The short answer: keep your waist to less than half your height. For a man of 178 cm that is a waist under about 89 cm. Measure at the midpoint between your lowest rib and the top of your hip bone, at the end of a normal breath out, tape level and snug but not pressing in. After 50 this number tells you more than the scales, because muscle loss hides fat gain on a bathroom scale. Measure once a week for six weeks, then compare the average.
That is the whole article in one paragraph. What follows is why BMI drifts out of usefulness after 50, how to take the measurement so it means something, and what actually moves it.
Why the tape measure beats the scales after 50
Two things happen to the body around this age, and they push in opposite directions on a bathroom scale. Muscle mass tends to fall unless it is trained, and fat tends to gather around the middle rather than the hips and thighs. Weight can stay flat while the shape of the body changes underneath it, which is why so many men in their fifties report that they weigh the same as ten years ago but nothing fits.
BMI has the same blind spot. It compares weight with height and nothing else. Two men of 178 cm and 90 kg get the same number, even if one carries it as muscle from twenty years of training and the other carries it around his waist. After 50, that difference matters more than the number itself.
The waist measurement is useful because it is a decent proxy for the fat stored around the organs — the fat that sits inside the abdomen rather than under the skin. Waist-to-height ratio, your waist divided by your height in the same units, is the neatest version of that idea: it needs no table, no app and no scale, and it scales sensibly whether you are tall or short. Public health bodies in the UK use it precisely because it is simple enough to be checked in a minute at home.
How to measure it properly
The measurement is only worth taking if it is repeatable, and most people take it in a way that wanders by two or three centimetres from week to week. Do it like this:
- Find the right spot. The midpoint between the bottom of your ribs and the top of your hip bone. That is roughly at the level of the navel, but not always — on many men it sits a touch higher.
- Breathe out normally and take the reading at the end of the breath. Do not hold a big breath in, and do not pull your stomach in.
- Keep the tape level all the way round, parallel to the floor. A tape that dips at the back reads short.
- Snug, not tight. The tape should touch the skin without squeezing it. No clothing, no belt.
- Same time, same way. Once a week, in the morning, before breakfast, after the toilet. Measure twice and take the lower of the two if they differ.
Then divide. Waist in centimetres divided by height in centimetres gives the ratio. A 178 cm man with an 89 cm waist is at 0.50; at 96 cm he is at 0.54.
| Ratio | What the NHS guidance says | For a 178 cm man |
|---|---|---|
| Under 0.4 | Below the guidance line — unusually lean | waist under 71 cm |
| 0.4 – 0.49 | Healthy range | 71 – 88 cm |
| 0.5 – 0.59 | Above the guidance line — worth acting on | 89 – 105 cm |
| 0.6 and over | Well above the guidance line | 107 cm or more |
One honest caveat: a single reading is a snapshot, and waist measurements move with salt, alcohol, hydration and a big meal. Treat the ratio as a long-run signal and compare the average of two or three readings rather than reacting to one bad morning. And if your waist is high but you have never trained, the first move is not a diet — it is protecting the muscle you already have while you add movement.
The six-week tape protocol
Six weeks is long enough to see whether what you are doing is working and short enough to stay interested. The protocol is deliberately dull:
- Baseline (day 1). Measure twice as above and write both numbers down, with the date. Note your steps and how many strength sessions you did that week.
- Weeks 2 to 5. Keep the three working parts going: protein at every meal, a daily step target you can actually hit, and two short strength sessions a week. The full detail is in our nutrition over 50 pillar and in the piece on protein intake after 50.
- Week 6. Measure again, twice, and compare. As long as the direction is right, carry the same routine on for another six weeks rather than changing everything.
What to record, and nothing else: date, waist in centimetres, ratio, average daily steps, strength sessions completed. Four numbers is enough to tell whether the week went the way you intended.
What actually moves the number
Protein at every meal. Protein is the raw material for keeping muscle, and muscle is what keeps fat loss from turning into general shrinkage. The practical version is a palm-sized portion of a protein food at each meal rather than one large serving in the evening.
Steps you will actually do. Daily walking is the least dramatic and most reliable lever there is. A target that fits your real week — say 7,000 to 9,000 steps, built in 1,000-step stages — beats an ambitious number you hit twice.
Two short strength sessions a week. Twenty to thirty minutes, whole body, is enough to protect the muscle that keeps your daily energy expenditure where it was. Our strength guide walks through the basic movements and the dose.
Sleep and alcohol. Both show up around the middle faster than almost anything else. Poor sleep raises appetite for exactly the wrong foods, and beer and wine are easy calories that also disrupt the night. The piece on sleep quality over 50 covers the evening changes that pay off first.
What does not move it
Spot reduction does not work — sit-ups build abdominal muscle, they do not take fat off the waist. Detoxes, teas and appetite suppressants sold for the purpose do not work either, and anything that claims to target belly fat specifically is selling a story. Skipping breakfast and eating one large evening meal tends to work against you, because it makes it harder to get enough protein across the day. And a sudden crash diet is the wrong tool at this stage: the weight that comes off quickly is often muscle you then have to rebuild.
When to take the number to a GP
A high waist measurement is worth a conversation, not a panic. Ask your GP about a general health check if your ratio is 0.5 or more, and particularly if it is 0.6 or above, if your weight has changed without you trying, if you have a family history of type 2 diabetes or heart disease, or if you have high blood pressure. The NHS Health Check offers to adults aged 40 to 74 in England is a sensible starting point. Nothing in this article is medical advice, and a tape measure is a screening tool rather than a diagnosis.
Start with a week, not a programme
The free 7-Day Guide is a week of small, specific actions — one a day, no gym and no gear. The protein, walking and strength habits in this article all start there.
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Common questions
What waist-to-height ratio should a man over 50 aim for?
The NHS guidance is to keep your waist to less than half your height, which is a ratio below 0.5. For a man of 178 cm that means a waist under about 89 cm. It is a screening line rather than a target to hit exactly, and a slow move towards it is worth more than a sudden drop.
Why is BMI less useful after 50?
BMI only compares weight with height, and after 50 the composition of that weight changes. Muscle mass tends to fall while fat gathers around the middle, so two men of the same height and weight can be in very different shape. A tape measure at the waist sees the fat that sits around the organs, which BMI cannot.
Where exactly do I measure my waist?
Find the midpoint between the bottom of your ribs and the top of your hip bone, and measure there. Breathe out normally and measure at the end of the breath, with the tape level all the way round and snug but not pressing into the skin. Do not measure over clothing and do not pull your stomach in.
How fast should the waist measurement change?
Slowly, and not every week. A centimetre or two over six to eight weeks is a good, sustainable pace. Waist measurements move in steps rather than a smooth line, and they jump around with salt, alcohol and a heavy meal, so compare the average of two or three readings rather than a single one.