Genes key to understanding obesity

June 3, 2003 in Nutrition Topics in the News

Genes key to understanding obesity

Changes in diet and a sedentary lifestyle have fueled an obesity epidemic, but genetics also play a role and could explain why some people put on weight more easily than others, a leading obesity expert said last week.

Dr. Sadaf Farooqi, of the University of Cambridge in England says "for most of us, how genes work is going to be complicated and take a while to figure out. But genes influence how we respond to the environment."

As many as 50-70 genes are thought to be involved in obesity, with some playing a more important role than others. The researchers have identified three single genetic mutations that cause obesity. She said genetic defects are thought to be involved in about one to two percent of cases of common severe obesity, and up to six percent of cases in children who are severely obese from an early age.

But very little is understood about why people become obese or why certain ethnic groups are predisposed to gain weight to different degrees.

The team is treating 900 severely obese children with genetic mutations that have caused their illness. Several of the children have a very rare genetic defect that causes a deficiency in the hormone leptin. By giving the children injections of leptin, which releases signals to the part of the brain that co-ordinates eating behavior, the team have helped them control their appetite and reduce their weight to normal levels with no serious side effects. Other children had different and more common single genetic defects that cause obesity.

This shows for the first time that a single change in a gene is enough to determine how much food you eat in a single meal. Genes control our feeding behavior.

Although these genes affect only a small number of people, the research allows scientists to begin to understand what is going on and to see how relevant it is to common obesity, where the role of genes is expected to be much more complex.

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