Adding more evidence to theories linking DNA to weight, European scientists report that a genetic variation seems to virtually guarantee that a person will become obese.
The genetic variation in question robs people of about 30 genes and appears to be found in seven of every 1 000 severely obese people, the researchers report. The same variation also may be linked to mental retardation and learning disabilities.
"Obesity is definitively a genetic trait, and it is very likely that additional small chromosomal abnormalities exist that may dramatically increase the risk of obesity and may also be linked to brain developmental problems," said Dr Philippe Froguel, co-author of a study published in the February 4 issue of the journal Nature and head of genomic medicine at Imperial College London.
In the new study, researchers examined the genes of teens and adults who had learning difficulties and developmental delays. Thirty-one people were missing the genes in question, and all were obese.
The researchers then looked at the genomes of 16 053 people who were either of normal weight or obese. Nineteen people had the same genetic deletion, and all were severely obese.
"We feel that this is a major advance - the first paper to convincingly demonstrate that a relatively rare genetic variant can also be an important cause of common obesity," said study co-author Alexandra Blakemore, a senior lecturer at Imperial College London.
"Although the percentage of severely obese people with this (variation) is just under one person, that adds up to an awful lot of people in total," Blakemore said. "The effect on carriers is very strong."
Enzyme or protein
But what are the missing genes doing to the body to make people become obese? That remains to be determined.
"The mechanism by which this genetic defect unveils itself may give us insight into how other conditions lead to obesity. There may be an enzyme or a protein that is involved in the development of obesity," said Dr Stuart Weiss, an assistant clinical professor at NYU Langone Medical Centre, who is familiar with the study findings.
Finding the cause "will allow us to investigate medications and therapies" that could turn something in the body on or off, he said.
Not all obese people can get skinnier by eating less and exercising more, Weiss said.
"The bottom line is that they may be able to eat less, but their bodies may be so efficient that they can extract calories from food much more effectively and may not be burning energy as efficiently as others," he said.
This fact leads to unhappy news for some obese people, he said. "If you're eating just one pea and you're gaining weight, you'll have to cut the pea in half."
Still, the future could bring genetic tests for patients that could allow doctors to tailor treatments to their particular bodies, he added. - (HealthDay News, February 2010)