Regular exercise may shift belly fat from harmful to healthier types. Photo / Getty Images
A new American study suggests some middle-age-spread is more harmful than others – here’s how to tell the difference
However we try to hide it with ferocious Lycra knickers or a baggy top, there’s no escaping the squishy area of flesh that accumulates around our middle from midlife onwards. Every decade gives it a different name: middle age-spread, muffin top, beer belly or wine-waist – but cheerful as the nicknames may be, the consequences of belly fat are potentially serious. Received wisdom is that accumulating fat around the centre of our body as a product of fine-living is simply not good for our physical health.
In most people, 90% of fat is the kind that lies in a layer just beneath the skin, and this is known as subcutaneous fat. The flesh you can wobble on your thighs or the top of your arms is subcutaneous fat. Even the inch you can pinch on your stomach is probably of the same type.
But the remaining 10% – which is known as visceral or intra-abdominal fat – lies out of reach, beneath the firm wall of your abdomen and wrapped around your internal organs. This is the dangerous kind.
“Abdominal fat is mechanistically linked with a number of conditions, but is also a marker for them,” says Dr James King, a senior lecturer in exercise physiology at the University of Loughborough. “This includes Type 2 diabetes, heart disease and various cancers.” In general, men have more abdominal fat than women – though post-menopause, women increasingly store fat around their middles and their “fat to body” ratio increases more rapidly than it does in men.
Standing on the scales doesn’t tell the whole story. You won’t necessarily gain weight as your belly blooms, though your waistline might grow as visceral fat pushes out against the abdominal wall.
But an American study published earlier this year may help us counter the belly-fat dejection. It seems that not all belly fat is created equal and that we may even be able to change the composition of our abdominal fat without having to enter a life of ascetic self-denial.
Dr Jeffrey Horowitz is professor of movement science at the University of Michigan school of kinesiology. “Our study found that people who exercised regularly and over long periods showed positive effects on their adipose [fat] tissue in overweight or obesity,” he says. “As well as being a means to expend calories, exercising regularly seems to modify your fat tissue in a way that allows you to store your body more healthfully if and when you do experience some weight gain – and nearly everyone does as they get older.”
The study examined and compared belly fat samples from two groups of adults who – to the naked eye – looked similarly overweight, especially in the central area. But one group exercised four times a week and the other did not. “The exercisers had more ‘good fat’,” says Horowitz. “It seems that their efforts increased the capacity to store fat under the skin – or subcutaneously – as opposed to around their organs.”
So, can you tell how much visceral fat you have? And does this encouraging new study mean we can stuff ourselves with fancy crisps, as long as we then go crazy at the gym? Here’s what the experts say.
Visceral fat is stored in the omentum, an apron-like flap of tissue that lies under our belly muscles and covers our intestines. The omentum gets harder and thicker as it fills with fat. “We used to think this fat was just ‘empty storage’, but newer studies have shown that this type of fat is a biologically active organ that secretes harmful hormones,” says King.
A growing body of research has linked visceral fat to a surprisingly wide variety of diseases. “Visceral fat interferes with the functions of the kidney and liver,” says King. “It contributes to diabetes and circulatory diseases, as well as high cholesterol.” Visceral fat makes proteins called cytokines, which can trigger inflammation, a risk factor for heart disease and other chronic conditions.
A study reported in Harvard Health that looked at women between the age of 45 and 79 concluded that those with the biggest waists (and those with the largest waists in relation to their hip size) had more than double the risk of developing heart disease. Abdominal fat also raises the risk of asthma, dementia, breast and bowel cancer.
“We need to reframe the way we look at all fat,” says Horowitz. “Some subcutaneous fat is good for you. It protects your body and serves as an energy source. Only 20% of healthy fat tissue is actually made of fat cells, the rest is made of collagen that has a lower inflammatory profile. This tissue is also full of capillaries that remove waste from the body.”
However, Horowitz makes clear this is only the case with subcutaneous fat that develops under the skin, rather than around the organs.
“You can’t tell where your fat is by looking in the mirror,” says Horowitz. “It’s even pretty hard to decipher this in an imaging study.” Despite this, a quick Google will bring up a raft of adverts for easily-available scans that promise to show how much visceral fat you have.
Dexa scans, for example, were created to measure bone density, but some practitioners now market them as a pricey private way of looking at fat composition. “It’s not that easy to use a Dexa scan to give you the real nitty gritty of where your fat lies,” says King. “The most accurate way of doing this is via a CT scan or full-body MRI, but these are expensive and most doctors won’t agree to perform them for this purpose.”
The best way to monitor your belly fat, says King, is to keep an eye on your waist circumference. “If you feel your jeans are getting tight, this suggests you are putting on weight in the central area,” he says. For a more detailed analysis, measure your waist circumference by wrapping a tape measure around your waist just above your hip bones. For women, 35 inches or more means you’re at risk for health problems stemming from visceral fat. For men, the number is 40 inches or more.
Then, measure your height and divide it by your waist measurement. A ratio over 0.5 to 0.59 suggests that you have excess fat around your belly. And if your ratio is 0.6 or above, your risk is even higher.
“For a layperson, this is a pretty good way of telling whether you are at risk,” says King. “It won’t necessarily tell you if the fat is subcutaneous or visceral, but it’s pretty likely that a large waist circumference is an indication that you have some harmful abdominal fat.”
“It’s clear that living a physically active lifestyle can equate to a more healthy fat tissue,” says Jeffrey Horowitz. The good news is that while we tend to put on visceral fat more quickly than subcutaneous fat, research suggests we also start to lose it rapidly when we address our lifestyles – particularly through exercise.
So are there specific exercises that can help? Spot exercises, such as sit-ups, can tighten abdominal muscles but won’t get at visceral fat (and liposuction for cosmetic fat removal doesn’t reach inside the abdominal wall). “It’s unfortunately not possible to target one area or type of fat,” says King. “To lose weight, you simply need to have an energy deficit, i.e. expend more calories than you take on board.”
Both King and Horowitz suggest that endurance exercise – such as brisk walking, jogging, cycling or rowing – is probably more effective than resistance training such as weights, which burns fewer calories. A 2021 meta-study published in the journal Obesity indicated there was no significant difference between regular exercise and high-impact exercise, so there’s no need to go crazy.
However, an important point to note: exercise alone will not be sufficient in a programme of global weight loss. The 2021 Obesity study also notes that exercise is capped at an overall weight loss of between 1.5kg to 3.5kg. Hence, a healthy diet remains important in the overall maintenance of a healthy weight and fat composition.
Ultimately, James King welcomes Horowitz’s Michigan study and while he points to some limitations – that the study was “cross-sectional”, rather than “cause and effect”, meaning that it didn’t show visceral fat turning into subcutaneous fat in real time – he feels it’s encouraging news. “Anything that adds to the story of ‘exercise is medicine’ has to be a good thing,” says King. “It shows yet another benefit to being active.”
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