Body Composition

most methods consider body having two components:– fat component, i.e. fat mass– fat-free component, i.e. fat-free mass (FFM)

body fat % is the % of total body weight– average values: women, ~25%; men ~15%– minimal values: women, 8-12%; men – 5%– considered obese: women, >30%; men >20%

essential and non-essential fat

Reference body composition components for men and women

Ratings of % Fat (ages 20-29 yr)

Rating Men Women

Excellent 6-9 10-17 Good 10-14 17-21 Acceptable 15-19 21-25 Too Fat 20-22 27-32 Obese >22 >32

Determining Ideal Body Weight

Indirect approaches Metropolitan height–weight tables body mass index (BMI)

– weight (kg) / height2 (m2)– ideal range is 18-25– >30 considered obese

Direct approaches hydrostatic (underwater) weighing anthropometric (skin-fold) measurements bioelectrical impedance analysis (BIA)

Dr. Kolkhorst Dr. Buono

Kolkhorst Buono

Hydrostatic (Underwater) Weighing

determines body density principles involved:

– fat is less dense than water– FFM is more dense than water

assumptions:– fat density is 0.9007 g/cm3

– FFM density is 1.1000 g/cm3

SE = 2.5 - 3.0 % accuracy influenced by sex, age, race,

muscle mass, RV determination

Anthropometric (Skinfold) Measurements

>100 equations available from which to choose

most commonly used–and most accurate–are generalized equations by Jackson et al.

SE = 3.5 - 4.0% accuracy affected by extremes in age, % fat,

race

Bioelectrical Impedance

dual-energy X-Ray absorpitometry (DXA)– Perhaps most accurate

method

air-displacement plethysmography (BOD POD)– measures change in BOD

POD volume and subject’s weight

Suggested Reading on Body Composition

Houtkooper, L.B. and S. Going. Body Composition: How should it be measured? Does it affect sport performance? 7(5), SSE#52, 1994. http://www.gssiweb.com

Body Composition and Sport Performance

clear relationship between low % fat and better performance

Question: What is ideal % fat? potential consequences of large weight loss:

– chronic fatigue– Female Athlete Triad

ACSM Position Stand papers

Nutrition and athletic performance – http://www.acsm-msse.org/pt/pt-core/template-jour

nal/msse/media/1200.pdf

Weight loss strategies – http://www.acsm-msse.org/pt/pt-core/template-jour

nal/msse/media/1201.pdf

You measure a 21-year old man to have 18.2% body fat.

A. He should lose some body fat.

B. He is at an ideal weight.

C. He is underweight.

A subject who weighed 200 lb was estimated from an underwater weighing test to be 20% fat.

What is his fat-free mass?

A. 20 lb

B. 120 lb

C. 160 lb

D. 180 lb

E. 200 lb

F. cannot be determined

Weight Management

Weight change = energy intake – energy expenditure

Energy Intake caloric density

– CHO = 4 kcal/g– protein = 4 kcal/g– fat = 9 kcal/g– ethanol = 7 kcal/g

influence of diet composition

Your girl/boy-friend gives you part of her/his Snicker’s candy bar. It contains 6 g of fat and there is 100 kcal of energy. What is the percentage of energy that comes from fat?

a. 6 kcal

b. 600 kcal

c. 6%

d. 54%

e. 60%

f. cannot be determined

Snicker’s bar contains 6 g of fat and has 100 kcal of energy– fat has 9 kcal of energy per g – 6 g 9 kcal/g = 54 kcal from fat– 54 kcal (fat) / 100 kcal (total) = 54%

Weight ManagementCalculate % Intake from Fat

Breakfast - McDonald's Energy(kcal)

Fat(g)

Sausage McMuffin w/Egg 517 331% Milk - 8 oz 110 2Hash Brown Potatoes 125 7

Lunch - Burger King Bacon Double Cheeseburger 510 31French Fries - regular 227 13Chocolate Shake - 10 oz 374 11

Snack Snicker's Candy Bar 280 13

Dinner - Taco Bell Two Tacos 372 16Combination Burrito 404 16Pepsi - 24 oz 288 0

TOTAL (40% of intake from fat) 3,207 142

Weight Management

Energy Expenditure basal metabolic rate (BMR) affected by:

– energy intake– exercise

activity / exercise

Weight ManagementEnergy Expenditure (kcal/min)

Activity 123 lb 183 lb basketball 7.3 11.5Circuit training 9.8 15.4Cycling (9.4 mph) 5.6 8.3Running (9 min/mile) 10.8 16.0Running (7 min/mile) 13.3 18.5Swimming (slow) 7.2 10.6Swimming (fast) 8.7 12.9Tennis (singles) 6.1 9.0Walking (3.0 mph) 4.5 6.6Sitting (quietly) 1.2 1.7

Effects of low-energy intake on

RMR

Bray, Lancet, 1969

Effects of low-energy intake and exercise on RMR

Effect of energy intake on RMR

Female Athlete Triad

female athletes most prone to

eating disorders, affects 30-65%

R = regular mensesO = oligomenorrheaA = amenorrhea

Relationship between vertebral bone mineral density (BMD) and menstrual history

Suggested Reading on Female Athlete Triad

The Female-Athlete Triad. 8(1), RT# 27, 1997. [Roundtable Discussion] http://www.gssiweb.com

A very low-energy diet would likely ____ the resting metabolic rate.

a. increase

b. decrease

c. have no effect on

Young female athletes who are not menstruating or have irregular menstruation,

a. may not be consuming enough energy.

b. are at increased risk of osteoporosis.

c. both of the above are correct