An international study claims to have finally found the reason as to why some people who eat a high-fat diet remain slim, while others pile on the weight -- obesity is determined by brain.

The study, led by Monash University, found that a high-fat diet causes brain cells to become insulated from the body preventing vital signals, which tell the body to stop eating and burn energy, from reaching the brain efficiently.

Prof Michael Cowley, who led the study, said there were two clear outcomes from the findings.

“We discovered that a high-fat diet caused brain cells to become insulated from the body, rendering the cells unable to detect signals of fullness to stop eating. Secondly, the insulation also created a further complication in that the body was unable to detect signals to increase energy use and burn off calories,” he said.

The study showed that support cells in the brain developed overgrowth in a high-fat diet. This prevented the regular brain cells from connecting with other neural mechanisms, which determine appetite and energy expenditure.

Prof Cowley said the study findings provide a critical link in addressing the obesity epidemic.

“These neuronal circuits regulate eating behaviours and energy expenditure and are a naturally occurring process in the brain. The circuits begin to form early in life so that people may have a tendency towards obesity even before they eat their first meal,” he said.

Eating a high fat diet causes more “insulation” in the nerve cells, and makes it even harder for the brain to help a person lose weight.

“Obese people are not necessarily lacking willpower.

Their brains do not know how full or how much fat they have stored, so the brain does not tell the body to stop refuelling. Subsequently, their body’s ability to lose weight is significantly reduced,” Prof Cowley said.

For their study, the researchers monitored the eating and body composition of groups of rodents for four months and found those with a neural predisposition to obesity gained 30 per cent more weight compared to six per cent of the group with obesity resistant cells.

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