That sinfully delicious banana split you eat may provide instant gratification, but it could rob you of memories down the road.

New research suggests that the more calories and fat a person consumes, the greater the risk of developing Alzheimer's disease. But the finding, published today in The Archives of Neurology, holds true only for those who are genetically predisposed to dementia.

José Luchsinger, an epidemiologist at the Taub Institute for Research of Alzheimer's Disease and the Aging Brain at Columbia University in New York, said a low-calorie diet may decrease the death of nerve cells and boost production of nerve-protecting factors.

To conduct the research, Dr. Luchsinger and his colleagues looked at 980 people over 65 who took part in a long-term study on aging. At the outset, none of the subjects showed signs of dementia; after four years, 242 had developed Alzheimer's disease.

Among those with Alzheimer's, 68 per cent tested positive for the presence of apolipoprotein E epsilon 4 allele, a gene that has been associated with the disease. It is believed the gene facilitates the buildup of plaque in the brain that characterizes Alzheimer's.

Scientists divided those with the gene into four groups, based on their caloric consumption. People in the group with the highest calorie intake were 2.3 times as likely to develop Alzheimer's than those in the group who ate the least.

There was no correlation between caloric consumption and dementia in people without the APOE epsilon 4 gene.

Dr. Luchsinger said the research suggests that "susceptible individuals" (those with the gene) should consider a low-fat, low-calorie diet as a way of delaying the onset of possible symptoms of dementia.

It is well-established that people with Alzheimer's change their diets markedly when symptoms of dementia begin. They tend to dramatically cut protein and increase consumption of sweets; the disease makes them crave empty calories.

Almost 300,000 Canadians have Alzheimer's disease or a related dementia. That translates into 1 in 13 people over the age of 65 and 1 in 3 Canadians over the age of 85.