Obesity can be linked to an increased risk of dementia.
British researchers used data on 6,582 men and women aged 50 and over who were cognitively healthy at the start of the study. The analysis in the International Journal of Epidemiology tracked the population for an average of 11 years and recorded incidents of doctor-diagnosed dementia.
Almost 7 percent of the group developed dementia. Compared to people of normal weight (body mass index between 18.5 and 24.9), overweight people with a B.M.I. from 25 to 29.9, 27 percent were more likely to have dementia and obesity with a B.M.I. of 30 or higher, 31 percent were more likely to have dementia.
The researchers also found that women with central obesity – a waist size larger than 34.6 inches – were 39 percent more likely to develop dementia than women with a normal waist size. Middle fat was not associated with a higher risk of dementia in men.
The study controlled age, gender, APOE4 (a gene known to increase your risk of Alzheimer's, the most common type of dementia), education, marital status, smoking, and other known dementia risks.
The lead author, Yixuan Ma, a student at University College London, said that this observational study did not prove cause and effect.
"Obesity is just a risk," she said. "It doesn't mean that an obese person necessarily gets dementia. But there are many reasons why it is good to maintain a normal weight and do intense physical activity for a lifetime."