The discovery of a 'fat gene' could lead to the 'danger' of obese people giving up trying to lose weight, experts have warned.
It could mean obese people will simply blame the gene for struggling with their weight - rather than eating properly and exercising.
New research has found a common gene, named FTO, found in millions of Britons could be largely responsible for exploding rates of obesity. People with two copies of the gene are almost 70% more at risk of being obese than those having none, and three kilograms heavier on average.
The new findings, which estimates 16% of the population has the gene, is the first research to identify a common, population-wide genetic link to obesity.
Although the gene mutation only accounts for a modest weight increase, scientists believe it can tip the scales and lead to obesity in an already heavy population. By 2010 a third of all men and 28% of women in England will be obese, according to figures from the Department of Health.
Tam Fry, board member of the National Obesity Forum, which advises the Government on the issue, said the new research should not stop obese people trying to loose weight. "There is a huge danger," he said.
"The danger is that the announcement is likely to cause people to shrug their shoulders and say, 'OK, that's it. I have got a bad gene, I will just get fatter and fatter.' That is good information, that they have got the gene, but it is really important it should spur them further to keep their weight as much in check as possible."
Obesity rates in England have more than tripled since the 1980s. Around one in five adults are obese and more than half either obese or overweight - almost 24 million people.
Obesity is defined by a Body Mass Index (BMI), a measurement relating weight and height, of 30 and over. People who are overweight have a BMI that is between 25 and 30. Obesity greatly increases the risk of heart disease and diabetes, and has also been linked with cancer. Each year it causes tens of thousands of premature deaths and costs the country an estimated Ł7 billion.
The obesity gene was identified by a study led by scientists from the Peninsula Medical School in Exeter and the University of Oxford. DNA samples from more than 38,500 people from across the UK and Finland showed a strong association between a particular variation of a gene called FTO and obesity. Genes come in pairs, and individuals carrying one copy of the FTO mutation were found to have a 30% higher risk of being obese than those with no copies.