If French scientists are to be believed being obese is linked to a decline in a person's cognitive function.
In other words they say being overweight lowers your intelligence.
We already know that being very overweight has implications for blood pressure and the heart, and can shorten a person's life quite considerably; to hear also that it can affect a person's intelligence is almost too much and will be viewed by many as dubious.
The news is opportune as just last week government figures illustrated that Britain is now the "fat man" of Europe, with nearly a quarter of adults and more than 14 per cent of children under 16 classified as obese.
The five-year study of 2,223 healthy adults by Toulouse University claims to have found a link between obesity and the decline in a person's mental ability, and involved men and women aged between 32 and 62.
They were given four mental ability tests consisting of word-list learning (four recalls), a Digit–Symbol Substitution Test, and a selective attention test, repeated five years apart.
Medical, psychosocial, and environmental information was collected in 1996 and in 2001.
The researchers say they found that people with a Body Mass Index of 20 or less could recall 56 per cent of words in a vocabulary test, while those who were obese, with a BMI of 30 or higher, could remember only 44 per cent.
What is more the overweight people also showed a higher rate of cognitive decline when they were retested five years later with their recall decreasing to 37.5 per cent, whereas those with a healthy weight retained their level of recall.
British guidelines suggest a person with a BMI of between 18.5 and 25 is considered to be at an ideal weight, while 25 is overweight and 30 or more is regarded as clinically obese.
Lead study author Dr. Maxime Cournot suggests that hormones secreted from fats could have a damaging effect on cerebral cells, resulting in decreased brain function.
She also suggests that as obesity is a widely known cardiovascular risk factor, due to the thickening and hardening of the blood vessels, the same possibly happens with the arteries in the brain.
Dr. Cournot is an assistant professor in clinical epidemiology at Toulouse University Hospital.
The researchers say that even after adjustment for age, sex, educational level, blood pressure, diabetes, and other psychosocial co-variables were made, a higher BMI was associated with a higher cognitive decline.
The research is published in this month's Neurology journal.