Popular Science plunges into a study in The Lancet examining the possible neurological benefit of being obese:
The team of British researchers looked at records of almost two million patients with an average age of 55. The data has been collected since 1992, and the researchers correlated patients’ body mass index (BMI) with diagnosis of dementia. They found that people who were underweight had a 35 percent higher risk of developing dementia than people of normal weight, and people who were very obese (with a BMI greater than 40 kg/m2) were 29 percent less likely to be diagnosed with the condition than people of normal weight.
The reason why the obese are less likely to develop dementia is still unknown, though the researchers hypothesize that the obese may be absorbing more of particular kinds of vitamins or nutrients that could stave off the condition.
The researchers were surprised by the results because their work overturns the conclusions of several previous studies, the most recent of which was published in 2008.