Hidden deep abdominal fat leads to smaller brains, study finds

High visceral fat levels in middle age shrink your brain and put you at high risk of dementia - so how can you reduce this dangerous fat?

Exercise is effective in reducing visceral fat.

People with excessive amounts of fat distributed around the organs are likely to have smaller brains in later life and face a higher risk of dementia.

That’s the finding of a Monash University study that has added to growing evidence that inflammatory processes within the brain thought to be linked to dementia may be intricately linked to visceral fat.

Visceral fat is the most dangerous type of adipose tissue that is sometimes described as “hidden fat”. It is found deep within the abdominal cavity and surrounds the organs, including the stomach, liver and intestines. It can also build up within the arteries.

Even slim people can have high levels of visceral fat if they are unfit or eat an unhealthy diet. Visceral fat is sometimes spoken of by medics and scientists as a hormonally active type of body fat, as it operates in the body effectively as an endocrine system, releasing hormones and inflammatory molecules.

This is the likely reason it’s been found to be associated with the development of dementia, said Velandai Srikanth, a professor at Monash’s National Centre for Healthy Ageing and a co-lead of the study published on Wednesday in the journal Diabetes Obesity and Metabolism.

“This fat has actually quite an active endocrinology,” said Professor Srikanth.

“It produces lots of hormones, and inflammatory cytokines, chemicals which promote inflammation. And they can be the underlying source of development of problems like dementia.”

The Monash University study drew on abdominal and brain MRI data from a 17,300 people aged 40-69 years of age in the UK Biobank. It compared mid-life abdominal fat from the subjects and brain ageing later in life, finding that fat hidden around the organs was associated with smaller brains, with the effect being more pronounced in men than women.

Those with higher levels of visceral fat were also found to have lower hippocampal volume. The hippocampus is the area of the brain that controls learning and memory. These people also had greater white matter lesion volume, which is associated with small vessel disease and affects the speed of cognition. “Chronic inflammation (has) long been hypothesised as a mechanism underlying the development and unhealthy brain of dementia.” Professor Srikanth said.

“So far there has been no real direct evidence looking at humans. This research … starts to give us some flavour of why that might be happening. The other thing is that the nature of the relationship between abdominal fat and brain measures might be different in men and women.

“If you look at grey matter volume, which is an overall sort of collection of neurons in the brain … important for a lot of functions of the brain, the relationship between visceral fat and lower grey matter volume seems stronger in men than in women, which may mean that men who have more visceral fat are more at risk.”

Waist circumference is strongly associated with visceral fat levels. Women with a waist measure­ment more than 88cms are at higher risk and for men, over 102cms is concerning (these measurements are based on caucasian people).

Professor Srikanth said the study indicated that if interventions were put in place in middle age, there was plenty of time to reduce visceral fat levels.