Researchers here find yet another reason to avoid becoming overweight, in that the brains of people who are overweight tend to lose white matter at an accelerated rate. The mechanism involved remains to be determined, but based on past research, the greater levels of chronic inflammation produced by larger amounts of visceral fat tissue would seem to be a good place to start looking.
Our brains naturally shrink with age, but scientists are increasingly recognising that obesity - already linked to conditions such as diabetes, cancer and heart disease - may also affect the onset and progression of brain ageing; however, direct studies to support this link are lacking. In a cross-sectional study - in other words, a study that looks at data from individuals at one point in time - researchers looked at the impact of obesity on brain structure across the adult lifespan to investigate whether obesity was associated with brain changes characteristic of ageing. The team studied data from 473 individuals between the ages of 20 and 87.
The researchers divided the data into two categories based on weight: lean and overweight. They found striking differences in the volume of white matter in the brains of overweight individuals compared with those of their leaner counterparts. Overweight individuals had a widespread reduction in white matter compared to lean people. The team then calculated how white matter volume related to age across the two groups. They discovered that an overweight person at, say, 50 years old had a comparable white matter volume to a lean person aged 60 years, implying a difference in brain age of 10 years. Strikingly, however, the researchers only observed these differences from middle-age onwards, suggesting that our brains may be particularly vulnerable during this period of ageing.
Despite the clear differences in the volume of white matter between lean and overweight individuals, the researchers found no connection between being overweight or obese and an individual's cognitive abilities, as measured using a standard test similar to an IQ test. "We don't yet know the implications of these changes in brain structure. Clearly, this must be a starting point for us to explore in more depth the effects of weight, diet and exercise on the brain and memory."