Body fat percentage measures the proportion of your weight that's fat mass. Unlike BMI, it distinguishes between fat and muscle — making it a far more precise indicator of health and fitness. Two people with identical BMIs can have completely different body compositions and very different health risks.
Healthy Body Fat Ranges (ACE Guidelines)
CategoryMenWomen
Essential fat2–5%10–13%
Athletic6–13%14–20%
Fitness ✓14–17%21–24%
Acceptable ✓18–24%25–31%
Obese25%+32%+
How Body Fat Changes with Age
Fat naturally increases with age even at stable body weight, because muscle mass (lean mass) declines from ~30 onwards. Acceptable thresholds shift accordingly:
Age GroupHealthy (Men)Healthy (Women)
20–398–20%21–33%
40–5911–22%23–35%
60+13–25%24–36%
Measurement Methods
- DEXA scan: Gold standard. Accurate to within 1–2%. Available at gyms and medical facilities (£50–150).
- Hydrostatic weighing: Near gold standard — you're weighed underwater. Available at some university sports labs.
- Bioelectrical impedance (smart scales): Convenient but inconsistent — hydration, food, and time of day all affect readings.
- Skinfold calipers: Reasonably accurate (within 3–4%) when done by a trained practitioner.
- Circumference formulas: Uses neck/waist/hip measurements. Zero cost, no equipment, less accurate.
Why Women Carry More Body Fat
Women naturally carry more fat than men — driven by oestrogen, which promotes fat storage for reproductive health. Essential fat for women (10–13%) is more than double that for men (2–5%). Going below this threshold disrupts hormonal function, bone density, and fertility.