Evaluating Body Composition

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

2. 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%)

3. Ways of Measuring Body Composition • Hydrostatic (underwater) weighing • Body plethysmograph • Body mass index (BMI) • Body circumferences • Skinfolds • Bioelectrical Impedance Analysis (BIA)

4. Field Measurements of Body Composition • Body Mass Index (BMI) • Body Circumferences - Waist-Hip Ratio (WHR) • Skinfolds

5. Body Mass Index • Weight-height ratio often used in field settings • Typically used in large-scale public health studies ( Weight ) BMI = Height x Height Weight (kg) = weight (lb)/2.2 Height (m) = height (in)/39

6. BMI Criterion Used to Define Overweight (Healthy People 2010)

7. Estimating % Body Fat From BMI Based on a study of 700 black and white men an women using the multi-component model to measure percent body fat +(0.12 x Age) -(11.61 x gender) % Fat = (1.45 x BMI) - 10.02 Female = 0 Male = 1

8. Estimating % Body Fat From BMI Woman: BMI = 24.3, Age 37 years +(0.12 x 37) -(11.61 x 0) % Fat = (1.45 x 24.3) - 10.02 35.48 + 5.40 – 0 – 10.02 = 29.90% Female = 0 Male = 1

9. Body Circumference • Correlated with body composition determined by underwater weighing • Most highly correlated with abdominal and hip regions • Medical research shows that people with central, visceral obesity are at particular risk for developing CV disease, stroke and non-insulin dependent diabetes millitus

10. Waist-Hip Ratio (WHR) ( ) Waist-C WHR= Hip-C Waist - C = Waist circumference measured horizontally at the umbillicus Hip - C = Hip circumference measured at the largest horizontal circumference around the buttocks

11. Health Risk Estimated from BMI and WHR BMIWaist-Hip Ratio – Males Waist-Hip Ratio – Females

12. Skinfold Measurements • Highly correlated with hydrostatically determined body density • Involves measuring a double thickness of subcutaneous fat with a special caliper • Lange, Harpenden, Lafayette

13. Accuracy of Skinfold Measurements • Calipers that conform to the specifications of the Food and Nutrition Board of the National Research Council of the U.S. • Proper training of the technician • Proper site selection

14. Skinfold Sites Always taken on the right side of the body • Chest: Diagonal fold taken between the anterior axillary line and the nipple (1/2 way for men; 1/3 for women) • Axially: A vertical fold on the midaxillary line at the level of the xiphoid process of the sternum • Triceps: A vertical fold on the posterior midline of the upper arm, halfway between the acromion and olecranon processes

15. Skinfold Sites • Subscapula: A fold taken on a diagonal line coming from the verterbral border to 1-2 cm from the inferior angle of the scapula • Abdomen: A vertical fold taken at a lateral distance of approximately 2 cm from the umbilicus • Suprailium: A diagonal fold above the crest of the ilium

16. Skinfold Sites • Thigh: A vertical fold on the anterior aspect of the thigh midway between the hip and knee joints • Medial Calf: The right leg is placed on a bench with the knee flexed at 90o. Take a vertical skinfold on the medial side of the calf approximately at the level of the greatest calf girth.

17. Percent Body Fat From Skinfolds • Regression equations have been developed to do this • Different equations are necessary for men and women because of differences in essential and storage fat Females (3 = Triceps, suprailium, thigh) BD = 1.099421 – (0.0009928 x 3) + 0.00000023 x 32) – (0.0001382 x Age) Males (3 = Chest, abdomen, thigh) BD = 1.10938 – (0.0008267 x 3) + 0.0000016 x 32) – (0.0002574 x Age) Body Density is inserted into Siri’s, Brozek’s or Schuette’s equation to get % body fat

18. Location of Body Fat

19. Estimates of % Fat for Men (chest, abdomen, and thigh) Age in Years

20. % Body Fat for Male and Female Athletes – Selected Sports

21. Adult Body Composition Standards - Men

22. Adult Body Composition Standards - Women

23. Interpreting % Body Fat Standards • High: Seriously overweight to a degree that this can have adverse health consequences • Moderately High: Significantly overweight. Could be high due to measurement inaccuracies. Monitor carefully • Optimal Range: Highly desirable to maintain body composition at this level • Low: Acceptable but there is no reason to seek a lower percent fat level • Very Low: Should be reached only by high-level endurance athletes. This level has its own health risks. Beware of eating disorders.

24. Bioelectrical Impedance Analysis (BIA) • Based on the principle that electrical resistance to a mild electrical current is related to total body water • Total body water and fat-free weight are highly related • Technology is getting better • Accuracy similar to skinfolds

25. Comparison of Methods • Underwater weighing is the “gold standard” • “Body box” needs more validation research • Skinfolds – best option for general use when done properly

26. Skinfold Measurements • Accuracy and reproducibility – very reliable when testers are properly trained • Simplicity and cost – simple and inexpensive • Fat deposits – location of fat is important to health, only anthropometric data can evaluate where the fat exists • Education – can use this to teach people about the concept of excess body fat • Measuring fat – reduction in sum of skinfolds means reduction in subcutaneous body fat

27. Cautions • Touching people, particularly students of the opposite sex • Informing young people, particularly young girls of % body fat can stimulate disordered eating • Recommend using only sum of skinfolds and not % body fat