Friday, 13 April 2007

The FTO gene and obesity

The HYS page on the BBC news page made me laugh out loud, not least because some of the 'fattist' comments were quite funny. The obesity gene story is nicely summarised on the Wellcome site.

Its not surprising that the media coverage has (deliberately) set out to exploit the 'nature OR nurture' aspects of the story. After all, the same debate raged in Psychology for much of the last fifty years. That said, it is a flawed argument. Genes (DNA) can only operate in conjunction with the environment, and to pretend otherwise is naive. But the argument makes for good telly and chat blogs.

I'm interested that the gene frequencies are so high: 1 in 6 have one copy of the FTO gene (or allele). That is very high for a gene that potentially causes so much harm.

The allele frequencies in the population often reflect natural selection in the past. For much of the last 30 000 years we have lived on the edge of starvation, and any alleles that promoted eating or the conversion of food into storage products would be at an advantage and be selected for by evolution. This probably why the FTO allele is so frequent now. (Similar arguments are used for the levels of the cystic fibrosis allele and for sickle cell anaemia allele. In these cases two copies of the allele are harmful and can cause disease.)

What is new in our evolution is our ability to eat large quantities of energy and nutrient-rich foods. Since it has been an evolutionary advantage in the past to eat as much as we can, it is hard to break this habit today.

We are, at the end of the day, still hunter gatherers exploiting our territories for whatever we can get from them.

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