Putting on a bit of weight lowers dementia risk

Researchers have found that slightly overweight elderly men fare better than their slimmer counterparts who are more likely to develop dementia later in life.

The study, led by University of Western Australia, has shown that elderly men who are considered overweight have a lower chance of developing dementia than those within the normal weight range.

The study followed more than 12,000 men aged 65-84 years during 1996-2009. It aimed to determine if being overweight later in life increases the incidence of dementia.

The researchers say the results were unexpected as there is good evidence that overweight or obese younger adults have an increased risk of cognitive decline as they get older.

"When we designed this study this is not something that we were expecting to find. We were expecting to find the opposite, that obesity would increase the risk of dementia," said Prof Osvaldo Almeida, who led the study.

According to the researchers, one possible explanation is survivorship bias, where people who are overweight later in life are unusually healthy compared with normal weight people in the same age group.

Another explanation is physiological changes as people age, causing body to protect itself from degenerative effects.

"The fat tissue behaves a little like an endocrine organ and releases a number of substances into the bloodstream that have different actions on the body.

"In animal studies we know that leptin, which is one of the substances that fat tissues produce, seems to have a neuro-protective effect on the hippocampus which is an area of the brain where cells are important for memory," Almeida said.