Announced on Friday at the British Science Festival, the study found that a diet rich in saturated fats leads to damage to the brain's hypothalamus, a key region involved in controlling appetite. The findings suggest that saturated fats may have a direct impact on the body's ability to stick to a diet, said Lynda Williams of the Rowett Institute for Nutrition and Health at Aberdeen University.

"The hypothalamus is a small area at the base of the brain containing neurones that control the amount of food we eat and the energy we expend," she explains. "However, this control breaks down in obesity, the system appears not to work, and we don't really know why this happens."

 "To help answer the question we used a strain of mice that is susceptible to weight gain and put half of them on a high-fat diet and the other half on a normal low-fat diet," she says.

"In our study we found that genes and proteins changed in response to a high fat diet and that these changes are normally associated with damage in the brain, indicating that damage had occurred in the hypothalamus in mice that ate a diet high in saturated fat," she states.

While more research needs to be done, Williams (and health advocates) warns against a high fat diet over a protracted period, but not worrying over an occasional unhealthy treat. "The key is to avoid excessive weight gain and to eat sensibly in the first place," she advises. "We all deserve a treat now and then."

A separate study released in January found that people who consumed diets high in trans fats were more likely to have brain shrinkage and scored lower on thinking and memory tests, compared to people who followed a healthy diet, low in trans fats and high in vitamins.