Chapter 28 Body Composition Limitation of Height Weight Table Uses invalidated estimates of body frame sizes Data derived from white populations Specific focus on mortality data that may not reflect obesity related comorbidities Provides no assessment of body composition Extreme muscular development primarily contributes to excess weight The term overweight refers only to a body mass in excess of some standard usually the average mass for a given stature Being above the ideal desired body mass based on mass height tables should not dictate whether someone begins a reducing regimen A better alternative would determine Body Composition using a laboratory technique such as skin fold or underwater weighing Terms and Definitions Adipose Tissue Mass 83 fat 15 water 2 protein Most of it is white adipose cells with single white droplet Mainly triacylglycerol Body Mass Index body mass stature 2 Densitometry Archimedes principle underwater weighing Lean Body Mass FFM plus essential body fat Intra abdominal fat visceral fat in the abdominal cavity Visceral Adipose Tissue VAT Adipose tissue within and surrounding thoracic and abdominal cavities Overweight Overfat condition despite the absence of accompanying body fat measures Refers to a body weight that exceeds some avg for stature and age Frequently accompanies an increase in fat and may coincide with the comorbidities glucose intolerance insulin resistance dyslipidemia and hypertension Obesity Extreme overweight continuum Components of obese syndrome Glucose intolerance insulin resistance dyslipidemia type 2 diabetes hypertension elevated plasma leptin concentrations increased visceral adipose tissue increased risk of coronary heart disease cancer Ways to assess body fat independent of body weight Hydrostatic weighing skinfold girths bioelectrical analysis Dual energy X ray Absorptiometry DXA Excess body fat NOT excess body weight explains the relationship b w above average weight and disease risk Chapter 28 Body Composition Body Mass Index More accurate than estimated based only on height and body mass Relationship with all cause mortality ratio As BMI increases throughout the range of moderate and severe overweight so also does risk increase for cardiovascular complications cancer diabetes Alzheimer s gallstones sleep apnea osteoarthritis and renal diseases 130 million 62 American are over weight or obese 30 5 of this total are obese Overweight persons outnumber persons of desirable weight Accuracy of BMI in diagnosing obesity is limited for individuals in the intermediate BMI ranges particularly in men and in the elderly Like the height weight tables BMI fails to consider the body s proportional composition or the all important component of body fat distribution referred to as fat pattering A high BMI could lead to an incorrect interpretation of over fatness in lean individuals with excessive muscle mass because of genetic makeup or excessive training Composition of the Human Body The reference man is taller heavier skeleton weighs more larger muscle mass and has lower body fat content than the reference woman Hormonal difference play a role Male total fat 15 Storage 12 Essential 3 Men Lower Body Fat Limit lean body mass Body mass storage mass lean body mass Remember that lean body mass includes essential mass 3 for men Marathon runners 1 8 Fat Low Fat Probably revels adaptations for long distance running Female total fat 27 Storage 15 Essential 12 Female Lower Limit Body Mass Includes 12 essential body mass Essential Fat Normal physiologic functioning requires fat heart lungs liver spleen kidneys intestine muscles lipid rich tissues of the central nervous system and bone marrow Heart fat is 5 3 8 6 of its weight in females Sex specific fat part of the essential fat in female Might serve biological important functions for childbearing Storage Fat adipose visceral Lean Body Mass contains essential fat which is present in both genders Fat Free Mass all body mass without all extractable fat Chapter 28 Body Composition FFM Body mass Fat Mass In healthy hydrated humans lean body mass and free fatty mass differ only in Essential Fat component Minimal Body Mass women Essential fat sex specific essential fat muscle water and bone Low Weight or Appearance sport is correlated with 1 Delayed onset of menstruation 2 Irregular menstrual cycles 3 Complete cessation of menses Amenorrhea 1 3 to of endurance athletes experience some menstrual irregularity Exercise Stress Hypothesis Prolonged level of exercise may disrupt the Hypothalamic pituitary adrenal and Gonadroping releasing axis which results in irregular menstruation Energy Availability Hypothesis Energy fat reserves are inadequate to sustain pregnancy induce cessation of ovulation Optimal Lean to fat ratio is important to normal menstruation function Peripheral fat converts androgens to estrogen through adipose s role of Leptin production fat levels and appetite control Positive side effect of amenorrhea Less menstrual cycles less risk for reproductive system and non reproductive system cancer b c they produce LESS ESPTROGEN Common Techniques To Assess Body Composition Approaches to determine body composition Direct assessments 1 Cadaver dissolve body in chemical solution 2 Physically dissect fat Indirect Assessments Underwater weighing Skin fold X ray etc Hydrostatic Weighing Determine body volume Body volume equals loss of weight in water with the appropriate temperature correction for water s density Repeated 8 12 times to obtain accurate score Even after a forced maximal exhalation residual lung volume remains Calculations require subtracting the buoyant effect of residual lung volume measured immediately before during or following the underwater weighing Failure to account for residual lung volume will result in a lower body density which will result in a fatter person or higher percent body fat Low density more fat Higher density more muscle Chapter 28 Body Composition Some females experience increase in body water 1kg during menstruation Water retention of this magnitude affects body density and causes small error when computing body fat percent Mass volume density Consuming 800ml of carbonated beverages increases gastric volume underestimates density and causes 11 higher body fat percentage Abdominal gas and sinus air can be ignored residual lung volume must be taken into account Percent body fat 495 body density 450 BOD POD 3 5 min test High reproducibility Determine body volume by
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