A five-year study of more than 2,000 middle-aged people in France has found a possible link between weight and brain function.

Research published in Neurology, the journal of the American Academy of Neurology, found that people with a higher Body Mass Index (BMI) scored lower on average in cognitive tests within a sample.

The research led by Dr Maxime Cournot, of Toulouse University Hospital in France, used 2,223 healthy people aged 32 to 62 who sat four cognitive tests including word learning in 1996 and again in 2001.

Results from a word memory test showed that people with a BMI of 20 — considered to be a healthy level — remembered an average of nine out of 16 words. Meanwhile, people with a BMI of 30 — inside the obese range — remembered an average of just seven out of 16 words.