Body composition and weight management

Body composition

Body composition refers to the makeup of tissues of the body-often used in reference to %body fat

Two-compartment model of body composition

Fat mass and Fat-free mass

BMI (Body mass index) equation

Weight(kg)/height²(m)

Classification for adults

Underweight: BMI <18.5 kg/m²

Normal BMI 18.5-24.9 kg.m²

Overweight BMI 25.0-29.9kg/m²

obesity BMI >or= 30.0kg/m²

Classification for children

•Overweight: BMI ≥85th percentile for age and gender

•Obese: : BMI ≥95th percentile for age and gender

A muscular individual could be classified as obese for BMI

True

What is SEE

Standard error of the estimate

Measure of variation between predicted value and the true value

Five methods are commonly used to evaluate of body composition

Underwater weighing

Air displacement plethysmography

Dual energy x-Ray Absorptiometry (DEXA)

Bioelectrical impedance analysis (BIA)

Sum of skinfolds

What is a similarity between underwater weighing and air displacement plethysmography

Both methods measure body volume to calculate density to estimate %body fat

equation for body composition

Density=mass/volume

•Body fat is divided into fat-free and fat mass

•Fat mass density = 0.900

•Fat-free mass density = 1.100

%Body fat=

(495/density)-450

What’s the underwater weighting and air displacement plethysmography SEE=

2.7/ air 2.2 to 3.7

Dual energy X-ray absorptiometry (DEXA)

•Two X-ray beams are used to determine whole body and regional estimates of lean tissue, bone density, and fat

Popular but has advantages

What’s the SEE of the DEXA

1.8%

What’s a disadvantage of the DEXA

expensive

certified medical personnel must perform the scan

BIA to estimate body composition

•Principle of operation: a small electrical current is applied to one extremity, and the voltage drop (impedance) is measured at another extremity

Lean tissue

•mostly water and electrolytes) is a good conductor of electricity (low impedance)

Fat tissue

•is a poor conductor of electricity (high impedance)

Impedance value provides what

estimate of total body water from which both fat-free and fat mass can be calculated (S E E = 3.5 to 5%)

Skin fold estimates what

body composition

Predication of body density from estimation of subcutaneous fat (20 to 70%) of total fat)

Skinfold SEE=

3.5%

Skin fold sites

3-site

Male

Chest, Abdomen, Thigh

Female

Triceps, Suprailiac, Thigh

Healthy ranges of percent body fat

Weight loss

role of diet and exercise

Since obesity is increasing what other diseases increase

cardiovascular disease, diabetes, and cancers

Key to successful weight management program lies in

Understanding of control of body energy stores

Energy balance equation

Components of daily energy expenditure

Macronutrient storage component of the energy balance equation of the energy balance reflects body stores of

carbs,protein,and fat

•Fat stored as triglycerides primarily in

white adipocytes, but 3 types of fat cells exist

Proteins exist as numerous cellular proteins and proteins are NOT stored as body fuel source

True

•C H O primarily stored in liver and skeletal muscles-total mass of C H O stores is relatively small (approximately 500 grams of 1 pound)

True

White adipocytes sites

Epicardial, mesenteric, subcutaneous

Low energy diets results in loss of both what

fat and fat free mass

Whats not the goal of losing mass and why

Lean mass

skeletal muscle mass=loss of strength

lean mass is for resting energy, loss of fat-free mass results in decreases in resting metabolic rates

Loss of organ mass can result in reduced function

Resting metabolic rate decreases during diet-induced weight loss

True

•A bout of exercise increases energy expenditure and metabolic rate can remain elevated for several hours post-exercise

True

increases muscle protein synthesis and preserves muscle mass during low energy dieting

Resistance training

Five steps to achieving a healthy %body fat

•Measure your body composition

•Determine if your current percent body fat exceeds the healthy range (if not, compute weight loss required to reach healthy range)

•Establish your daily total energy expenditure

•Compute the caloric deficit needed to achieve your desired body weight

•Using information gained in steps 1 to 4, formulate your plan to lose the desired weight

Goal weight=

fat-free weight ÷ (1 − goal % fat) where goal %fat is expressed as a fraction (0.20

Fat-free weight equation using 162 pounds, body fat 36$ with a goal of 20% body fat off

100% − 36% fat = 64% fat-free

64% × 162 lbs = 103.7 lbs fat-free weight

Resting energy expenditure

Men: R E E (kcal) = (10 × weight) + (6.25 × height) − (5 × age) +5

Women: R E E (kcal) = (10 × weight) + (6.25 × height) − (5 × age) − 161

Note: weight is in kilograms; height is in centimeters; age is in years

Daily total energy expenditure

Typically estimated to be 10% of your R E E + P A/E

•For example if your R E E + P A/E is 1800 kcal/day, your T E F would be:

•0.10 × 1800 kcal = 180 kcal

Calculations of PA/E exergy expenditure

•Sedentary (little or no exercise, desk job) = 0.15 × R E E

•Light activity (light exercise/sports on 1 to 3 days/week) = 0.20 × R E E

•Moderate activity (moderate exercise/sports on 3 to 5 days/week) = 0.25 to 0.30 × R E E

•High activity (intense exercise/sports on 6 to 7 days/week) = 0.35 to 0.45 × R E E

How to achieve a healthy percent body fat

•Many successful weight-loss programs include both a reduction in caloric intake and increased caloric expenditure via exercise

•CDC recommends a max caloric reduction of 500 to 1000 kcal/day

•ACSM guidelines for exercise weight loss: resistance training 3 days week along with endurance exercise training most days of week (150 to 300 minutes/week of endurance exercise)