A 2020 study found that when belly fat goes above average it can lead to a 39 per cent increased risk of dementia within 15 years compared with those people who have a normal waist circumference.

Singapore study finds extra belly fat in Asians impacts their ability to learn

Now a new study finds that people with higher levels of abdominal body fat are at greater risk of suffering brain atrophy with age.

Cyrus Raji, assistant professor of radiology and neurology at Washington University School of Medicine and one of the study authors, explains.

“A higher amount of abdominal fat is thought to be linked with brain shrinkage because excess fat increases the amount of inflammation in the body.

“This increased inflammation, especially when chronic, is linked to increased brain atrophy” – and so potentially a higher dementia risk later.

This is one reason, he explains, why being overweight during midlife – that is, in your forties and fifties, 20 years before you may exhibit symptoms of cognitive decline – can lead to dementia in later life.

David Merrill, director of the Pacific Brain Health Centre which was also part of the study, says the build-up of abdominal fat is often a “proxy measure of other suboptimal health behaviours” – such as poor diet, excess calorie intake, insufficient physical exercise and high consumption of ultra-processed foods which are full of “empty” calories and trans fats.

Nutrition and wellness coach Amanda Corse of Fizz Fitness in Tanzania, East Africa, explains.

“When we eat more calories than our body needs to burn for energy, particularly sugary or fatty foods, our body has a nifty system of storing it away for later energy requirements, usually in adipose tissue beneath the skin” – that is, subcutaneous fat.

“Consistently overindulging and not getting enough movement in your life, along with high stress and poor sleep, can prompt the build-up of the more dangerous visceral fat” – sometimes called “hidden fat” because it hugs the organs in your abdominal cavity, including the liver and intestines – she says.

This type of fat is linked to diabetes, heart disease and stroke – and now, it seems, to dementia too.

Ideally, Corse says, you want to keep visceral fat to below 10 per cent of your total body fat. If it begins to creep up, “it’s doubly important to pay attention to your lifestyle”.

Why fat around the middle specifically, though, and not fat around the buttocks or thighs, say?

“Most of the fat in the human body – whether we are talking about subcutaneous fat or visceral fat – is stored in the abdomen,” Raji says.

He shows whole-body MRIs of two 61-year-old women – one with a high level of visceral and subcutaneous fat, the other with a normal amount of fat.

The amount of brain atrophy evident in the woman with higher body fat is staggering; her brain MRI shows wide-open blank spaces.

Did the study suggest women were more susceptible this time, too? Yes, he says.

“We did find a sex difference whereby women have a higher magnitude of brain shrinkage than men in relation to increasing abdominal fat,” he says. This needs further investigation, he adds.

Corse’s 5 tips to trim your midsection to avoid brain shrinkage

1. Eat a wide variety of vegetables, lean protein and good fats, and avoid ultra-processed foods which are full of salt and sugar.
2. Intermittent fasting may help your body mobilise and get rid of those tricky fat cells.

3. Do resistance training three to four times a week and cardio a couple of times a week for at least half an hour. Resistance training extends what’s called the “after burn” – that is, your body’s ability to burn fat and carbohydrates even after the resistance session has ended – and it builds muscle, which helps elevate your resting metabolic rate.

4. Make sure you get enough sleep.
5. Keep stress low, as cortisol – there’s that inflammatory hormone again – can increase visceral fat.