For a woman measuring 1.70m, the body mass considered normal by the World Health Organization corresponds to a BMI between 18.5 and 25. Translated into kilograms, this gives a fairly wide range. However, this range does not say much about the actual health status, as it ignores body composition, age, and each person’s medical history.
Body fat and muscle mass: what weight on the scale does not measure
Two women of 1.70m can display the same weight and have very different body profiles. One practices weight training several times a week, while the other is sedentary. Their kilograms are distributed differently between bones, muscles, water, and fat tissue.
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The current debate in nutrition and sports medicine emphasizes body composition rather than the simple number displayed on the scale. A body fat percentage between 25 and 30% is generally considered normal and healthy for an adult woman, according to the benchmarks used in clinical practice.
In concrete terms, a woman of 1.70m weighing 68 kg with developed muscle mass does not have the same metabolic risk as a woman of the same height and weight whose fat mass is high. This is why focusing on a single number of normal weight for a woman of 1.70m without considering this distribution gives an incomplete picture.
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BMI for a woman of 1.70m: calculation and concrete limits
The body mass index is calculated by dividing weight in kilograms by height in meters squared. For 1.70m, the formula is: weight divided by 2.89. The WHO classifies the result into categories.
- Below 18.5: underweight, associated with nutritional and hormonal risks.
- Between 18.5 and 25: normal weight, reference range for the adult population aged 18 to 65.
- Between 25 and 30: overweight, increased risk factor for certain cardiovascular and metabolic pathologies.
- Above 30: obesity, with specific thresholds for medical management.
For a height of 1.70m, the weight range corresponding to a normal BMI extends from about 53 kg to about 72 kg. The gap of almost 20 kg between these two limits shows how vague the notion of “ideal weight” remains when relying solely on BMI.
Why BMI is not enough as a health indicator
BMI was designed as a statistical tool for populations, not as an individual diagnosis. It does not distinguish between fat mass and muscle mass. An athletic woman with a BMI of 26 may be in better metabolic health than a sedentary woman with a BMI of 23.
For women over 65, the benchmarks change: a normal BMI is more likely between 21 and 25, as too low a weight increases the risk of bone fragility and sarcopenia. Age thus modifies the interpretation of the same number.
Formulas for calculating ideal weight: what they are really worth
Several formulas circulate to estimate a reference weight. They yield different results, sometimes by several kilograms, for the same height.
The Lorentz formula, often cited, incorporates height but not age or body type. The Creff formula adds a coefficient related to bone structure (fine, medium, large). The Devine formula, derived from pharmacology, was designed to calculate medication dosages, not to define a weight goal.
None of these formulas have diagnostic value. They produce an order of magnitude, not a target to achieve. Their main flaw is the same as that of BMI: they ignore body composition and individual medical context.
Medical management of weight: the thresholds that matter in 2026
The French medical framework has recently evolved. Since June 2026, health insurance reimburses certain anti-obesity treatments, but only for adults with a BMI of 40 or higher, or a BMI of 35 or higher with at least one associated comorbidity. The additional condition: having undergone at least six months of nutritional management without sufficient results.
The first prescription for these reimbursed treatments is reserved for specialist doctors, not the general practitioner. This structured care pathway shows that weight management has shifted towards a comprehensive risk assessment, far beyond simply reading a number on the scale.
When to consult a doctor about weight
The question of weight deserves medical advice in several specific situations:
- Rapid and unexplained weight gain or loss over a few months.
- High waist circumference, even with a normal BMI, as abdominal fat is an independent cardiovascular risk marker.
- Chronic fatigue, menstrual cycle disorders, or joint pain associated with weight variation.
- Family history of diabetes or cardiovascular diseases.
A doctor can prescribe a body composition analysis (bioelectrical impedance) or a metabolic assessment to refine the evaluation, something no online formula can replace.
Weight and health: moving beyond the logic of a single number
The recent editorial and medical trend treats weight as a public health issue, not just an aesthetic one. The ideal weight is the one that allows living without metabolic constraints, with a regular diet and appropriate physical activity, over the long term.
For a woman of 1.70m, the statistically normal weight range is wide. The important number is the one where biological markers (blood sugar, cholesterol, blood pressure) remain within normal limits, where daily energy is stable, and where the body does not show warning signals. This weight can be at 58 kg or 70 kg depending on body type and level of physical activity.
Seeking a precise and universal ideal weight number for a given height remains a dead end. The most reliable assessment crosses BMI, body composition, metabolic assessment, and personal medical history, four dimensions that a doctor or dietitian is best placed to articulate.