Gene sequence puts half of UK population at greater risk of obesity, researchers say
· Discovery could suggest ways to curb epidemic
· Problem most common in Indian-origin Britons
- The Guardian,
- Monday May 5 2008
A section of genetic code that puts half the population at greater risk of obesity, diabetes and heart disease has been discovered by scientists who say those carrying the sequence are on average 2kg (4.4lb) heavier than others, with 2cm larger waistlines and a tendency to become resistant to insulin and vulnerable to late-onset diabetes.
While 50% of the UK population carries the obesity-related sequence, it is a third more common among people of Indian Asian ancestry than among Europeans, the scientists said.
The finding raises hopes of new measures to curb the soaring obesity rates, including genetic screening programmes to identify children most at risk of what has become one of the leading causes of poor health and mortality in the developed world.
"A better understanding of the genes behind problems such as diabetes and cardiovascular disease means that we will be in a good position to identify people whose genetic inheritance makes them most susceptible," said Professor Jaspal Kooner, lead author of the study at Imperial College London. "We can't change their genetic inheritance, but we can focus on preventative measures, including lifestyle factors such as diet and exercise."
By unravelling the genetics of obesity, scientists believe that ultimately they will be able to develop therapies for the condition.
Obesity rates in Britain have almost quadrupled in the past 25 years, making the country the most obese in Europe. More than one in five men and a quarter of women in Britain are now clinically obese. Each year, an estimated 30,000 people in England alone die prematurely from obesity-related conditions such as diabetes, heart disease and cancer.
The research was carried out as part of the London Life Sciences Population project into the environmental and genetic causes of obesity, diabetes and heart disease. To find the gene sequence, scientists analysed the genetic makeup of 30,000 British citizens of European and Indian Asian ancestry and looked for markers that were common only among those with obesity.
The section of genetic code lies close to a gene called MC4R, which is know to control energy levels in the body by regulating how much food we eat and how much energy we burn. The team believe the gene sequence controls the activity of the MC4R gene, which has previously been linked to rare and extreme cases of childhood obesity.
"Until now, we have understood remarkably little about the genetic component of common problems linked with obesity, such as cardiovascular disease and diabetes. Finding such a close association between a genetic sequence and significant physical effects is very important, especially when the sequence is found in half the population," Kooner said.
The discovery that the gene sequence is more common among people of Indian Asian ancestry could explain the unusually high rates of obesity and insulin resistance in this group, which makes up 25% of the world's population but is expected to account for 40% of global heart disease by 2020.
Last year, scientists reported that people who inherited a particular form of a gene called FTO were 70% more likely to be obese than those who did not. Like MC4R, the FTO gene is thought to influence appetite and how much energy the body uses.
Taken together, the FTO variant and MC4R gene sequence increase body weight by 4-5kg.
In a second paper, researchers from Oxford University and the Wellcome Trust's Sanger Institute in Cambridge also link a gene sequence close to MC4R with obesity. Their study, based on 90,000 people in Sweden, found that those inheriting the section of DNA were 1.5kg heavier than others.
The study, led by Inês Barroso, at the Sanger Institute, found a dramatic difference between the effect the obesity genes had in childhood and adulthood. Between the ages of four and seven, children gained almost twice as much weight as adults, almost entirely by developing more fat, the scientists found.
"The precise role in obesity of genetic variants in FTO and near MC4R remains to be discovered, but we can now begin to understand the biological consequences of these," Barroso said.
Alan Johnson, the health secretary, described obesity as "the most significant public and personal health problem facing our society" when he unveiled the government's five-point plan for tackling the country's weight problem earlier this year.
The government's strategy aims to encourage healthier lifestyles by raising awareness of nutrition, such as the advice to eat five portions of fruit and vegetables a day, and by promoting daily physical activity.
Under the plans, junk food has been banned from school vending machines, and cookery classes are due to be made compulsory in a majority of schools in September. The government is also considering clamping down on the construction of fast-food outlets close to schools and parks.
Another strand of the strategy aims to help people cut their intake of saturated fats, salt and sugar, a move that could see the food industry come under pressure to adopt single food labelling systems. The plans include talks with the entertainment industry to find ways for parents to limit how much time children spend watching TV and playing computer games.