Waist-to-height ratio: the measurement that says more than weight
Your waist-to-height ratio is your waist circumference divided by your height, in the same unit. The British National Institute for Health and Care Excellence recommends it, alongside body mass index, for adults with a body mass index below 35, and gives three categories: 0.4 to 0.49 indicates healthy central adiposity, 0.5 to 0.59 increased central adiposity, and 0.6 or more high central adiposity. The practical rule is to keep your waist to less than half your height. To measure it, stand, breathe out normally, and pass a tape around your body midway between the bottom of your ribs and the top of your hip bones. A man of 180 centimetres should have a waist under 90. The ratio matters because fat carried around the abdomen is more closely linked to diabetes, high blood pressure and heart disease than weight alone.
Your waist-to-height ratio
Measure your waist midway between the lowest rib and the top of the hip bone, after breathing out. Use the same unit for both measurements.
- Waist-to-height ratio
- 0.52
- NICE classification
- Increased central adiposity
- Waist to stay under
- 90 cm
Categories from NICE guideline NG246. Not suitable in pregnancy or with a body mass index above 35.
Why weight and body mass index are not enough
Body mass index, weight in kilograms divided by the square of height in metres, is simple and useful across populations. The World Health Organization defines overweight as a body mass index of 25 or more and obesity as 30 or more.
For an individual, it has two blind spots.
- It does not distinguish fat from muscle. A man who lifts weights can have a body mass index of 27 with little fat.
- It does not say where the fat is. Two people with the same index can carry very different amounts around the abdomen.
The second matters most. Fat stored inside the abdomen, around the organs, is metabolically active in a way that fat under the skin of the hips and thighs is not. It is associated with insulin resistance, raised blood pressure, abnormal blood lipids and cardiovascular disease. Many men in their forties and fifties with a "normal" body mass index carry too much of it.
How to measure your waist correctly
Trouser size is not a measurement. The waistband sits below the abdomen and has been doing so more comfortably each year.
- Stand upright, feet together, abdomen relaxed.
- Find the bottom of your ribs and the top of your hip bones at the side.
- Place the tape midway between the two, horizontal all the way round. For most people this is close to the navel.
- Breathe out normally and read the tape without pulling it tight.
- Measure twice. If the readings differ by more than a centimetre, measure again.
Take the measurement in the morning, before eating, and repeat it monthly under the same conditions.
Reading the ratio
Divide the waist by the height. The calculator above does it and gives the category.
- 0.4 to 0.49: healthy central adiposity. No increased health risk from this factor.
- 0.5 to 0.59: increased central adiposity. Increased health risk.
- 0.6 or more: high central adiposity. Further increased health risk.
These boundaries come from the guideline of the National Institute for Health and Care Excellence on overweight and obesity. They apply to both sexes and to all ethnic groups, which is one advantage of the ratio over fixed waist thresholds. The guideline suggests explaining it in one sentence: keep the size of your waist to less than half of your height.
It is not suitable for people with a body mass index above 35, in pregnancy, or for children under five.
What moves the number
Abdominal fat responds to the same measures as fat elsewhere, and often responds first.
- A moderate energy deficit, maintained. See calorie needs.
- Aerobic activity. It reduces abdominal fat even when weight changes little. See how much exercise per week.
- Strength training, which preserves muscle while fat is lost. See strength training for executives.
- Less alcohol. It adds energy and is strongly associated with abdominal fat in men. See alcohol and training.
- Sleep. Short sleep increases appetite and favours abdominal fat gain. See sleep for executives.
Abdominal exercises strengthen the muscles of the trunk. They do not remove the fat that covers them. Fat is lost from the whole body according to patterns that are largely inherited.
A realistic rate of change
A loss of half a kilogram a week, sustained, typically takes about one centimetre off the waist every one to two weeks at first. For a man of 180 centimetres with a waist of 100, reaching 90 is a matter of several months, not weeks.
Measure monthly. Weekly measurements vary by a centimetre for reasons that have nothing to do with fat: a large meal, salt, the time of day.
Why this matters at 45
The years between 40 and 55 are when abdominal fat accumulates fastest in men, and when its consequences begin to appear on blood tests: fasting glucose creeping up, triglycerides rising, blood pressure at the upper edge of normal. In women, the shift occurs around the menopause.
These changes are silent and reversible at this stage. They are also the main reason a routine medical check after 40 is worth the morning it takes.
Beyond the tape
More precise measurements exist. Dual-energy X-ray absorptiometry gives fat and lean mass by region, including an estimate of visceral fat. It is useful to document a starting point and to check that weight lost is fat rather than muscle. Bioimpedance scales are convenient and imprecise; follow their trend, not their absolute figures.
For most people, a tape measure used the same way each month provides nearly all the useful information.
What the ratio does not tell you
It is a screening measure. A ratio of 0.48 does not guarantee good health, and one of 0.52 in a muscular person with normal blood tests is not an emergency. Blood pressure, blood lipids, blood sugar and fitness complete the picture. See VO2 max.
A waist-to-height ratio of 0.5 or more is a reason to discuss your cardiovascular and metabolic risk with a physician.
Questions
What is a healthy waist-to-height ratio?
Between 0.4 and 0.49, according to the National Institute for Health and Care Excellence. A ratio of 0.5 to 0.59 indicates increased central adiposity and 0.6 or more indicates high central adiposity, each with a correspondingly higher health risk. The simple rule is to keep your waist measurement below half your height, for both men and women.
Where exactly do I measure my waist?
Midway between the bottom of your ribs and the top of your hip bones, which for most people is close to the navel. Stand upright, breathe out normally, keep the tape horizontal and do not pull it tight. This is higher than where trousers sit, so your waist measurement is usually larger than your trouser size suggests.
Is waist-to-height ratio better than BMI?
It adds information that body mass index does not give. Body mass index cannot tell fat from muscle or show where fat is carried, whereas the waist reflects abdominal fat, the kind most closely linked to diabetes and heart disease. Guidelines recommend using both: the ratio for people whose body mass index is below 35.