Your jeans feel tight, the number on the scales is higher than it’s ever been and the adverts on your screen promising to ‘bust your belly fat’ seem to be following you round.
But how do you know if you have too much? Take out a tape measure and wrap it around your waist, holding it taut but not tightly.
According to the World Health Organisation, if the number you see is greater than 94cm (37 inches) for a male or 80cm (31.5 inches) for a female, then you’re officially carrying too much belly fat.
It’s well known that global rates of obesity are rising, but slender people can carry excess abdominal fat too. Around the world, four in 10 adults have too much fat around their middle, and it’s a particularly dangerous problem.
Belly fat increases the risk of many medical conditions, including high blood pressure, heart disease and diabetes. Yet, despite a cacophony of voices telling us how to get rid of it, this type of fat seems especially hard to budge.
So, what do we know about belly fat and how to shift it? Scientists have been studying this stubborn tissue type for more than 30 years – here are the top lessons they’ve learned.
1. It's not all bad
There are two basic types of belly fat.
Subcutaneous fat, located just under the skin, is the fat that you can physically pinch. Visceral fat, on the other hand, can’t be manhandled because it’s deep in the abdominal cavity, packed around vital organs such as the liver, pancreas and intestines.
Both store excess energy in the form of lipids, but they’re not passive blobs of tissue that just sit there. Fat is metabolically active. It secretes hormones and signalling molecules that influence the rest of the body.
When fat cells release the hormone leptin, for example, it tells the brain how much energy is stored in body fat.
“It signals to the brain, now you stop eating because my cells are full,” says Dr Camilla Schéele, who studies the links between fat tissue and health at the University of Copenhagen, in Denmark.
The simplistic view is that subcutaneous fat is good, and visceral fat is bad. If subcutaneous fat is a sturdy container that stores lipids safely, visceral fat is the leaky backup – and once it overflows, lipids spill into the bloodstream.
The liver becomes fatty, the body struggles to regulate blood sugar levels, and a chronic, low-level inflammation emerges that can contribute to disease.
In this scenario, visceral fat is the bad guy. “But it’s not the fat tissue itself that is bad,” says Schéele. “It’s the dysregulation of it. It loses its function.”
In healthy amounts, belly fat is good for us. Visceral fat can even be healing. Surgeons sometimes use patches of sheet-like abdominal fat, called omental tissue, to seal holes in the gut.
This works because fat from here contains immune cells that can help to fight infection, and stem cells that can work to repair the tissue. It also releases molecules that stimulate new blood vessels to grow, bringing oxygen and nutrients to the area.
Not just that, sometimes visceral fat cells can also be rewired to act like immune cells.
A recent study found that when mice have a bacterial infection, visceral fat cells located around the lymph nodes start producing nitric oxide, which has anti-bacterial properties.
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2. Your fat can burn itself
Fat cells or ‘adipocytes’ come in three different colours: white, brown and beige.
Belly fat contains mainly white adipocytes, which are used for storing energy as fat. Brown adipocytes, on the other hand, specialise in burning energy.
Think of them as little radiators that come on when the temperature drops. Hibernating mammals and babies have lots of brown fat cells, which they use to stay warm.
Adults have fewer brown fat cells as we’re more capable of warming ourselves. They are located around the neck, shoulders, spine and kidneys, and are associated with good health.
A study of 52,000 people found that those with more brown fat had lower blood pressure and levels of circulating lipids, as well as a reduced risk of developing type 2 diabetes and heart disease.
People with more brown fat are also likely to have less belly fat, and the fat they do have contains more subcutaneous and less visceral tissue.
Wouldn’t it be good if we could harness the positive effects of brown fat, or somehow use it to bust our hard-to-shift belly fat? “The field has been focused on activating brown fat, because when it is active, it can consume lipids and glucose,” says Schéele.
The thing is, belly fat is overwhelmingly comprised of white adipocytes. But it does contain small numbers of the third colour of fat cells.
Beige fat cells are white fat cells that can be activated to function like brown fat cells. Chilling is one way to do this, as tissue culture studies have demonstrated.
