Body composition

The ratio of fat, muscle and other tissues

Body composition is what makes up your weight: fat mass and lean mass (muscle, bone, water, organs).

Why this matters more than the number on the scale and BMI: two people of the same weight can have completely different health — one because of muscle, the other because of fat. Body composition shows the quality of weight, not just its quantity.

Reference ranges

Approximate healthy ranges for the fat share (the rest is lean mass):

Men — normal	10 – 20% fat
Women — normal	18 – 28% fat
Obesity (by fat)	men > 25%, women > 32%
Lean mass	muscle, bone, water, organs

Important: The exact limits depend on age, sex and the measurement method. What matters more than a single figure is the trend: whether muscle or fat mass is growing.

What an elevated level means

A "high" unfavorable body composition is an excess of fat mass, especially visceral fat around the organs. It is linked to insulin resistance, hypertension and cardiovascular risk — even at a normal weight ("hidden obesity").

What a low level means

The opposite variant is also unfavorable — a deficit of lean (muscle) mass. Little muscle with normal or excess fat is sarcopenia (or sarcopenic obesity): strength and metabolism are reduced, and the risk of falls and disease grows.

Too low a fat mass is also harmful: hormones, bones and reproductive function suffer.

How the test is done

Body composition is assessed by bioimpedance (smart scales, analyzers), skinfold calipers, and more accurately — DEXA. Home methods give a rough guide, accurate ones — a reference.

What matters is not a one-off figure but the trend: the goal of a healthy change in the body is to lose fat while keeping or building muscle, not simply to "lose weight".

What affects the value

Strength training and protein — increase muscle mass.
A calorie deficit — reduces fat (and the risk of losing muscle).
Age — over the years muscle is lost and fat accumulates.
Hormones and sleep — affect the fat/muscle balance.
The measurement method and hydration — affect the bioimpedance result.
Sex — in women the fat share is physiologically higher.

Assess body composition

Assess the ratio of fat to muscle from available measurements:

Body Composition Body fat, muscle mass (FFMI, SMM, SMI), body shape, and ABSI — all in one Open Body Fat Your body fat percentage and the norms for your sex and age Open

Frequently asked questions

Why is body composition better than BMI?

BMI takes into account only weight and height and does not distinguish fat from muscle. A muscular person may have an "excess" BMI while being healthy, and a person with a normal BMI may have hidden obesity. Body composition shows the real ratio of fat to muscle.

What fat percentage is considered healthy?

Roughly 10–20% in men and 18–28% in women; the exact limits depend on age and method. Too high a fat share is harmful, but so is too low — it disrupts the hormonal balance and bone health.

Can smart scales be trusted?

Bioimpedance scales give a rough guide and show the trend well, but they are sensitive to hydration and time of day. For an accurate assessment DEXA is used. Measure under the same conditions and follow the trend, not a single figure.

Sources

info

This content is educational and does not replace consultation with a physician. Reference ranges may vary depending on the laboratory and method — rely on the ranges stated on your own test report.

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