Why BMI is less accurate for women
Two biological factors make BMI particularly imprecise for women. First, women naturally carry a higher percentage of body fat at the same BMI as men — approximately 10–12 percentage points higher at a given BMI. A woman with a BMI of 22 may have a body fat percentage of 26–30%, while a man at the same BMI typically carries 14–18%. This means the health implications of the same BMI category differ substantially between sexes, and the current WHO thresholds were developed primarily from male reference populations.
Second, hormonal changes across the life course — particularly the oestrogen decline at menopause — drive fat redistribution toward the abdomen, increasing metabolic risk even without any change in BMI. A postmenopausal woman who maintains the same BMI she had at 35 may have substantially more visceral fat at 55. Waist circumference becomes an increasingly important complementary measurement after menopause.