A study done published by Neurology followed the health of 6000 British people over a decade, all were between 35 to 55 years of age. 

To measure their cognitive ability they took cognitive skills tests three times every year for the duration of the study.

From the study a link was made between a growing waistline and a decline in cognitive ability. The people who were obese showed a much more rapid decline in their skills compared to those who are not considered obese. 

The researchers are clear that they were only looking at decline in cognitive function and not dementia. Although the line between the two is somewhat blurred not all who experience cognitive decline go on to have dementia.

One problem with the study was that all participants were from one area of society, the Civil Service, so the results may not apply to the population as a whole. 

They say more research is needed into the connection between the two, and Shirley Cramer of Alzheimer’s Research UK says that as obesity levels are rising it is important that we understand the relationship between the two better. 

Original article can be found here: http://www.bbc.co.uk/news/health-19323061