by Carol A. Westbrook
Are you pleasantly plump? Rubinesque? Chubby? Weight-challenged? Or, to state it bluntly, just plain fat? Have you spent a lifetime being nagged to stop eating, start exercising and lose some weight? Have you been accused of lack of willpower, laziness, watching too much TV, overeating and compulsive behavior? If you are among the 55% of Americans who are overweight, take heart. You now have an excuse: blame it on your genes.
It seems obvious that obesity runs in families; fat people have fat children, who produce fat grandchildren. Scientific studies as early as the 1980's suggested that there was more to it than merely being overfed by fat, over-eating parents; the work suggested that fat families may be that way because they have genes in common. Dr. Albert J Stunkard, a pioneering researcher at the University of Pennsylvania who died this year, did much of this early work. Stunkard showed that the weight of adopted children was closer to that of their biologic parents than of their adoptive parents. Another of his studies investigated twins, and found that identical twins–those that had the same genes–had very similar levels of obesity, whereas the similarity between non-identical twins was no greater than that between their non-twin siblings. It was pretty clear to scientists by this time that there was likely to be one or more genes that determined your level of obesity.
In spite of the compelling evidence, it has been difficult to identify the actual genes that cause us to be overweight. This is due partly to the fact that lifestyle and environment are such strong influences on our weight that they can obscure the genetic effects, making it difficult to dissociate genetic from environmental effects. But the main reason it has been difficult to find the fat gene is because there is probably not just one gene for obesity, as is the case for other diseases such as ALS (Lou Gehrig's disease). There seem to be many forms of obesity, determined by an as yet unknown number of genes, so finding an individual gene is like looking for a needle in a haystack.