Feb. 3, 2010 -- Missing genes may be behind at least some cases of morbid or extreme obesity, according to a new study.
Researchers found that a small but significant portion of morbidly obese people are missing a section of their DNA that may contribute to their obesity.
The results suggest around seven in every 1,000 morbidly obese people are missing this section of their DNA, which contains about 30 genes. This genetic variation was not found in any people of normal weight.
"Although the recent rise in obesity in the developed world is down to an unhealthy environment, with an abundance of unhealthy food and many people taking very little exercise, the difference in the way people respond to this environment is often genetic," says researcher Philippe Froguel, of the School of Public Health at Imperial College London, in a news release.
Overall, researchers say about one in 20 cases of morbidly obese people is caused by genetics, including previously identified genetic mutations and these missing genes. But many more genetic mutations linked to obesity are yet to be found.
The researchers hope that identifying genetic variations that cause people to be morbidly obese will lead to the development of genetic tests that can help determine the best treatment.
"If we can identify these individuals through genetic testing, we can then offer them appropriate support and medical interventions, such as the option of weight loss surgery, to improve their long-term health," says Froguel.
In the study, published in Nature, researchers first identified the missing genes in teenagers and adults who had learning difficulties or delayed development.
The results showed 31 people had nearly identical deletions in one copy of their DNA. All of the adults with this genetic variation had a BMI of over 30, which means they were obese.
People inherit two copies of their DNA, one copy from their mother and one from their father. Sometimes one copy of one or more genes is missing and can affect a person’s development, as shown by this study.
In the second part of the study, researchers examined the genomes or genetic maps of 16,053 European people who were either obese or normal weight. They found 19 more people with the same set of missing genes. All of these individuals were morbidly obese.
Researchers did not find the genetic deletion in any normal-weight people. Although they do not know the function of the missing genes, previous studies suggest some of them may be involved with delayed development, autism, and schizophrenia.