on land (kg) Ww = weight in water (kg) Dw = density of water Ba = air remaining in body (RV + GI)

  19. Computing Body Density ( ) Wt BD = BV Wt = weight on land (kg) BV = body volume

  20. What about this guy? • Body weight (Wt) = 70.15 kg • Underwater weight (Ww) = 3.36 kg • Body’s air (Ba) = 1.2 L (RV = 1.1 + GI tract 0.1 L) • Density of water (Dw) = 0.995678 at 30o C)

  21. Computing % Body Fat Siri’s Equation ( ) 495 - 450 % Fat = BD

  22. Computing Body Volume ( ) 70.15 – 3.36 - 1.2 BV = 0.995678 = 65.88 cc

  23. Computing Body Density ( ) 70.15 BD = 65.88 = 1.065 g/cc

  24. Converting Body Density to Percent Body Fat Two-Component Model: • Fat density = 0.9 g/cc • Fat-free tissue density = 1.1 g/cc Multi-Component Model: Also includes: • Water content (w) • Mineral content (m)

  25. Computing % Body Fat Siri’s Equation ( ) 495 - 450 % Fat = BD

  26. Computing % Body Fat Brozek’s Equation ( ) 457 - 414 % Fat = BD

  27. Racial Differences • Siri and Brozek equations are not accurate for all ethinic groups • Body density of African-American males (1.075 g/cc) is higher than for white males (1.065 g/cc)

  28. Computing % Body Fat Schutte’s Formula for African-Americans 437.4 ( ) - 392.8 % Fat = BD

  29. What about this guy? • Body weight (Wt) = 70.15 kg • Underwater weight (Ww) = 3.36 kg • Body’s air (Ba) = 1.2 L (RV = 1.1 + GI tract 0.1 L) • Density of water (Dw) = 0.995678 at 30o C) • Body Volume (BV) = 65.88 • Body Density (BD) = 1.065

  30. Computing % Body Fat Siri’s Equation ( ) 495 - 450 % Fat = 1.065 = 14.79%

  31. Computing % Body Fat Brozek’s Equation ( ) 457 - 414 % Fat = 1.065 = 15.1%

  32. Computing % Body Fat Schutte’s Formula for African-Americans 437.4 ( ) - 392.8 % Fat = 1.075 = 14.08

  33. Computing % Body Fat Multi-Component Model ( 2.749 ) -(0.727 x w) -(1.146 x m) % Fat = - 2.053 BD

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