|Cheese: Food alone does|
not cause obesity
Contrary to popular perception, obesity is not due to environmental factors alone. Genes are important, Dr Sadaf Farooqi of the University of Cambridge in England, told a medical conference on Friday.
She however said it would take a while to figure out how genes exactly caused obesity. It would be a complicated process.
As many as 50-70 genes are thought to be involved in making people obese, with some playing a more important role than others.
Farooqi and her colleagues have identified three single genetic mutations that cause obesity.
She said genetic defects may be involved in about one to two percent of cases of common severe obesity. In children, who are severely obese from an early age, genes could be the cause in six percent of such cases.
But she added that very little is understood about why people become obese or why certain ethnic groups are, to different degrees, predisposed to gain weight.
"We know that genes are important based on our studies because if you are completely lacking certain important genes that is enough to cause severe obesity," she said.
Farooqi and her team are 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.
Only five families worldwide, four in Britain and one in Turkey, have been identified with the mutation.
By giving the children leptin injection which releases signals to the part of the brain that co-ordinates eating behaviour, Farooqi and her team have helped them control their appetite. Their weights have also reduced to normal levels with no serious side effects.
Other children had different and more common single genetic defects that cause obesity.
This showed for the first time that a small change in a gene is enough to determine how much food one eats in a single meal. Genes control eating behaviour, said Farooqi, who presented her findings to the 12th European Congress on Obesity.
Although these genes affect only a small number of people, the research allows scientists to begin to understand what is going on. Its relevance to obesity, though complex, might also be revealed.