Is obesity 'all in the mind?'Eating the same diet has different effect on weight because of brain wiring
How is it that two people can lead the same lifestyle and follow the same diet, but one ends up slim and the other overweight?
Usually put down to vague statements about "metabolism", this paradox has long puzzled scientists. But now a new study suggests that the difference is related to the individual's brain, and how it responds to feelings of fullness when eating.
Researchers at Yale School of Medicine analyzed the effects of a high-fat, high-calorie diet on groups of rats that had been bred to ensure their vulnerability to diet-induced obesity was known beforehand.
The study found that the rats that became obese already had a significant difference in the feeding centre of the brain - neurons that are supposed to signal when you've eaten enough and when to burn calories are much more sluggish in these animals because they are inhibited by other cells. But rats that were more resistant to obesity had much more active signalling in the brain, which made them stop eating more quickly.
Study leader Tamas Horvath said: "It appears that this base wiring of the brain is a determinant of one's vulnerability to develop obesity - these observations add to the argument that it is less about personal will that makes a difference in becoming obese, and it is more related to the connections that emerge in our brain during development."
Animals who became obese also suffered from a brain inflammation which was absent in the other rats. "This emerging inflammatory response in the brain may also explain why those who once developed obesity have a harder time losing weight," Dr Horvath said.
Although the study seems to suggest that long term weight is fixed by genetic heritage, Dr Horvath cautions that more work needs to be done on this matter.
"Specifically, the emerging view is that besides genetics, maternal impact on the developing brain is likely to be critical to imprint these feeding circuits, thereby determining one's vulnerability or resistance to obesity," Dr Horvath said.
The study was reported in the Proceedings of the National Academy of Sciences.
This article was published on Tue 3 August 2010
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