Losing belly fat as a man: what works and what you can measure

Your tape measure says 104 centimetres. The scale says 88 kilos, exactly the same as last year. For losing belly fat as a man, that first number is by far the more interesting one.

I think the scale is the most overrated device in the bathroom. It adds up muscle, water and fat. Where that fat sits, it never tells you.

And the location is what decides what happens in your blood.

Visceral fat, the fat around your organs, ties more closely to your blood values than the fat just under your skin. A consensus statement in Nature Reviews Endocrinology argues that waist circumference should be treated as a vital sign, alongside weight (Ross, PMID 32020062).

Why do men store fat around the belly?

Men lay down fat around the belly and the organs sooner, women sooner on hips and legs. Sex hormones drive most of that difference. So a man at a normal weight can still carry plenty of visceral fat, and that fat ties more closely to your sugar and lipid values.

Visceral fat is not a passive store. It is active tissue that releases substances which affect your metabolism. That's why a larger waist often comes with unfavourable triglycerides and a higher blood sugar.

The RIVM tracks overweight in the Netherlands and reports that around half of adult men carry too much weight. That is not a judgement, it is context. You're far from the only man with trousers that pinch.

Age plays a part. From roughly your thirties you slowly lose muscle if you do nothing, and muscle burns more than fat. You eat what you ate at 25, but your body handles it differently.

How do you measure belly fat without a scale?

With a tape measure, not with a scale. Measure standing, on bare skin, halfway between your lowest rib and your hip bone, and breathe out calmly. In men, a waist above 102 centimetres is widely seen as a point of attention, with 94 to 102 centimetres as the borderline zone.

The Voedingscentrum explains how to take that waist measurement and why it says something different from your BMI. Do it at a fixed moment, for example in the morning before breakfast. That way you compare like with like.

Ross and colleagues describe how weight and waist together tell you more than either alone (PMID 32020062). A man can lose weight and still lose little around his middle. And the other way round, your waist can shrink while the scale stands still.

That second scenario is exactly where men give up. Say you train for 12 weeks, the scale drops 3 kilos and then stops. Meanwhile your waist went from 104 to 98 centimetres, and nobody measured it.

Six centimetres is a big difference. You just never saw it.

What actually works to lose belly fat as a man?

An energy deficit you can hold for months, enough protein, and movement that fits your life. No exercise pulls fat specifically off your belly. If your total fat mass drops, your visceral fat usually drops with it, often a little faster than the fat under your skin.

In the Diabetes Prevention Program, participants followed a lifestyle approach with modest weight loss and around 150 minutes of movement a week. Their risk of type 2 diabetes was 58 percent lower, more than with medication in the same study (Knowler, PMID 11832527). That's not diet marketing, that's a large randomised trial.

What seems to help most in practice:

• A deficit you can hold for months, instead of a three-week crash diet.
• Enough protein, so you keep muscle while you lose fat.
• Strength training alongside your cardio.
• Sleep. Short nights make hunger and quick choices a lot easier.
• Fewer liquid calories, because beer and soft drinks add up fast.

The Voedingscentrum and the Hartstichting both point at the same boring foundation. Normal portions, less alcohol, more movement.

Boring works. That is my honest opinion after years of looking at blood results. Men who keep something simple going see their values move, men with the perfect plan drop out in March.

Supplements are a side note here. Which ones do something, and which blood value goes with them, is covered in our piece on supplements for men. Fish oil may lower your triglycerides, for example, but it takes no centimetre off your waist (omega 3 and your blood values).

These are general insights, not personal treatment advice. If you take medication or something else is going on, talk to your GP before changing big things.

Which blood values change when you lose belly fat?

Your triglycerides often fall first, your HbA1c follows more slowly. With a fatty liver your ALT may drop, your SHBG usually rises, and your testosterone can climb after substantial weight loss. The table below gives a rough picture, not a promise, because it differs per man.

