Chapter 7: Improving Body Composition ØBody composition is the ratio between fat mass and fat-free mass ØFat-free mass includes all tissues exclusive of fat (muscle, bone, organs, fluids) ØEssential fat is necessary for normal biological function ØEssential fat for men is 3% to 5% of total weight; it is 8% to 12% percent for women

Obesity and Overweight ØObesity is overfatness ØObesity in men is defined as body fat equal to or greater than 25% of total body weight ØObesity in women is defined as body fat equal to or greater than 32% of total body weight ØOverweight is excessive weight for height and does not consider body composition

Regional Fat Distribution ØMost women store fat in the hips, buttocks, thighs, and breasts (gynoid fat) ØMost men store fat in the abdomen, lower back, chest, and nape of the neck (android fat)  Intra-abdominal fat is stored deep in the abdominal cavity and carries a high risk for certain diseases

Methods of Measurement ØHeight-weight tables do not measure body composition ØBody Mass Index (BMI) is weight (kg) divided by height squared (m) ØThe waist-to-hip ratio (WHR) is a simple method for determining body fat distribution ØWaist circumference can also predict disease risk

Regional Fat Distribution (3) ØEnzymes in abdominal fat cells allow these fat cells to be routed directly to the liver for the production of cholesterol ØAbdominal cells are larger than other fat cells; large fat cells are associated with blood glucose intolerance and excessive blood insulin (associated with diabetes)  Excessive blood insulin may promote hypertension

Methods of Measuring Body-Weight Status ØHeight/weight tables do not reflect body composition and are poor instruments for weight-loss recommendations ØBody mass index (BMI) is the ratio of body weight in kilograms to height in meters squared  People with BMIs of 25 to 29.9 are considered overweight; people with BMIs of 30 or higher are considered obese

Measuring Body Composition ØThe only direct way to measure the fat content of humans is through chemical analysis of cadavers ØUnderwater weighing is one of the most accurate indirect measurement techniques  People with more muscle mass weigh more in water than those with less

Measuring Body Composition (2) ØBioelectrical impedance analysis uses a low-level, single-frequency electric current to measure body composition ØSkinfold measurements are one of the most economical ways to measure body composition and, when performed by skilled technicians, correlate well with hydrostatic weighing ØAir-Displacement Plethysmography uses air displacement rather than water displacement for assessing body composition by sitting in the Bod Pod