You step on the scale, calculate your BMI, and the number falls within the so-called “normal” range. This result is not enough to provide a reliable assessment. A woman’s BMI tells part of the story, but it overlooks the actual body composition, fat distribution, and the influence of age on the figure.
Why waist circumference complements BMI better in women
The BMI formula divides weight by height squared. It does not distinguish between a kilo of muscle and a kilo of fat. For women, this limitation poses a real problem: abdominal fat, even with a normal BMI, increases cardiovascular risk.
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An analysis from the Nurses’ Health Study II cohort showed that waist circumference predicts cardiovascular risk better than BMI alone, even among women whose scores fall between 18.5 and 24.9. Two women with the same BMI can have radically different health profiles depending on where their fat mass is located.
In practical terms, a woman with a BMI of 23 and little visceral fat does not have the same prognosis as a woman with the same BMI whose fat is concentrated around the abdomen. The number on the scale is not enough to assess female body composition on Hub Santé, which is why health professionals are increasingly measuring waist circumference as a complement.
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BMI in women after menopause: guidelines change with age
Have you ever noticed that weight recommendations seem fixed, as if the body doesn’t change between the ages of 30 and 65? The physiological reality is quite different.
With age, muscle mass naturally decreases. This phenomenon, known as sarcopenia, means that a BMI identical at 35 and 65 years does not correspond to the same body composition. For a 65-year-old woman, a BMI of 20 may mask significant muscle loss.
Since 2022, the European Association for the Study of Obesity (EASO) has recommended considering a slightly higher BMI as compatible with good health after 60, provided there are no comorbidities or excessive abdominal fat. This position is based on an observation: a slight weight reserve plays a protective role in older women, particularly against fractures and infections.
What this changes in practice
For a woman over 60, aiming for a BMI of 21 or 22 at all costs may not have medical sense. Maintaining muscle mass, through physical activity and adequate protein intake, matters more than the number displayed by the formula.
Harmonious silhouette and BMI: the gap between perception and health
A survey conducted in France (Péron J. et al., published in La Presse Médicale) highlighted a striking gap. Many women consider their silhouette “too round” with a BMI of 22 or 23, while the physicians surveyed view this same BMI as healthy and aesthetically harmonious.
This gap is not trivial. It drives some women toward restrictive diets to achieve a BMI below 20, risking muscle loss and weakening their bone density. The pursuit of a “slimmer” silhouette can then produce the opposite effect on health.
What complementary indicators reveal
Rather than relying solely on BMI, several indicators provide a more accurate picture of health and silhouette:
- Waist circumference: it directly reflects visceral fat, which surrounds the organs and increases metabolic risks
- Body fat percentage: measured by bioelectrical impedance or skinfolds, it distinguishes fat from muscle, where BMI remains blind
- The waist-to-hip ratio: it specifies fat distribution between the upper and lower body, a recognized cardiovascular risk factor
These measurements do not replace BMI, but they complement it. A BMI of 24 with a low body fat percentage and a correct waist circumference often indicates a toned silhouette and good health.
Muscle mass and physical activity: the real lever for the female silhouette
Physical activity alters body composition without necessarily changing BMI. A woman who engages in weight training or muscle strengthening may see her weight plateau or even increase slightly while refining her silhouette.
Muscle is denser than fat: at equal volume, it weighs more. This is why two women with the same BMI can have very different silhouettes depending on their level of physical activity.
To preserve or develop muscle mass, a few concrete levers make a difference:
- Engage in muscle strengthening at least twice a week, even with bodyweight exercises
- Maintain an adequate protein intake, spread throughout the meals of the day
- Avoid dropping too low in calories: very restrictive diets accelerate muscle loss and slow down metabolism
The goal is not to aim for a precise number on the scale, but to build a functional, toned, and healthy body. BMI provides a starting indication, to be cross-referenced with other measures for informed decisions.
A BMI between 18.5 and 24.9 corresponds to the range considered normal by the WHO. In women, this number benefits from being read alongside waist circumference, body fat percentage, and level of physical activity. After 60, a slightly higher BMI does not equate to poor health. The most harmonious silhouette is one that reflects a balance between muscle mass, appropriate nutrition, and regular movement.