Body Composition

Chapter 18

Methods of Determining If an Individual Is Obese

• Metropolitan Life Insurance Company’s height/weight tables– Percentage above recommended weight

• Body mass index (BMI)

• Problems w/ these methods

Body Composition Measurement

• Total body water (TBW)– Isotope dilution– Bioelectrical impedance analysis (BIA)

• Bone density– Photon absorptiometry

• Lean tissue mass– Potassium-40

• Whole body Density– Underwater weighing

• Thickness of various tissues– Skinfolds– Ultrasound – Radiography

Models of Body Composition

• 2-component

• 3-component

• 4-component

The 2-component Model

• Underwater weighing– Based on Db

– Use equation to convert Db to %fat based on age, gender & race

• Skinfolds– Thickness of subcutaneous fat is measured

Underwater Weighing

Body Fatness for Health & Fitness

• Recommended BF– Males

– Females

• Health concerns

Obesity As a Risk Factor

• Primary contributing factor

• Secondary contributing factor– Endometrial cancer

• Associated w/ (not caused by obesity)

Obesity:Definition & Prevalence

• Definition– Men

– Women

• Prevalence in U.S.

Obesity:Benefits of Weight Loss

• Obesity is associated w/:

• If everyone achieved optimal weight

Obesity:Fat Cell Size vs. #

• 25 billion fat cells in normal-weight individual

Obesity:Fat Cell Size & #

Obesity: Genetic & Cultural Factors

• Genetic factors

• Cultural factors

Set Point & Obesity

• The tendency of an individual to return to a certain weight following weight loss suggests there is a biological set point for body weight

• Physiological set point model

• Cognitive set point model

Physiological Set Point

Energy Balance

• Static energy balance

• Dynamic energy balance

∆ of energy stores

energy intake

energy expenditure= -

rate of ∆ of energy stores

rate of ∆ of energy intake

rate of ∆ ofenergy expenditure

= -

Nutrient Balance

• CHO & PRO

• Fat

The Food Quotient

• Food quotient (FQ)

• Respiratory quotient (RQ)

The FQ, RQ & Nutrient Balance

• RQ = FQ

• RQ > FQ

• RQ < FQ

Diet & Weight Control

• Diets high in fat are linked to obesity

• Calories count & must be considered!

Basal Metabolic Rate (BMR)

• Rate of EE under standardized conditions

• Represents 60-75% total EE

• Reduced in response to reduced caloric intake (dieting or fasting)

Thermogenesis

• “Heat generation” associated w/:– Ingestion of meals (thermic effect of feeding)

– Brown adipose tissue– “Futile cycles”

• Metabolic cycles (NA+/K+ pump activity)

Physical Activity

Effect of Exercise on Appetite

• Most humans

Exercise & Body Composition

• Individuals who exercise generally have lower body weight & %fat

• Weight loss in conjunction w/ exercise

Weight Loss vs. Weight Maintenance

• Weight loss

• Weight maintenance– Light to moderate exercise

– Moderate exercise

– Vigorous exercise

Diet, Exercise, & Weight Control

• Energy and nutrient balance is more easily achieved on a low fat diet

• Exercise s the chance that energy balance will be achieved

• Exercise promotes health-related benefits d fitness, HDL cholesterol