Overview
This lecture covered body composition, its types, measurement methods, health implications, gender differences, and guidance on holistic health assessment and disordered eating.
Body Composition Basics
- Body composition is the ratio of fat tissue to lean tissue (also called percent body fat).
- It is a more accurate marker of health than weight or BMI alone.
- Essential fat is needed for basic physiological functions (e.g., found in organs, CNS).
- Women have higher essential fat percentages due to reproductive tissues.
- Stored fat (adipose tissue) exists as visceral (around organs) or subcutaneous (under the skin).
Types and Risks of Body Fat
- Subcutaneous fat insulates and cushions the body and is found under the skin.
- Visceral fat surrounds internal organs and is linked to higher health risks (e.g., diabetes, heart disease).
- Visceral fat is more hormonally active and easier to lose than subcutaneous fat.
Gender and Fat Distribution
- Men typically accumulate more visceral fat in the abdomen (“apple-shaped”; Android obesity).
- Women typically accumulate more subcutaneous fat in the hips/thighs (“pear-shaped”; Gynecoid obesity).
- Fat distribution affects health risk and ease of fat loss.
Fat Cell Types
- White adipocytes store energy as fat.
- Brown adipose tissue (BAT) generates heat and has more mitochondria; newborns have more BAT.
- Retaining more BAT in adulthood may relate to healthier BMI.
Healthy Body Fat Ranges
- Healthy body fat: Men 3–25%, Women 12–30%.
- Essential fat and desirable fatness should be remembered for exams.
Methods of Measuring Body Composition
- Underwater weighing: measures body volume to estimate fat %; accurate but uncomfortable.
- Air displacement (BodPod): measures air displaced; quick and fairly accurate.
- DEXA: uses X-ray to measure fat, bone, and lean mass; very accurate but less accessible.
- Bioelectrical impedance analysis (BIA): estimates fat % using electrical currents; quick, cheap, but less accurate and affected by hydration.
- Calipers (skinfold): measures subcutaneous fat at various sites; fast and cheap but less accurate if not properly trained.
- Waist circumference: >35" in women or >40" in men indicates higher health risk.
Holistic Health Assessment
- Use multiple measures (anthropometrics, labs, lifestyle) for health assessment.
- A healthy weight is maintainable with good habits and healthy blood markers, not just a number.
- Over-reliance on numbers can lead to “skinny fat”—normal weight but high body fat %.
Disordered Eating Awareness
- Read the Health Connection section in the textbook on disordered eating.
- Evaluate personal eating and body image using checklist; seek help if needed.
- Self-guided programs like “Body U” are available for support.
Key Terms & Definitions
- Body Composition — ratio of fat mass to lean mass in the body.
- Essential Fat — minimum fat needed for normal physiological function.
- Adipose Tissue — body fat stored as energy (visceral and subcutaneous).
- Visceral Fat — fat surrounding organs, higher health risk.
- Subcutaneous Fat — fat under the skin, less harmful.
- Brown Adipose Tissue (BAT) — fat cells that generate heat.
- Bioelectrical Impedance Analysis (BIA) — electrical method to estimate body fat %.
- DEXA — X-ray scan measuring bone, lean, and fat mass.
Action Items / Next Steps
- Memorize healthy body fat percentage ranges for men and women.
- Review techniques for measuring body composition and their pros/cons.
- Read Health Connection section on disordered eating in your textbook.
- Use the checklist provided to self-assess eating and body image.
- Check out “Body U” program if interested in self-guided support.