New Delhi, Dec 2 (IANS): US researchers have, in a study on Monday, found a link between hidden belly fat, known as visceral fat, and abnormal proteins in the brain -- hallmarks of Alzheimer’s disease.

Visceral fat refers to the accumulation of fat around internal organs such as the liver, heart, kidneys, and the mesentery of the intestine. Unlike subcutaneous fat, which lies beneath the skin, visceral fat is metabolically active and poses greater health risks.

The study, presented at the ongoing annual meeting of the Radiological Society of North America (RSNA), showed that visceral fat can predict the risk of Alzheimer’s up to 20 years before the earliest symptoms of dementia appear.

The study included 80 cognitively normal midlife individuals (average age: 49.4 years), of which about 57.5 per cent were obese, and the average body mass index (BMI) of the participants was 32.31.

Researchers from the Washington University School of Medicine in St. Louis, Missouri examined the association of BMI, visceral fat, subcutaneous fat, liver fat fraction, thigh fat, and muscle, as well as insulin resistance and HDL (good cholesterol), with amyloid and tau deposition in Alzheimer’s disease.

A higher level of visceral fat was related to increased amyloid -- accounting for 77 per cent of the effect of high BMI on amyloid accumulation.

Other types of fat did not explain obesity-related increased Alzheimer’s pathology, the team said.

“Our study showed that higher visceral fat was associated with higher PET levels of the two hallmark pathologic proteins of Alzheimer’s disease -- amyloid and tau,” said lead study author Mahsa Dolatshahi, post-doctoral research associate at Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis, Missouri.

The study also showed that higher insulin resistance and lower HDL were associated with high amyloid in the brain. The effects of visceral fat on amyloid pathology were partially reduced in people with higher HDL.

The team urged for lifestyle modifications to reduce belly fat and cut down the development of Alzheimer’s disease.

“This study goes beyond using BMI to characterize body fat more accurately with MRI and, in so doing, reveals key insights about why obesity can increase risk for Alzheimer’s disease,” Dr. Dolatshahi said.