A new report which collates health data from almost 2 million people advances the idea that those who are obese or overweight in their middle years may be less likely to contract dementia than people who are of a normal weight or underweight. Those with excess or excessive body fat were found to be approximately 30 percent less likely to see the onset of dementia 15 years after people with a conventionally-considered healthy weight. On the other hand, those who live their life in an underweight condition were more likely (by a substantial 34 percent) to display symptoms of dementia than people with normal weight.

Dementia is an umbrella term for a number of brain diseases, including Alzheimer’s, which display a decreased ability to think and remember. Other symptoms can include language problems, emotional difficulties and malaise.[1][2] A person’s consciousness is not affected.

Such findings were unexpected, said Dr. Nawab Qizilbash, the lead researcher involved  the study “BMI and dementia: feast or famine for the brain?” published in The Lancet: Diabetes & Endocrinology. Qizilbash is employed by OXON Epidemiology Ltd. in Madrid. OXON Epidemiology is a private consulting firm that conducts studies and science on behalf of big pharmaceutical companies.

The study does not show an actual cause-and-effect relationship between being overweight and lower dementia rates. Instead, it only indicates that an association exists.

The same study, Qizilbash pointed out, confirmed what so many before it have declared: The rate of premature death increases from being overweight or obese. His point was that individuals should not use his preliminary conclusions as a license to gain weight. “You may not live long enough to get the benefit,” he said, even if such a protective benefit does exist.

Although no biological explanation has been identified to account for the association, Qizilbash believes his findings could lead to new dementia treatments.