Scientists Debunk So-Called 'Fat Gene'

Jan. 18, 2007 — -- Just as death and taxes are inevitable, some people assume they're also fated to be fat.

Overweight parents tend to have overweight children, but is DNA or diet the culprit? Is it nature or is it nachos?

It's true that we can't pick our parents, we can't change our genes. Most of us are not hard-wired to become obese, though, suggests a new study published today in the New England Journal of Medicine.

So, while you may be having a hard time fitting into your favorite jeans, it's unlikely that your genes are to blame.

A team of British scientists examined 300 people who became severely obese at a young age, to determine whether a faulty gene was involved. Researchers were looking specifically at the gene in charge of the leptin receptor.

Leptin is a hormone that controls appetite and can influence how much we feel like eating. It has been previously implicated in animal obesity studies.

Scientists examined the obese study participants to see whether this so-called obesity gene was disturbed in any way. They found that only 3 percent of people had an abnormal leptin gene -- indicating that leptin is probably not a factor for most obese people.

The same group of scientists behind today's report were actually the first to find human subjects with a defective leptin gene, nearly 10 years ago.

In the earlier study, they identified a leptin deficiency in two obese children from the same Pakistani family. The children lost significant amounts of weight following leptin injections.

The finding, combined with the previous animal studies, seemed to set off a firestorm of "leptinomania," so to speak.

Leptin -- derived from the Greek word "leptos," meaning thin -- continues to be touted by some supplement sellers and diet-book authors as a cure for obesity. Today's report, though, suggests leptin probably won't work any magic.

Janet Helm is a registered dietitian and freelance nutrition writer in Chicago.