Meanwhile, a study of five men who volunteered to sleep in a cold room (19°C/66°F) for a month found their brown fat volume increased by 42 per cent, with a 10 per cent increase in their cells’ metabolic activity.
Sleeping without a duvet is not for everyone. But Schéele has also studied the effects of a brief, cold water dip.
She found that slender, healthy people who practice winter swimming – a pastime much loved by the Scandinavians – burn more energy in response to cold and are better at regulating their blood sugar than non-swimming control participants.
“They also have less belly fat,” she says. This suggests that winter swimming could be ‘browning’ the white cells in their bellies, but more research is needed to unravel the specifics.
Until it does, Schéele says winter swimming could be beneficial for healthy people. “But I would not recommend it for anyone with cardiometabolic disease. Consult your doctor first.”
3. Stress belly is real
We all know that chronic stress is bad for our health, but studies show that people who experience prolonged stress also tend to have more belly fat.
Animal studies have taken this one step further, showing not just that stress is associated with ‘stress belly,’ but that it causes it. Rats that are chronically stressed have been shown to develop more visceral fat in their abdomen than non-stressed rats.
Stress could also help to explain why people who are sleep-deprived have more belly fat.
Dr Naima Covassin studies how sleep affects health. Sleep deprivation is stressful – it makes people eat more and gain weight. But until recently, researchers didn’t know where, exactly, any extra fat is hidden away.
So, Covassin invited 12 healthy, lean people to stay at her lab in the Mayo Clinic in Minnesota, in the US, in two three-week sessions. In the first session, they were allowed to sleep normally. In the other, they had just four hours of shuteye per night.
They could eat what they wanted and there was a three-day gap between the two sessions.
Stuck in the lab with little to do, they all put on weight – but in the three weeks that they were sleep-deprived, they each put on half a kilogram (1.1lb) more. Why? The lack of sleep made them eat an extra 300 calories a day.
This was reflected in the excess belly fat they developed. In both sessions the participants put on extra subcutaneous fat, but the real shock came when Covassin checked their levels of visceral fat.
When they were sleep-deprived they had 11 per cent more visceral belly fat. When they slept normally there was no change here.
“This was surprising and concerning,” she says. “It suggests that fat is being redirected to the more dangerous visceral compartment.” Remember the leaky container? This is not where you want your belly fat to be.
The study suggests that poor sleep is a trigger for excess visceral belly fat. But there’s more bad news. Covassin’s work also links poor sleep with high blood pressure, particularly in women, and she has found that there’s no easy fix for the adverse effects of sleep restriction.
“This opens the conversation about weekend ‘catch-up’ sleep,” she says. While there’s evidence that longer periods of catch-up sleep might help, “we only get two days at the weekend, and this isn’t enough.”
In other words: trying to lower your stress, and prioritising your sleep, could help you keep your fat in check.
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4. Forget spot reduction
Open social media and you’ll find influencers promoting workouts touted to target belly fat.
The idea that we can preferentially lose fat from our bellies, as opposed to elsewhere, is an attractive one. Only, it’s not that simple. Targeted fat loss, also known as spot reduction, doesn’t work.
A 12-week study of 40 overweight women, which compared the effects of diet versus diet with abdominal exercises, found that the belly crunches didn’t actually affect belly fat. Both groups lost weight, but there was no difference in waist circumference or subcutaneous fat.
And it’s not the only one. A 2022 meta-analysis of 13 studies, involving over 1,000 participants, found that localised muscle training didn’t lead to more fat loss in the target area.
The authors concluded, “The popular belief concerning spot reduction is probably derived from wishful thinking and convenient marketing strategies.”
The truth is that when we burn fat, through exercise or some other means, we burn it from all of our fat stores, wherever they may be. But – while spot reduction is a myth – there are a few exercise hacks that could make a difference.
One is to adjust the time that you exercise.
A study of 56 healthy adults compared the effects of morning versus evening exercise. For 12 weeks, they all followed the same meal plan and fitness programme, which included a mix of stretching, sprint, resistance and endurance training.
