Body fat percentage: what is normal for your age and sex

Body fat percentage chart by sex and age

The chart at the top comes from the LEAD study (Ofenheimer and colleagues, Eur J Clin Nutr, 2020): 10,894 adults aged 18 to 81 from a population cohort in Austria, all measured on the same DXA model. It is one of the few European references made with a laboratory method in the general population rather than in gym volunteers. What it shows at a glance: women carry more fat than men at every age, about 9 points on average (38.3 versus 29.3%), and in both sexes the percentage rises over the years. But an average is not a healthy range. That is why this second table brings together the other figures you will come across, each with what it is and where it comes from.

• Women aged 18 to 29 in the LEAD study averaged 34.9% body fat and men 24.8%: a 10-point gap from a young age
• At 70 to 81, 43.0% in women and 33.6% in men: about 8 to 9 points more than at 18 to 29 in both sexes
• The US sample from Imboden comes out leaner than the Austrian one at the same age (an average of 31.4% in women aged 20 to 29, versus 34.9%): a different population and a different machine
• Every reference is split by sex: compare your number only with that of your own sex

The average is not the healthy figure: the obesity threshold by body fat

This is the trap in the word "normal". In the LEAD study, the average for men, 29.3% fat, is already above the threshold many studies use for obesity by body fat: over 25% in men and over 35% in women. It is the criterion the Romero-Corral team (Int J Obes, 2008) uses as the WHO reference. The same goes for women: their average is 38.3%. It is not an error in the chart, even if it was measured with another device: those men had an average BMI of 26.6, in the overweight range. What is typical in a population is not the same as what is healthy. As a health reference, the one from Kyle and colleagues (Nutrition, 2003), with 5,635 healthy people in Switzerland, gives the body fat of those with a normal BMI: 24.6 to 33.2% in women and 13.4 to 21.7% in men. It is a range under a specific condition (a normal BMI), measured by bioimpedance, not a personal goal. If you want the why of BMI and its limits, it is in what BMI is and why it does not tell the whole story.

How body fat changes with age

If you search for "body fat percentage by age", the short answer is that it goes up: in the LEAD study, from 34.9% in women aged 18 to 29 to 43.0% in those aged 70 to 81, and from 24.8% to 33.6% in men. What grows most is not the fat you can pinch but the fat around your organs. Visceral fat, measured with the same DXA, went from about 425 g on average in men aged 18 to 29 to about 2,038 g in those aged 70 to 81, and from 236 g to 1,147 g in women: almost five times as much in both sexes. That is why, with age, your waist sometimes says more than the scale. It is what the waist-to-height ratio calculator measures, and the why is in visceral fat: what it is and how to reduce it.

• Women (LEAD): 34.9% at 18-29, 35.5% at 30-39, 37.4% at 40-49, 39.9% at 50-59, 42.3% at 60-69 and 43.0% at 70-81
• Men (LEAD): 24.8%, 27.7%, 29.8%, 31.3%, 32.7% and 33.6% in the same age groups
• In the Imboden sample, the median for women went from 29.9% at 20-29 to 42.7% at 50-59, and for men from 20.2% to 31.4%

How it is measured: DXA, bioimpedance scales and a tape measure

None of the methods you can use at home actually sees fat: they estimate it. DXA (dual-energy X-ray absorptiometry) separates fat, lean tissue and bone in the image, and it is the basis of the LEAD and Imboden charts. Bioimpedance scales send an imperceptible current through the body and work out fat with their own equation, which changes with the brand and with the population it was calibrated on. It is the same reason the "muscle mass %" on your scale does not match the studies, as explained in what muscle mass percentage is normal. And the tape measure, with the US Navy method (neck, waist and, in women, hips), is what the body fat calculator uses: it needs no device, but it is also an estimate.

• DXA: a laboratory and clinical method; two different brands can give the same person different numbers
• Underwater weighing: the laboratory classic; it works out fat from body density, because fat floats and the rest sinks
• Bioimpedance (your scale or the one at the gym): convenient and cheap; useful for following the TREND on the same device, not for comparing yourself with a chart made by another method
• Tape measure: cheap and repeatable if you always measure at the same spot; it gives an estimate, not a measurement

Does muscle weigh more than fat?

A kilo is a kilo, whether it is muscle or fat. What changes is how much space it takes up. Body composition models assume that fat has a density of 0.9007 g/cm³ and fat-free mass (muscle, bone, organs and water) 1.1000 g/cm³ (Kuriyan, Indian J Med Res, 2018). Doing the maths, a kilo of fat takes up about 1.11 litres and a kilo of fat-free mass about 0.91: fat takes up 22% more room. It is the same principle as underwater weighing. That is why two people of the same weight can wear different sizes, and why, if you train for strength and eat well, your waist can shrink while the scale barely moves.

What to do if your percentage comes out high

First, make sure the number belongs to you and not to the device: repeat it under the same conditions for a few weeks and look at the trend. If it stays above the ranges above, what brings it down is the usual, with no shortcuts: a calorie deficit you can sustain, strength training to keep your muscle while you lose fat, and moving every day. In the Norwegian HUNT4 study, regular physical activity went with less fat mass in every age group and in both sexes. It is an association, not proof of cause, but it points the same way as everything else.

1. 1

   Measure the same way and watch the trend

   Same method, same time and same conditions, once a week. A single scale reading says very little; with a tape measure, the body fat calculator gives you a repeatable estimate.

2. 2

   Work out a deficit you can sustain

   The pace and the calories come from the weight loss calculator, and the why from the calorie deficit explained.

3. 3

   Train for strength

   It helps make sure what you lose is fat and not muscle. There is a starting point in body recomposition.

4. 4

   Keep an eye on your waist

   Over the years the fat that rises most is visceral fat, and your waist reflects it better than your weight: check it with the waist-to-height ratio calculator.

In short: in 10,894 adults in Austria measured by DXA, the average was 38.3% body fat in women and 29.3% in men, and it rises with age; but that average is already above the threshold many studies use for obesity (over 35% in women and 25% in men), so do not take it as "healthy". With a normal BMI, Kyle's reference range is 24.6 to 33.2% in women and 13.4 to 21.7% in men. Each device has its own scale: compare your number with yourself, on the same method. And since fat is gained or lost through what you eat every day, knowing what you really eat matters more than the decimal point: with a photo of each plate, Renzy gives you the calories and protein without weighing anything.