The value that usually reacts fastest is your triglycerides. They swing with what you eat and drink. A few weeks of less alcohol and fewer fast sugars often shows up.

Your HbA1c is slower, because it is an average over two to three months. Measure after six weeks and you're still half looking at your old life. What the value means is covered in our piece on the HbA1c value.

Your SHBG belongs on this list too. A low SHBG often goes together with insulin resistance. If you don't know its early signals, read recognising insulin resistance.

Take two men of 44 with exactly the same waist of 101 centimetres. One has triglycerides of 0.9 mmol/l, the other 2.7 mmol/l. Same tape measure, a very different story inside.

That's the point of measuring alongside measuring. Your waist tells you where you stand, your blood tells you what it's doing to you. The second man can be heading somewhere else entirely on the same trouser size.

Why belly fat can lower your testosterone

In fat tissue, the enzyme aromatase converts testosterone into oestrogen. More belly fat means more aromatase, and that can push your testosterone down. A lower testosterone then makes it easier again to lay down belly fat, which creates a loop that feeds itself.

The good news is that the loop turns both ways.

Corona and colleagues pooled studies of men who lost weight through lifestyle or bariatric surgery. Weight loss went together with a rise in total testosterone, and the effect was larger when more weight came off (PMID 23482592). That is not a treatment, but it is one of the few knobs you can turn yourself.

Don't expect miracles. With modest weight loss the rise is often small, and the studies with the biggest effects involved substantial loss. Still, I find this the most motivating part of the story: your waist and your hormones are linked, and that link also works in your favour.

If you want to understand the triangle of belly fat, insulin and testosterone better, read our piece on belly fat and your hormones. Your total testosterone says little, by the way, without your SHBG next to it.

How fast do you see change in your blood?

Faster than you think with your fats, slower than you hope with your hormones. Triglycerides often move within four to eight weeks. HbA1c needs around three months because it is an average, and testosterone usually responds only after substantial and lasting weight loss.

That difference in pace shapes your expectations. Look at everything after six weeks and it seems like little is happening. Look after three months and you get a fairer picture.

There is one catch. Right after you lose weight, some values can sit differently than you expect, partly because your body is still shifting fat around. One unusual result is never a final verdict.

Some men choose to record a baseline first, simply so they can compare later. The Metabolic Health Check looks at your glucose, your HbA1c and your fats, among other things.

What doesn't work?

Sit-ups pull no fat off your belly. Spot reduction doesn't exist, because your body decides where it takes fat from. Ab exercises make the muscle underneath stronger, but the fat layer on top stays put as long as your total fat mass stays the same.

What else delivers less than the packaging promises:

• Fat burners and slimming teas. The evidence is thin and the effects are small.
• Sweat belts and sauna trousers. You lose water, sometimes half a kilo, and it's back after two glasses of water.
• Cardio only, without strength training. You more often lose muscle too, and that's what you want to keep.
• Crash diets. They work briefly, and for most men the weight comes back.

One bad week throws nothing off, by the way. Belly fat builds over years and comes off over months, not days. Be patient with yourself and watch the direction, not the day.

Want to start concretely? Grab a tape measure tonight and measure your waist halfway between your lowest rib and your hip bone. Write the number down with the date, and measure again in twelve weeks at the same time of day.

Always discuss an unusual blood result with your GP. They can help you decide whether further steps are needed.

References

• Ross R, et al. Waist circumference as a vital sign in clinical practice: a Consensus Statement from the IAS and ICCR Working Group on Visceral Obesity. Nat Rev Endocrinol. 2020. PMID 32020062.
• Corona G, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. Eur J Endocrinol. 2013. PMID 23482592.
• Knowler WC, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002. PMID 11832527.
• RIVM. Overweight: figures and context. 2024. rivm.nl
• Voedingscentrum. Measuring waist circumference and healthy weight. 2024. voedingscentrum.nl

Every blood test result at Caliber includes a professional assessment by a BIG-registered doctor. For treatment decisions, always discuss your results with your GP.