What Is a Healthy BMI for Women Over 40?

The standard BMI chart was built from data on younger populations. For women in their 40s, 50s, and beyond, the thresholds carry important nuances that most guides ignore.

Body Mass Index was developed by Belgian mathematician Adolphe Quetelet in the 1830s and adopted by the medical community as a population-level screening tool in the 1970s. Its primary virtue is simplicity — one number from two measurements — and its primary limitation is that it was never designed to capture what happens to a woman's body as it moves through perimenopause and menopause. For adults of all ages, the standard BMI categories are: below 18.5 underweight, 18.5 to 24.9 normal weight, 25 to 29.9 overweight, and 30 or above obese. These cutoffs were established from population studies predominantly composed of younger adults.

The evidence for their validity in postmenopausal women is more mixed than most clinicians acknowledge. A 2014 meta-analysis published in Obesity Reviews examined data from over 113,000 postmenopausal women and found that the BMI-to-mortality relationship did shift — women with BMI between 25 and 27 had lower mortality risk than those between 18.5 and 23, contradicting the assumption that a BMI below 25 is always optimal after age 50. The analysis suggested that slightly higher BMI ranges in older women may reflect protective lean mass reserves that become increasingly important as the body ages. A separate 2020 study in JAMA Network Open on 52,000 women found that the lowest mortality risk in women aged 55 to 64 was associated with BMI between 24.5 and 27.9. This does not mean that obesity becomes healthy with age.

Visceral fat — the kind that accumulates around the organs in the abdomen — remains metabolically damaging at any age. A 2019 study in PLOS ONE tracking 156,000 postmenopausal women found that waist circumference was a stronger predictor of cardiovascular mortality than BMI alone. The key insight for women over 40 is that BMI is one signal, not the whole picture — and that the optimal range for health outcomes shifts slightly upward with age while the danger of abdominal fat remains constant. Waist circumference adds critical information: a measurement above 35 inches in women correlates with elevated visceral fat regardless of BMI.

Combining BMI with waist measurement and physical activity level gives women over 40 a much more actionable picture than a single number from a BMI chart.