BMI knows no muscle, the body fat scale swings with hydration, and the precise measurement costs 150 euros. Which method is worth what, which values are healthy and why waist circumference matters more for health than any percentage.
In short
- BMI is a population measure; for individuals waist circumference and body fat percentage are more meaningful.
- Waist under 94 centimeters for men and 80 for women is healthy, from 102 and 88 clearly risky.
- Healthy body fat ranges: men 10 to 20 percent, women 18 to 28, a little higher with age.
- The circumference method and a tape measure are more accurate than any body fat scale and cost nothing.
What BMI can and cannot do
Body mass index, weight in kilos divided by height in meters squared, is a usable measure for populations and a crude one for individuals. It does not distinguish muscle from fat: a strength athlete with 15 percent body fat has a BMI of 28 and counts as overweight, an untrained person with 32 percent fat and BMI 24 as normal. From 25 it is called overweight, from 30 obesity, but the risk depends on where the fat sits.
Waist circumference
Fat at the belly, especially the visceral fat around the organs, is metabolically active and drives inflammation, insulin resistance and blood lipids. Fat on hips and thighs is largely harmless. That is why waist circumference says more than BMI: under 94 centimeters for men and 80 for women is healthy, 94 to 102 and 80 to 88 elevated, above that clearly elevated. Measure in the morning, fasting, halfway between the lowest rib and the hip bone, exhaled and relaxed. The waist-to-height ratio is even simpler: waist should be less than half your height.
The methods
Body fat scales send a weak current through the body and estimate fat from the resistance. They swing by 3 to 5 percentage points with hydration, time of day, meals and training; usable as a trend over weeks, not as a single value. The US Navy circumference method calculates the share from neck, waist and, for women, hips, with an accuracy of 3 to 4 percent, without a device. Caliper skinfold measurement is accurate when the same trained person measures. DEXA, the bone density scan with body composition, is the gold standard with 1 to 2 percent accuracy, costs 100 to 200 euros and additionally shows visceral fat and muscle distribution.
Healthy ranges
For men 10 to 20 percent count as healthy, 20 to 25 as elevated, above that as high; for women 18 to 28 as healthy, 28 to 33 as elevated. With age the ranges shift up by about 2 to 3 points. Very low values, under 6 percent for men and 14 for women, disturb hormones and immune system. Athletic means 10 to 14 for men, 18 to 22 for women.
What is worth measuring
Once a month waist circumference and weight, both in the morning. Once a quarter the circumference method. Once a year or with major changes a DEXA scan if you want it precise. And the rule: whoever loses waist circumference while keeping strength is doing everything right, whatever the scale says.
Try it
Body Fat CalculatorHeight, weight, waist, neck and for women hips: your body fat percentage by the circumference method, BMI and fat-free mass.Calorie CalculatorHeight, weight, age, activity: your basal metabolic rate, your daily needs and the calories to lose, maintain or gain.Weight Loss PlannerCurrent weight, target weight, pace: when you arrive, how many calories that means and how to keep muscle along the way.Frequently asked questions
How accurate is my body fat scale?
To 3 to 5 percentage points, with daily swings. Always measure in the morning fasting after using the bathroom and look only at the weekly average.
What is visceral fat?
Fat inside the abdomen around liver, gut and kidneys. It produces inflammatory substances and free fatty acids that burden the liver. It is the fat that disappears first with endurance, less sugar and less alcohol.
Can I be slim and still too fat?
Yes, that is called normal-weight obesity: BMI under 25, but little muscle and lots of belly fat. Common in people who have never trained strength. The waist shows it, BMI does not.
This article is general information and not medical advice. If you have symptoms or existing conditions, or before changing any medication, talk to your doctor.
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