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Body Composition

Body Composition. Body frame-size (BFS). Female: 10.357*Ht. + (biacromial + bitrochanteric) Male: 8.239*Ht. + (biacromial + bitrochanteric) . Body frame-size (BFS). BFS Limitations. Unvalidated estimates of body frame size Developed primarily from white population

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Body Composition

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  1. Body Composition

  2. Body frame-size (BFS) Female: 10.357*Ht. + (biacromial + bitrochanteric) Male: 8.239*Ht. + (biacromial + bitrochanteric)

  3. Body frame-size (BFS)

  4. BFS Limitations • Unvalidated estimates of body frame size • Developed primarily from white population • Focus on mortality data - not obesity related comorbidities • No assessment of body composition

  5. BMI Body mass (kg)  height (m2) optimal range: 20 -25  or  from optimal range   of disease* * CAD, HTN, CVA, DM, CA, etc.

  6. BMI Determine the BMI for: • Male • weight = 100 kg • height = 2 m

  7. BMI Limitations • fails to consider composition of body • fat

  8. BMI • Generally related to body composition • Highly correlated w/ relative body fat • probably provides a better estimate of obesity

  9. BMI Overweight (1998) • males  27.8  25 • females  27.3  25 • obese: > 30

  10. BMI

  11. BMI

  12. Population Overweight

  13. Population Overweight 1976-80 • 25% of all US adults  20 1988-91 • 33.4% • 47.2% Mexican-American women • 48.6% African-American women

  14. Leanness in Women Active low weight women are at risk of: • delayed onset of menstruation • irregular menstrual cycle (oligomenorrhea) • cessation of menses (amenorrhea)

  15. Leanness in Women Hypotheses: • Exercise Stress (disruption of hypothalamic-pituitary-adrenal) • Energy Availability • energy reserve inadequate to sustain pregnancy • < 17% cessation / 22% normal cycle

  16. Body Composition Models

  17. Body Composition Total Body-Fat (Fat-Mass) = Essential Fat + Storage Fat Essential Fat (survival) • CNS • Bone Marrow • Organs (heart, liver, kidneys, spleen, etc.)

  18. Fat-Free Mass vs. LBM LBM includes essential fat • LBM = Body Mass - Storage Fat FFM excludes essential fat • FFM = Body Mass - Total Body Fat

  19. Behnke Model: Males

  20. Behnke Model: Females

  21. Body Composition 100 kg male w/ 20% body fat • Body mass: 100 kg • Storage Body Fat: 100 * .20 = 20 kg • Lean Body Mass = 100 - 20 = 80 kg - includes 5% essential fat

  22. Body Composition • Fat Free Mass = Body Mass - Total Fat Mass • Total Fat Mass = 20 kg + 4 kg (essential fats) • Fat Free Mass = 100 - 24 = 76 kg

  23. Importance of Body Fat Diet Exercise Combination

  24. Importance of Body Fat

  25. Measuring Body Fat Direct • chemical analysis • dissection Indirect

  26. Measuring Body Fat Hydrostatic Weighing / Densitometry • body volume = loss of weight in H20 (scale wt. - underH2O wt) • “gold standard” • based on assumptions

  27. Measuring Body Fat Skinfolds/Fatfolds Girth Measurements Bioelectrical Impedance Analysis (BIA) • conduction is better thru non-fat •  H20   impedance   % body fat

  28. Measuring Body Fat Near-Infrared Interactance (NIR) • Futrex-5000 • fiber optic • biceps of dominant arm • validity????

  29. Measuring Body Fat US Arm X-Ray (3 site) CT scan MRI DEXA (Dual-energy X-Ray Absorptiometry) - bony mineral content - r = 0.91 - 0.92

  30. Desirable Body Mass Males • strive for 15% • < 20% Females • strive for 25% • < 30%

  31. Desirable Body Mass • 200 lbs. individual • Wants to reduce % body fat from 20%  10% • What is this individual’s desirable weight?

  32. Desirable Body Mass Desirable Body Mass (DSB) = fat-free body mass / (1.00 - desired % fat) Current fat-free body mass = 200 - (200 * 0.20) 160 lbs.

  33. Desirable Body Mass Desirable Body Mass (DSB) = fat-free body mass / (1.00 - desired % fat) DSB = (160 / (1.00 - 0.10) 160 lbs. / .90 178 lbs.

  34. Desirable Body Mass What is the loss in body weight? • 200 lbs. - 178 lbs. = 22 lbs.

  35. General Guidelines for Weight Loss- Athlete • < 2 lbs./week --> preserve FFM • 200 - 500 kcal < daily energy expenditure •  resistance and endurance training

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