Tuesday, March 23, 2010

Cute, chubby, and doomed?

Cute, cuddly, and ..... catastrophic? That may be the case regarding babies, if the latest hot-news bulletin is to be believed. As early as in utero, babies may become prone to obesity that can have later health consequences. Of course, under normal conditions chubby babies are likely to be resilient, able to call on an energy reserve. But in our current society perhaps this not just predisposes to later obesity, but according to this particular study could predispose to lifelong obesity. The issue is important to those who think that eating habits can be set in school. But school may be too late.

There are lots of issues at play here. One, however, is particular important when it comes to the GWAS religion: the idea that meaningful risk for complex traits can be based on genotypes. Part of the evidence is the widespread observation that most traits (and obesity is one) have substantial heritability--that is, substantial resemblance among relatives. That suggests genetic causation.

But if chubby mothers, or mothers' eating habits, affect their fetuses, then not only may this predispose the little darlings to a hefty lifetime, but it could also induce resemblance among relatives. That will be interpreted as being due to genes, when in fact it could be the inheritance of lifestyle effects. There's a big difference. And if this is important, it further weakens the case for GWAS and the relentless pursuit of genes as the important factors to understand in major public health research.

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