A rare genetic mutation linked to severe obesity has been identified by researchers who conducted experiments in mice and genetic analyses of people.
The team at Boston Children's Hospital found that mice with the genetic mutation gained weight even though they ate the same amount of food as mice without the mutation. The gene appears to be involved in regulating metabolism and food consumption, the researchers said.
According to a report on the discovery in The New York Times, only one person — a severely obese child — has been found to have a mutation in the same gene that completely disables it. But the discovery of the same effect in mice and in the child — reported this week in the journal Science — may help explain why some people put on weight easily while others eat all they want and seem never to gain an ounce.
It may also offer clues to a puzzle in the field of obesity: Why do studies find that people gain different amounts of weight while overeating by the same amount?
Scientists have long believed genes play a role in obesity. As researchers developed tools to look for the actual genes, they found evidence that many — maybe even hundreds — of genes may be involved, stoking appetites, making people voraciously hungry.
For the study, researchers conducted genetic analyses of 500 people around the world. They found mutations in the human equivalent of a gene known as Mrap2 in four people with severe, early onset obesity. Each of the four patients had only one copy of the mutation.
The finding suggests that these rare mutations might directly cause obesity in less than 1 percent of obese people. But other mutations in the MRAP2 gene may be more common and might interact with other mutations and environmental factors to cause more common forms of obesity, the study authors said.
Further investigation into how these mutations work may improve knowledge about the body's mechanisms for energy storage and use, the researchers noted in a news release.
"The history of obesity for many many years has been one of blaming people for lack of self control," lead investigator Joseph Majzoub, M.D., chief of endocrinology at Boston Children's, told The New York Times. "If some of it is due to a slow metabolism, that would completely change the perspectives of parents and patients. It really would change the way we think of the disease."