THURSDAY, Sept. 30, 2004 (HealthDayNews) -- Mutations in the gene that regulates body weight have a significant impact on obesity, says a German study in the current issue of the Journal of Medical Genetics.
There are up to 34 mutations in the melanocortin-4 receptor gene (MC4R), but they're rare. It's estimated that only 2 percent to 3 percent of very obese people have MC4R gene mutations.
In this study, researchers compared the body weights of 181 relatives from 25 families of severely obese people who carried MC4R mutations. They found that carriers of these mutations had a much higher BMI -- a formula used to calculate appropriate weight for height -- than those without the mutations.
The impact of these mutations on weight was twice as great for women as for men.
Second-degree relatives of obese people without MC4R mutations had much lower rates of obesity than first-degree relatives. But that difference was much less obvious among relatives of obese people who carried an MC4R mutation, the study found.
The researchers concluded that MC4R mutations entail a strong disposition to obesity but do not, by themselves, account for obesity.
The U.S. National Heart, Lung, and Blood Institute has a BMI chart.