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Body Composition

Measurement TechniquesMeasurement Techniques

Body Mass Index (BMI)BMI = Body Mass (kg) / Stature (m2)

Figure 28.1

Body Mass Index (BMI)BMI = Body Mass (kg) / Stature (m2)

Figure 28.1

Obesity Standards

BMI BMI ≥≥ 3030

BMI LimitationsFails to consider fat distribution

Factors other than excess fat• Bone• Muscle mass• Increased plasma volume with training

Sport specific body composition factors

Composition of the Human BodyVarious component models

Major structural components include muscle muscle massmass, fat massfat mass, and bone massbone mass

Most studies divide body into:• Fat-free mass (FFM)• Fat mass (FM)

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Reference Male

Figure 28.5

Reference Female

Figure 28.5

Composition of the Human Body (cont.)

Underweight and thin• Terms are not always synonymous• Essential and storage fat

Leanness, regular exercise, and menstrual irregularity• Lean:fat ratio

Delayed onset of menstruation and cancer risk• Females require body fat to maintain menstruation

Assessing Body CompositionDirect assessment• Analysis of cadaver

Indirect assessment1. Hydrostatic weighing2. Bod Pod3. Skinfold and girth measurements4. Surface anthropometry5. Bioelectrical impedance analysis (BIA)6. Magnetic resonance imaging7. Dual-energy X-ray absorptiometry

Hydrostatic WeighingBody volume measurement• Water displacement

Calculating body composition from• Body mass• Body volume • Residual lung volume

Assumptions• Density of FM and FFM

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Bod PodAir displacement vs. H2O (Hydrostatic weighing)

Skinfold and girth measurementsSubcutaneous fat measurement• Caliper• Measurement sites

Usefulness of skinfold scores• Consistent & meaningful scores

Skinfolds and age• More fat deposits internally as one ages

Girth MeasurementsUsefulness of girth scores• Helps rank individuals• Practical value – clothing

Body fat predictions from girths• Requires 5 steps• Not as common as other

techniques

Surface anthropometryThe body profile (matrix of 11 girths)

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Bioelectrical impedance analysis (BIA)Influence of hydration level • Dehydration will increase score

Influence of ambient temperature• Warm air causes more sweat• Wet skin results in lower scores

Applicability of BIA in sports and exercise training• Not as good a predictor as skinfolds or girths

MRI Dual-energy X-ray absorptiometryDEXA

Body Composition

Physique, Performance, & Physique, Performance, & Physical ActivityPhysical Activity

Individual PhysiquesSomatotyping has generally been used to classify physiques• Endomorph (fat)• Ectomorph (thin)• Mesomorph (muscular)

Athletes• Gender differences• Fat-free-to-fat ratio• World records

Geographic region• Genetic racial differences

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Figure 29.1 Figure 29.1

Figure 29.2Lean-to-Fat Ratio

Figure 29.2

Physiques of Athletes (cont.)

By sport category• Field event athletes

Larger mass than other athletes

• Female endurance athletesBody fat similar to non-active males

• Male endurance athletesExtremely low body fat

• TriathletesBody fat & aerobic capacity similar to other endurance athletes

Percentage Body Fat of Elite AthletesSwimmers, runners, & football players

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Wrestlers• Proposed lowest acceptable level for safe competition

Male & Female weight lifters and bodybuilders• Body fat averages less than 10% (females ~ 13%)• Body builders are larger in girth measurements

ShoulderChestBiceps & forearms

Ballet & gymnasts

Basketball

Body Composition

Overweight, Obesity, & Overweight, Obesity, & Weight ControlWeight Control

Physical Inactivity Statistics

• 97 million American adults are overweight or obese

• Nearly 15% of American children are overweight

• Healthcare costs for treating obesity (268 billion)

American Medical AssociationAmerican Medical Association• Of the 250,000 deaths/yr,

12% are related to inactivity• 28% of American adults

aren’t active at all• 38% of people 55yr and

older are sedentary

American Heart AssociationAmerican Heart Association

Physical Inactivity Statistics

Centers for Disease ControlCenters for Disease Control• Obesity at 20.9% (2001)• 44.3 million adults defined as

obese (BMI>30)• 7.9% diagnosed with diabetes

(including gestational)

Physical Inactivity Statistics ObesityVery complex and involves:1. Genetics2. Environmental factors3. Metabolic parameters4. Behavioral factors5. Social influences

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Figure 30.2

ObesityGenetics influences body fat accumulation• Mutant gene

Leptin – hormone that regulates fat metabolismLeptin normally blunts drive to eatIf defective, the signal is not received

Physical inactivity-crucial component in excessive fat accumulation

Age-Related Decreases in Activity & Increased Body Fat

Figure 30.4

Age-Related Decreases in Activity & Increased WHR

Figure 30.4

Specific health risksHypertension

Stroke

Renal Disease

Sleep apnea

Osteoporosis

Cancer – endometrial, breast, colon

Elevated plasma lipids

Gallbladder disease

Menstrual irregularities

Emotional / social / psychological problems

Criteria for excessive body fatPercentage body fat• Children = > 85th percentile• Men > 20% body fat• Women > 30% body fat

Regional fat distribution• Central or android-type obesity• Peripheral or gynoid-type obesity

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Obesity (cont.)Lipoprotein lipase affects body fat distribution• LPL plays a role in gender differences in fat

patterning• Females have greater LPL activity in hips, thighs,

buttocks• Males have higher LPL activity in abdomen

Adipocyte size and number• Hypertrophy versus hyperplasia• Cellularity differences between non-obese and obese

persons

Obesity (cont.)Adipocyte development:1. Cell size increases as age increases

2. Between ages 1 & 6, cell size triples

3. Cell number increases rapidly in the third trimester and the first year of life

4. Cell number increases during adolescence, then becomes fairly stable

Obesity (cont.)Effects of weight loss• Adipocyte size decreases, while number remains the

same

Effects of weight gain• Moderate weight gain results from increased

adipocyte size• Severe weight gain may be accompanied by an

increase in adipocyte number

Principles of Weight Control: Diet and Exercise

Energy balance-input versus output

Dieting for weight control

Weight loss improves disease risk biomarkers

Dieting fads