Ideal weight for height and age: how to assess it

The query 'my ideal weight' usually means one thing: a person needs a number to live with peacefully. More accurately, one should speak not of a single number but of a range of body weight associated with a lower risk of disease, and it is assessed by several parameters at once.

What is ideal weight and does a single number exist

Body weight is the sum of muscles, bones, fat, and water, and one indicator does not fully describe it. Medical reference books use categories: underweight, normal, overweight, obesity. Many height-weight formulas have been proposed, and each gives its own 'ideal' value:

• Broca's index — for height 155–170 cm: weight = (height in cm − 100) ± 10%;
• Breitman's index: height in cm × 0.7 − 50 kg;
• Noorden's index: height in cm × 0.42;
• Taton's index: height in cm − (100 + (height in cm − 100) / 20).

For a height of 170 cm, these formulas give 70, 69, 71.4, and 66.5 kg respectively. Four numbers, four different 'ideals' — and none takes into account the individual's body build.

How ideal weight relates to height and BMI

Body mass index (BMI) is the ratio of weight in kilograms to the square of height in meters, unit kg/m². The formula was proposed by Adolphe Quetelet in 1835. Example: 77 kg at a height of 170 cm gives a BMI of about 26.64 kg/m². According to WHO criteria for adults, a BMI of 25–29.9 is overweight, 30 and above is obesity. For people of South Asian, Chinese, other Asian, Middle Eastern, African, and African-Caribbean origin, the thresholds are lower: 23–27.4 and 27.5 and above.

The second reference point is waist circumference: it should be kept less than half of height. The waist-to-height ratio calculator can be used if BMI is below 35. Fat in the abdominal area is associated with a higher risk of heart disease and type 2 diabetes.

Weight at heights of 160 and 165 cm: how to read the reference points

At a height of 160 cm, Broca's index gives 54–66 kg, at 165 cm — 58.5–71.5 kg. The BMI threshold of 25 corresponds to 64 kg at 160 cm and 68.1 kg at 165 cm; the threshold of 30 — 76.8 and 81.7 kg. Waist by the 'less than half of height' rule — up to 80 and up to 82.5 cm. These are starting points for discussing risks, not a goal to which the body should be adjusted.

How age affects body weight assessment

The interpretation of BMI recommended by WHO does not take sex and age into account. Statistics show that BMI is higher in men than in women, and in mature adults than in young and elderly people. In the elderly, preservation of muscle and strength becomes key, and BMI in a person who has lost muscle mass may underestimate the proportion of fat. Sudden weight loss without intention at any age requires investigation: among its causes are thyroid diseases, oncological, infectious, and digestive diseases, and the use of certain medications. Sudden weight gain is associated, in particular, with medications, thyroid diseases, heart failure, kidney and liver diseases.

Limitations of BMI and ideal weight formulas

BMI does not distinguish fat, muscle, and bone mass: in people with developed musculature it overestimates the proportion of fat, in the elderly and those who have lost muscle — it underestimates. In a sample of Finnish residents with a BMI below 25, at least 20% of men and at least 30% of women had elevated fat content. The boundaries of normal have changed: until 1998 in the USA, a BMI up to 27.8 kg/m² was considered normal, then the upper limit was lowered to 25, and in Hong Kong and Japan obesity is considered from 25. Broca's index is applicable only to height 155–170 cm. The relationship between life expectancy and BMI is described by a J-shaped curve with a maximum around 25–27 kg/m². The formulas are based on population data, so for an individual they remain an approximate estimate — roughly like the average temperature in a hospital, only with units of measurement.

When to discuss weight with a doctor

One should consult a doctor if BMI falls into the category of overweight or obesity and the person wants to lose weight, waist is more than half of height, there is prediabetes, diabetes, high blood pressure, joint pain, high cholesterol, sleep apnea, or cardiovascular diseases, a family history of obesity, or an eating disorder. The doctor assesses BMI, waist circumference, and health history, and if necessary refers to a dietitian. Overweight increases the risk of type 2 diabetes, heart disease, stroke, hypertension, certain cancers, osteoarthritis, and fatty liver disease; even a weight loss of 5–10% improves health.

The number on the scale alone is not a reason to call an ambulance; 103/112 — for signs of stroke or heart attack and other life-threatening conditions.

The numbers above are not a nutritional recommendation or a diagnosis, but a reason for calculation and a conversation with a doctor; the material is for reference and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer