Monday, September 17, 2007

What has diabetes to do with body fat?

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Genes seem to play an important role, challenging the value of weight loss to prevent diabetes. One of these genes, the adiponectin gene SNP276, has been linked to diabetes and obesity in a Taiwanese study with more than a thousand elderly persons. This gene determines different variants of the hormone adiponectin, produced by body fat cells. Adiponectin lowers the risk of diabetes and heart attacks. But some adiponectin variants are better than others. The variant (allele) G is considerably better than variant T. The highest risk of diabetes and of obesity has been found in persons with the combination TT, that is, having got the bad variant of the gene from both mother and father.

The bad variant seems to be a common cause of a higher diabetes risk as well as a tendency to accumulate more body fat. Both outcomes can be linked to the gene, but of course other factors like the amount of consumed food and the physical activity must also be taken into account. The study authors conclude:

"Genetic variation of the adiponectin gene is associated with obesity (...) and diabetes mellitus in the elderly. The genetic effect on diabetes mellitus is partially independent of BMI."
When diabetes is partially independent of body mass index, weight loss will be partially useless in the fight against diabetes.

And what about the other part?

But genes cannot explain the whole story. There is still one part of diabetes that may be linked to body mass index, regardless of the genes. But this study does not allow any conclusion about causes, because neither food nor physical activity have been taken into account. Thus, not even the non-genetic rest of a link between body fat and diabetes is in favour of weight loss.

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