By John Messmer, MD

Everyone has seen people who seem to eat and eat and never gain weight. Alternatively, some people can't seem to lose weight on any diet. Some might say that their entire family is heavy so it must be genetic. If only we could blame our genes, maybe we could just relax and eat without guilt and accept our weight. News reports of the possible existence of just such a gene have raised hopes that a treatment for obesity might be in the near future and that perhaps it is not really our fault two-thirds of us are overweight or obese.

The skinny gene: Adipose

The gene, named "adipose," was discovered in fruit flies about 50 years ago when Winifred Doane, now an emeritus professor at Arizona State University, was studying fruit flies that were particularly thin. Recent obesity research on the Human Genome Project led to rediscovery of the work. There are hundreds of genes that have effects on weight according to an article by Rankinen, et al. in an April 2006 issue of Obesity, but the adipose gene is different. It is apparently a normal part of our genome rather than a mutation. When it works efficiently, people and other organisms accumulate less fat. However, no one understands why it works more efficiently in some people and not others.

What can we blame our weight gain on? 

Unfortunately, we can't blame our weight on the lack of a skinny gene. Despite the existence of a gene for thinness, scientists acknowledge that obesity happens through a combination of genetic, environmental, and behavioral contributors. Not all people with efficient adipose genes are thin and not all people who are overweight have less active adipose genes. Anyone who regularly eats more than he burns off will gain weight and anyone who eats less, will lose it.

What is the normal female body type?

The fact is, our genes do not make us obese. There are a range of body types that are normal when all the genetic material is working properly. The normal female body, for example, is heavier than the typical model that the media would have us think is the ideal. Actually, the average female figure is probably closer to the shape seen in ancient statues with some women tending to be a bit heavier and some a bit lighter. Having a little extra body fat would have conferred a survival advantage against famine in the days before supermarkets and supersized portions.

Bottom line: avoid overeating

Some people are more efficient at storing fat, but most "naturally thin" people eat less than their heavier counterparts or burn off more calories. So, even if some way of giving everyone efficient adipose genes is found, people will still have to avoid overeating to maintain a normal weight.

Everything else being equal, some people will be thin, some average, and some will have fuller figures due to genetic differences. Except for genetic mutations and certain medical syndromes, no one can say their genes make them fat.