BMI for men: same scale, different story

Why BMI matters for men's health

BMI is a screening tool the NHS uses to estimate whether your weight sits in a healthy proportion to your height.¹ The maths is simple: weight in kilograms divided by height in metres squared.

For men, the resulting number is a starting point rather than an answer. It gives a rough indication of where you sit in relation to cardiovascular and metabolic risk.² Paired with a waist measurement and a few markers that can be measured with a blood test, it gives you a clearer picture.

How BMI differs between men and women

The calculation is identical for everyone, and you can find yours with our BMI calculator. The standard NHS thresholds, 18.5 to 24.9 for a healthy weight, 25 to 29.9 for overweight, and 30 and over for obesity, apply to most adults regardless of sex.¹ Lower thresholds apply to some ethnic groups, which is covered below.

But the same number can mean different things in two different bodies.

Men typically carry more muscle mass than women at the same height and weight, and because muscle is denser than fat, a man and a woman with identical BMIs can have quite different body compositions.³ A man at a BMI of 26 might be carrying less body fat than a woman at 24, even though the chart puts him a category higher.

Fat distribution is the bigger difference. Hormonal differences, including the influence of testosterone and oestrogen, contribute to differences in typical fat distribution between men and women.⁴ Men more often store fat around the abdomen, including the visceral fat packed around the liver, pancreas and intestines. Women more often store fat subcutaneously around the hips and thighs.

That distinction matters. Higher levels of visceral fat are associated with inflammation, insulin resistance and increased cardiometabolic risk.⁴ Two men with identical BMIs can carry very different amounts of it, and have different risk profiles as a result.

Which is why a man's BMI is best read alongside his waist measurement rather than in isolation.

Understanding your BMI as a man

The standard categories

The UK adult ranges are:¹

• Under 18.5: underweight

• 18.5 to 24.9: healthy weight

• 25 to 29.9: overweight

• 30 and over: obese

These apply to most adults, and they're useful as an initial reading. They don't give a full picture of health unless read alongside other measurements.

Ethnicity shifts the threshold

Risk of type 2 diabetes and cardiovascular disease rises at a lower BMI in some ethnic groups. NICE recommends using lower thresholds for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family backgrounds, with a BMI of 23 indicating increased risk and 27.5 indicating high risk.^2,5,6

This reflects differences in how body fat, particularly visceral fat, is distributed at a given BMI across populations, rather than a difference in baseline health.

Visceral fat and waist size

Even with a BMI in the healthy range, it's worth paying attention if you're carrying more weight around your middle than is usual for you. NHS and NICE guidance puts the threshold at 94cm (37 inches), with risk rising further once waist measurement passes 102cm (40 inches).²

To measure properly, find the point halfway between the bottom of your ribs and the top of your hip bones, and read the tape on a normal out-breath.²

Waist-to-height ratio is another quick check worth doing alongside it. As a general guide, aim to keep your waist circumference to less than half your height.² If you're 180cm tall, that means a waist measurement under 90cm.

Key facts: BMI and men's health

• A healthy BMI for most UK men is 18.5 to 24.9.¹

• BMI can overestimate body fat in muscular or athletic men.^3,7

• Both overweight and obesity are associated with an increased likelihood of erectile dysfunction, and obesity is associated with lower testosterone.^9,10

• Men of South Asian, Black, or Middle Eastern descent face elevated risk at a BMI of 23 or above.^5,6

• Men store more visceral fat than women at the same BMI, raising cardiovascular and metabolic risk.⁴

• A waist measurement over 102cm (40 inches) signals increased health risk regardless of BMI.²

The muscle mass caveat

Why muscle skews the number

Muscle is denser than fat, so a kilogram of muscle takes up less space on your frame than a kilogram of fat.³ A man who trains for strength can return a BMI of 27 or 28 while carrying relatively little body fat, because the calculation can't distinguish between the two tissues.⁷

If your BMI puts you in the overweight range but your waist measurement is well within range and you carry a lot of muscle, the category may not reflect your body composition.

When to use waist circumference instead

For active or muscular men, waist circumference tends to be a more useful signal than BMI alone.^2,3 For most men, a waist circumference below 94cm (37 inches) is considered lower risk, while measurements above 102cm (40 inches) are associated with substantially increased health risk.²

Lower waist thresholds apply to men from some ethnic backgrounds, for the same reasons as the BMI thresholds above.^2,6

A DEXA scan or body fat caliper measurement can provide additional information about body composition, though for most men a tape measure around the waist is a practical starting point.

If you want to look beyond the surface, a Numan Complete Blood Test checks the 20 internal markers a BMI calculation can't see, including total testosterone, HbA1c, cholesterol, and triglycerides. That's where the real story of your health lives.

Next steps

If your BMI is 25 or higher, weight is worth taking seriously, especially if it's been creeping up year on year.⁸ Carrying extra weight, particularly visceral fat, is associated with erectile dysfunction, lower testosterone, and heart disease.^4,9,10 Treating the weight often improves the rest.

If your BMI is 30 or above (or 27.5 with a weight-related condition such as type 2 diabetes or hypertension), you may be eligible for a medically supported weight loss programme.²

Start a consultation today to check your availability and see what's available for you.

The numan take

BMI is a useful starting point, especially as a screen for risk that builds quietly with weight. In a male body though, muscle can push the number up without harming your health, while visceral fat can sit invisibly inside a "normal" reading. So pair it with a waist measurement, and ideally a blood test covering testosterone, blood sugar, and lipids. That combination gives you something a single number never will: a real picture of how your body is doing.

References

^{1 NHS. BMI healthy weight calculator [Internet]. London: NHS; 2024. Available from: https://www.nhs.uk/health-assessment-tools/calculate-your-body-mass-index/}

^{2 National Institute for Health and Care Excellence. Overweight and obesity management [NG246]. London: NICE; 2023.}

^{3 Wu Y, Li D, Vermund SH. Advantages and limitations of the body mass index (BMI) to assess adult obesity. Int J Environ Res Public Health. 2024;21(6):757.}

^{4 Neeland IJ, Ross R, Després JP, Matsuzawa Y, Yamashita S, Shai I, et al. Visceral and ectopic fat, atherosclerosis, and cardiometabolic disease: a position statement. Lancet Diabetes Endocrinol. 2019;7(9):715–725.}

^{5 Caleyachetty R, Barber TM, Mohammed NI, Cappuccio FP, Hardy R, Mathur R, et al. Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in England: a population-based cohort study. Lancet Diabetes Endocrinol. 2021;9(7):419–426.}

^{6 WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157–163.}

^{7 Sweatt K, Garvey WT, Martins C. Strengths and limitations of BMI in the diagnosis of obesity: what is the path forward? Curr Obes Rep. 2024;13(3):584–595.}

^{8 Bhaskaran K, Dos-Santos-Silva I, Leon DA, Douglas IJ, Smeeth L. Association of BMI with overall and cause-specific mortality: a population-based cohort study of 3.6 million adults in the UK. Lancet Diabetes Endocrinol. 2018;6(12):944–953.}

^{9 Ng Tang Fui M, Dupuis P, Grossmann M. Lowered testosterone in male obesity: mechanisms, morbidity and management. Asian J Androl. 2014;16(2):223–231.}

^{10 Pizzol D, Smith L, Fontana L, Caruso MG, Bertoldo A, Demurtas J, et al. Associations between body mass index, waist circumference and erectile dysfunction: a systematic review and meta-analysis. Rev Endocr Metab Disord. 2020;21(4):657–666.}