Everyone’s health improved, but the women in the study lost more belly fat and had lower blood pressure when they exercised in the morning and gained more muscle strength when they exercised in the evening. (This effect was not seen in men, and for now, no one’s exactly sure of the reasons behind this.)
Another thing you can try to help lose belly fat is to tailor the intensity of your exercise.
Interval training – alternating high and low bursts of exercise intensity – has been shown not just to reduce the total percentage of body fat, but also the amount of visceral and subcutaneous belly fat.
This is compared with moderate-intensity continuous training, and is especially pronounced for people who are overweight or obese.
The take-home message? Get exercising.
Remember that exercise aids fat loss all over the body, including the abdomen. Consider interval training. And if you’re a woman, and you can bear it, consider rising early to start that workout.
5. Some foods are (much) worse than others
When it comes to belly fat, sugar and ultra-processed foods (UPFs) are public enemies number one and two.
Sugary drinks are often sweetened with fructose instead of glucose. A six-year study of around 1,000 adults found that people who drank at least one of these types of drink per day accumulated around 27 per cent more visceral belly fat than non-drinkers.
Part of the problem is that fructose is metabolised differently to glucose. Excess fructose goes straight to the liver, where it leads to inflammation, the accumulation of fat and the expression of lipid-forming genes – which then lead to more fat.
Additionally, fructose blunts satiety signals and weakens the lining of the intestine, disrupting the gut microbiome.
UPFs are foods that contain chemicals, colourings and other ingredients not usually found in the home kitchen. Examples include sliced bread, ready meals and processed meats. In the UK, they make up around half of our calorie intake.
UPFs have been linked to many issues, including obesity, stroke, type 2 diabetes, sleep problems, anxiety, depression and early death. They have also been linked to belly fat.
A five-year study of 22,500 people, for example, found that those who ate the most UPFs had a 79 per cent higher risk of becoming obese, and a 30 per cent higher risk of developing abdominal obesity, than those who ate the least UPFs.
Saturated fats and refined carbohydrates – frequent components of UFPs – are also associated with excess belly fat, as is alcohol.
Intermittent fasting has been peddled as a way to budge belly fat, but a study in mice suggests the opposite may be the case. In this case, intermittent fasting actually caused mice to hang onto their abdominal fat, and become more resistant to weight loss.
What might be more effective is going green. After all, people who eat plant-based diets tend to have less belly fat and better metabolic health.
You’ve probably heard of the Mediterranean diet, but if you want to minimise belly fat, go for the Green Mediterranean diet – which favours extra greens and nuts over meat.
A 2022 study found that those on the Green Mediterranean diet lost more than twice as much belly fat than those on the original Mediterranean diet, and over three times more than those eating a regular healthy diet (characterised by lean proteins, healthy fats and high levels of fibre).
6. You can't control everything
Genetics has a big influence on the way body fat is laid down. Genes account for 60 per cent of fat distribution, which means that if you have parents or grandparents with excess abdominal fat, it may predispose you to accumulate fat in the same area.
Genes are not destiny, however. Nor is there a single gene that determines where fat ends up.
Instead, geneticists have identified many different sites in many different genes that combine to influence fat deposition, in the belly and elsewhere.
Sex also influences where fat goes. Women tend to have a larger proportion of body fat than men and store it more around their buttocks and upper thighs, while males are more likely to store their fat around the belly.
Women tend to have more subcutaneous fat, while men have more visceral fat.
And then there’s ageing. As we get older, changes in muscle mass, metabolism and hormone levels all have an impact.
Post-menopausal women and middle-aged men tend to store more fat around their mid-section, and find it a difficult place to lose fat from.
If you’re worried about belly fat, remember that losing weight from any part of your body will improve your health.
“Get enough sleep. Exercise. Expose yourself to fresh air and sunlight. Eat as much homemade food as you can,” says Schéele, “and if you’re healthy and careful, think about adding in a bit of winter swimming.”
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