How do I lose belly fat and get a flatter stomach?

You can’t burn fat from your belly alone. Belly fat goes as you lose fat across your body, and the deep fat around the organs responds especially well to aerobic exercise. Eat a little less than you use, move on most days, and lift so you keep muscle. If your stomach looks bigger by evening than in the morning, that’s often bloating, not fat. To track it, measure your waist: the NICE guide is to keep it under half your height.

Can you lose fat from just your belly?

No. A 2022 meta-analysis pooled 13 studies with 1,158 people aged 14 to 71 who trained one body area, and found no extra fat loss in that area. In a six-week trial, adults did seven ab exercises five days a week: their belly fat and waist didn’t change, though their ab endurance went up.

Sit-ups, crunches and planks make the muscle stronger. Fat loss across the whole body is what uncovers it. If a visible six pack is the aim, see how to get a six pack.

What actually shrinks a belly?

Two things, together: an energy gap and aerobic exercise.

The energy gap takes fat from everywhere, the belly included. The NHS suggests aiming to lose 0.5 to 1 kg a week. Work out a starting figure with the calorie calculator.

Aerobic exercise works on the deep belly fat in particular. A 2013 review of 15 trials of exercise without a diet change found it cut deep belly fat on CT or MRI scans. The five trials that measured it in cm² averaged about 37 cm² in women and 47 cm² in men, and the effect was clear by 12 weeks. Moderate and hard aerobic work did the most; easy work did not clearly help. A 2012 review of 35 trials came to the same view: aerobic exercise reduced deep belly fat, and strength training on its own showed no clear effect.

So walk briskly, run, cycle, swim or play a sport, and count the minutes. The WHO recommends 150 to 300 minutes of moderate activity a week. Lift as well: it keeps the muscle you have while you lose fat. See losing fat and building muscle together.

In Nume: choose Lose body fat. The plan starts with a smaller cut for two weeks, then stays moderate, for loss you can keep up. If you’ve trained steadily for three months or more, you start at the full cut. The movement you already do counts: tell Nume about your walks, runs, classes and sport, and they go into your daily energy, with food planned around each session. Progress shows your movement minutes for the week against the WHO’s 150.

How to measure your waist

The scale mixes fat, water and muscle. Your waist tracks belly fat more directly. NICE, the UK’s health guidance body, gives this method:

Find the bottom of your ribs and the top of your hips.
Wrap a tape around your waist midway between them, which is just above the belly button.
Breathe out naturally, then read the tape.
Divide your waist by your height, both in the same units.

Waist-to-height	What NICE calls it
0.4 to 0.49	Healthy
0.5 to 0.59	Increased
0.6 or more	High

For example, a 96.5 cm waist at 170 cm tall gives 0.57. NICE says the ratio works for men and women of all ethnicities with a BMI under 35, including people with a lot of muscle. Keep your waist under half your height. Measure once a week, at the same time of day, and read the trend.

For the other half of the picture, see the BMI calculator.

Is it fat or bloating?

Bloating comes and goes within a day or a week. Fat doesn’t. If your stomach is flat in the morning and round by night, most of that change is bloating.

The NHS lists the usual causes: gas from some foods and fizzy drinks, swallowing air while you eat, constipation, food intolerances, coeliac disease, IBS, and periods for some people. It suggests:

regular exercise
smaller, more frequent meals instead of large ones
plenty of water
soluble fibre such as oats or linseed if you’re constipated
fewer fizzy drinks, and less alcohol and caffeine
chewing with your mouth closed, so you swallow less air

Fibre matters both ways. The NHS says adults should aim for 30 g a day, and most eat about 20 g. See how much fibre you need.

In Nume: you set your own eating times, from one to six a day, so smaller and more frequent meals are simply your plan. Every meal you log shows its fibre, and Progress shows your fibre each day against a guide of about 30 g per 2,000 kcal, worked out at your own plan. Tell Nume a food that doesn’t sit well with you and it stops planning it.

Does posture change your stomach?

It changes how your stomach looks, not how much fat is there. Standing tall with your trunk lightly braced makes the same stomach look flatter in a mirror or a photo. When you compare photos, take them the same way each time: same stance, same light, same time of day.

Why is my lower belly the last to go?

Everyone stores fat in their own pattern, and it leaves from the whole body at once, not in an order you can choose. The fat you can pinch low on the belly is often the part people notice last. Keep the same pace. Your waist number shows progress that the mirror misses.

What about sleep and drinks?

Sleep changes what you lose. In a small study, people on the same reduced diet lost less than half as much fat with 5.5 hours in bed as with 8.5. More on that in why the scale stops moving.

Drinks carry energy too. Alcohol, juice, milky coffee and sweet drinks add up across a week.

In Nume: drinks you log count in your day like food. Set up something you have most days, like a morning coffee, turn on Log it for me, and it records itself at its time.

Bring it to Nume

A flatter stomach comes from a fat loss you keep up for months, plus the movement you enjoy. Nume plans that with you. Your energy sits a moderate step under what your body uses and follows your latest weigh-in. Meals come from the dishes you eat, at your own eating times, and when one runs heavier, the rest of the day adjusts and says why. Your walks, runs and sport count in your plan, and Progress shows your weight, movement minutes and fibre over the weeks, with private photos beside your weight if you want them. Only you see the photos, and they are never read by AI.

To pick between goals first, see how to choose a goal. If counting every gram feels like too much, see how exact you need to be.

Common questions

Can I get a flat stomach in a week?

Bloating can change in days. Fat can’t: at the NHS pace of 0.5 to 1 kg a week, a week takes off a little. For an event a few weeks away, cut back on fizzy drinks, eat smaller meals and keep your fibre steady, and start the fat loss now.

Do sit-ups or planks flatten your stomach?

They strengthen the muscles. They don’t take fat off the belly. See the first section above.

Why do I have a belly when I’m slim?

People store fat in different places, and some carry more of it around the middle at a normal weight. That’s why NICE uses waist-to-height for anyone with a BMI under 35. If your ratio is under 0.5, you’re inside the healthy band.

Is walking enough?

Brisk walking counts toward the WHO’s 150 minutes, and moderate aerobic exercise reduces deep belly fat. Pair it with an energy gap and some strength work for the best result.

Checked on 12 November 2026 · The Nume team