Body Composition Metrics — Body Fat, Lean Mass, Weight, and Sarcopenia
Body Composition Metrics — Body Fat, Lean Mass, Weight, and Sarcopenia
What Is Body Composition?
Body composition describes what your body is physically made up of: bone, fat, and lean mass (muscle). Styku's body composition algorithm is scientifically validated and is generally within 1–2% of the gold standard Dual-Energy X-ray Absorptiometry (DXA) scanner.
Improvements in body composition consist of:
- Lowering body fat percentage
- Gaining lean mass
📄 Peer-reviewed validation paper (correlation of 0.95+ with DEXA for fat mass): Styku Phoenix Validation Paper
Body Fat Percentage
Body fat percentage is the proportion of your total body weight that is fat. For example, a body fat percentage of 34% means 34% of your body weight is fat.
- Styku's algorithm is generally within 1–2% of a DXA scanner.
- Fat serves important functions: energy reserve, organ cushioning, insulation, and temperature regulation.
- Excess fat — particularly abdominal fat — increases chronic disease risk and can negatively impact mobility and physical function.
Body Fat Risk Categories
Males:
Body Fat % | Category
< 5% | Low Body Fat Risk
5–7.9% | Essential Fat
8–11.9% | Athlete
12–20.9% | Fit
21–27.9% | Average
≥ 28% | At Risk
Females:
Body Fat % | Category
< 12% | Low Body Fat Risk
12–15.9% | Essential Fat
16–22.9% | Athlete
23–34.9% | Fit
35–39.9% | Average
≥ 40% | At Risk
References
- Bennett JP et al. (2022). Assessment of clinical measures of total and regional body composition from a commercial 3D optical body scanner. Clinical Nutrition, 41(1), 211–218.
- Bennett JP et al. (2022). Three-dimensional optical body shape and features improve prediction of metabolic disease risk. Obesity, 30(8), 1589–1598.
- Lavie CJ et al. (2012). Body composition and survival in stable coronary heart disease. Journal of the American College of Cardiology, 60(15), 1374–1380.
- Okorodudu, D. O. et al. (2010). Diagnostic performance of BMI to identify obesity. International Journal of Obesity, 34(5), 791–799.
Body Weight and Ideal Body Weight
Body weight is the total weight of everything the body is composed of. Weight can be gained or lost through changes in muscle mass and/or fat mass.
Ideal body weight is calculated based on a targeted BMI range of 18.5 to 24.9.
Reference
- Peterson, C. M. et al. (2016). Universal equation for estimating ideal body weight and body weight at any BMI. The American Journal of Clinical Nutrition, 103(5), 1197–1203.
Sarcopenia
Sarcopenia is the age-related loss of muscle mass and function, leading to weakness and increased risk of falls and fractures. It is assessed by measuring Appendicular Lean Soft Tissue (ALST) — the muscle mass in your arms and legs — adjusted for height, expressed as the Appendicular Lean Soft Tissue Index (ALSTI = ALST / height²).
Sarcopenia Risk Categories
Category
At Risk
Not At Risk
Sarcopenia Diagnostic Cut-Off Values
Sex | ALST Threshold
Men | < 7.0 kg/m²
Women | < 5.5 kg/m²