Fat people are less intelligent than individuals with a healthy weight, a provocative study has claimed. The theory is likely to prove controversial as the weight loss campaigners argue that reasons behind weight problems may vary from one individual to another.
The research suggests overweight men and women have less grey and white matter in key areas of the brain. They also have greater impulsiveness and 'altered reward processing' and hence no mental capacity to control their poor diet choices. Two-thirds of men and 57 per of women in Britain are categorised as being overweight or obese, the highest such rates in Europe. Some 26 per cent of boys and 29 per cent of girls are overweight or obese, compared to 17.5 per cent and 21 per cent in 1980.
‘Obese people have less grey and white matter in key areas of the brain, causing greater impulsiveness, which lowers their mental capacity and leads to poor diet and lifestyle choices.’
The research involved 32 adults - 16 men and 16 women - from the US city of Baltimore in Maryland, whose brain images were studied. Anyone with a history of brain damage, substance abuse or mental illness was excluded from the group. The researchers measured the body mass index (BMI) which is a measure that adults can use to see if they are a healthy weight for their size and body fat percentages and compared them to differences in brain structure and function.
Outlining the object of the study, the authors said "It has been suggested that body composition itself might somehow affect the neural systems that underlie cognition, motivation, self-control and salience processing, which would in turn affect one's ability to make better lifestyle choices, forgoing immediate and/or highly salient rewards for the sake of longer-term health and wellness goals."
Lead researcher Chase Figley, an assistant professor in the Department of Radiology at the University of Manitoba, said the brain scans covered changes across the whole organ but main focus was on 'specific networks'. In particular he was interested in the 'salience network' which he described as the seat of motivation, willpower, and the ability to persevere through physical and emotional challenges.
Professor Figley said, "It stands to reason that these changes could further affect the ability of overweight individuals to exert self-control and maintain healthy lifestyle choices." He added "There are previous studies that imply elevated body fat can cause these sorts of brain changes."
The study was reported in the journal Frontiers in Neuroscience
showed there was no significant different in terms of white matter distribution between people who had a normal weight and people who were fat. But people with a higher BMI actually had slightly more grey matter. A closer look at the 'salience network' revealed that heavier and fatter people had less white matter in the salience network. There were also differences in the dorsal striatum, an area of the brain involved with habitual behaviour.