7_Body Composition
Body Composition Overview
Body composition assesses the distribution of fat and fat-free mass in the body, which can influence health and athletic performance.
Regional body fat percentages and overall health risks vary across different populations and age groups.
Page 1: Introduction to Body Composition
Body composition percentages by region:
Yukon: 23.2%
Northwest Territories: 21.5%
Nunavut: 24.5%
British Columbia: 20.0%
Alberta: 25.1%
Manitoba: 20.4%
The document originates from "Exercise Physiology For Health, Fitness, and Performance" by Denise L. Smith, Sharon A. Plowman, Michael J. Ormsbee.
Page 2: Learning Objectives
Understand the importance and types of body composition.
Explore various methods for measuring body composition.
Discuss the connection between body composition, health, and obesity.
Examine fat cell metabolism and its impact on metabolic health.
Page 3: Body Composition in Athletic Performance
Body size and shape are vital for athletic performance;
Strength/power athletes may have higher fat mass.
Athletes with weight classes benefit from a better power/weight ratio.
Acrobatic sports leverage biomechanical advantage.
Judged sports favor increased fat-free mass with reduced body fat.
Body composition can be manipulated for performance enhancement.
Page 4: Important Considerations
Body composition should not be viewed as the sole indicator of athletic potential.
Rigid body composition standards can be detrimental:
Athletes need a healthy balance of leanness and power.
Example quotes:
Judy Goss emphasizes the flexibility needed in body weight recommendations.
Rosie Maclennan emphasizes performance over aesthetics in sports.
Page 5: Components of Body Composition
Body mass is partitioned into fat-free mass and fat mass:
Fat-free mass: includes muscle, bones, organs, skin, and blood.
Fat mass: includes essential fat (3-5% for males, 8-12% for females) and storage fat (subcutaneous and visceral).
Terms to know:
Lean body mass: fat-free mass + essential fat.
Page 6: Methods of Measuring Body Composition
Various methods for body composition assessment:
Anatomical (cadaver analysis).
Chemical analysis (fat vs fat-free components).
Physical dissection analysis (fat, adipose tissue, muscle).
Measurement techniques:
BMI, circumferences, skinfolds.
Bioelectrical impedance analysis (BIA).
Densitometry (hydrostatic weight, displacement plethysmography, Bod Pod).
Dual energy x-ray absorptiometry (DXA).
CT and MRI scans.
Page 7: Body Mass Index (BMI)
BMI defined as total body weight in relation to height:
Example: Weight - 200 lbs, Height - 5’8” results in a BMI of 30 (Class 1).
Limitations of BMI:
Poor predictor of body fat percentage; various factors affect results (age, ethnicity).
Lack of detail on fat distribution.
Page 8: Waist/Hip Ratio and Circumferences
Waist/hip ratio is a predictor of metabolic disease risk:
High-risk thresholds by age:
Ages 20-60: >0.84 (female), >0.99 (male).
Ages 60-70: >0.90 (female), >1.03 (male).
Circumference measurements:
Females: risk at >88 cm (35 inches).
Males: risk at >102 cm (40 inches).
Page 9: Skinfold Measurements
Skinfold thickness assessed using calipers at particular sites.
Common issues leading to errors: landmarking, measurement techniques.
Skilled testers achieve accuracy within 3-5% relative to hydrostatic weighing.
Requires population-specific equations for calculating body density.
Page 10: Bioelectrical Impedance Analysis (BIA)
Utilizes low-intensity electrical current to differentiate between lean body mass and fat mass:
Lean tissue conducts current; fat tissue does not.
Method has significant error margins due to hydration levels affecting results.
Page 11: Densitometry and Hydrostatic Weighing
Densitometry measures mass per unit volume:
Hydrostatic weighing uses fat and fat-free mass in calculations (fat = 0.9 g/ml; lean = 1.1 g/ml).
Improves estimates of body fat percentage.
Page 12: Bod Pod
Air displacement system to assess body volume and density:
Determines body fat percentage using a predictive formula.
Provides high accuracy, with a potential 2-3% underestimation of body fat.
Page 13: Error Sources in Densitometry
Factors affecting densitometry measurements include:
Residual volume, GI volume, protocol errors, and individual density variations.
Body fat percentages assessed may vary by +/- 2-4%.
Page 14: Dual Energy X-ray Absorptiometry (DXA)
Measures:
Lean tissue, fat mass, and bone density in a three-compartment model.
Offers a comprehensive body composition assessment with the least error margin.
Page 15: Healthy Body Fat Percentages
No universal standard for body fat percentage:
Obesity defined as being 5% above normal.
Guided values:
Females: 25-35% (essential 8-12%).
Males: 8-25% (essential 3-5%).
Page 16: Changes in Adipose Cells in Obesity
Total fat cell count varies significantly by gender (30-50 billion in females).
Hyperplasia: Increase in number of fat cells during critical growth phases.
Hypertrophy: Enlarging of existing fat cells to store fat efficiently.
Page 17: Fat Cell Metabolism
Role of lipoprotein lipase (LPL) in fat storage:
Women store fat in breasts, hips, and thighs due to higher LPL activity.
Men's abdominal fat cells show different LPL patterns.
Gender differences affect fat distribution patterns.
Page 18: Influence of Physical Activity on Metabolic Health
Overweight does not directly correlate to poor metabolic health;
Increased physical activity improves health outcomes regardless of weight.
Emphasizing fitness over body aesthetics is crucial.
Page 19: Review Questions
Key questions for reflection:
Difference between fat weight and fat-free weight in genders.
Evaluation of body composition measurement effectiveness.
Development of adipose cells from childhood to adulthood.
Advantages and challenges of focusing on body composition for athletic performance.