Being ‘skinny fat’ raises the risk of Alzheimer’s even MORE than typical obesity, small study suggests

Being ‘skinny fat’ raises the risk of Alzheimer’s – perhaps even more so than ostensibly obese people, research suggests.

A small study of 56 middle-aged people found those with greater levels of visceral fat – the type that wraps around abdominal organs deep inside the body – had more danger proteins in their brain linked to dementia than their counterparts who had more flabby fat, called subcutaneous fat.

Visceral fat is known as ‘skinny fat’ because it is not visible from the outside, meaning even people with a healthy BMI can have a significant amount of visceral fat. 

But it can release chemicals and hormones into the blood that cause inflammation, which in turn causes inflammation in the brain, which is one of the main things that leads to Alzheimer’s.

Visceral fat wraps around abdominal organs deep inside the body, whereas subcutaneous fat is under the skin. Even people with a healthy BMI can have a significant amount of visceral fat 

Study author Dr Mahsa Dolatshahi, a post-doctoral research fellow at Washington University in St Louis, said: ‘Even though there have been other studies linking BMI with brain atrophy or even a higher dementia risk, no prior study has linked a specific type of fat to the actual Alzheimer’s disease protein in cognitively normal people.’

Researchers looked at data from 54 cognitively healthy participants aged 40-60 with an average BMI of 32. 

A BMI above 30 is categorized as obese, according to the Centers for Disease Control and Prevention. 

Using an MRI, the volume of subcutaneous fat and visceral fat were measured once.

Subcutaneous fat is the wobbly type of fat that lies just under the skin and causes cellulite to form.

This type of fat is actually the least harmful and tends to accumulate around the thighs and buttocks rather than the gut, creating a pear-shaped physique. 

Unlike visceral fat, subcutaneous fat does not release chemicals and is the layer between the skin and muscle. 

An MRI of participants’ brains also measured the thickness of the cortex, the layer of the brain in charge of speech, long-term memory, perception and judgment. As Alzheimer’s gets worse, this layer becomes thinner. 

At the same time, PET scans were also used in a subset of participants to see whether amyloid and tau proteins were at higher levels.

A positron emission tomography (PET) scan is used to check for signs of brain disorders, as well as heart disease and cancer. 

Amyloid and tau are proteins thought to interfere with the communication between brain cells and are key markers of Alzheimer’s.

The researchers compared the fat measurements and the brain scans and found that participants with more visceral fat had more amyloid in their brains, indicating that they might be at higher risk for Alzheimer’s disease. The relationship was worse in men than women. 

Researchers found that this fat is related to changes in the brain in participants as early as age 50 – up to 15 years before the earliest memory loss symptoms of Alzheimer’s disease. 

The researchers plan to follow up on the study’s participants to track the long-term impact of visceral fat since the earliest development of Alzheimer’s in the brain can appear up to 20 years before the first symptoms appear.

Senior study author Dr Cyrus Raji, associate professor of radiology and neurology, said the findings could help with earlier diagnosis of Alzheimer’s and potential treatments.

He said: ‘It shows that such brain changes occur as early as age 50, on average – up to 15 years before the earliest memory loss symptoms of Alzheimer’s occur.’ 

The study was presented at the annual meeting of the Radiology Society of North America.

More than six million Americans have Alzheimer’s, according to the Alzheimer’s Association, which is set to rise to 13 million by 2050.