Although it was thought that obesity was largely due to overeating and lack of exercise, researchers now think that genetics play a crucial role in whether fat is stored or used up as energy.
People with higher ratios of weight to height often carry a variant of the FTO gene, nicknamed “the obesity gene”.
The US researchers have discovered that the obesity gene switches on two other genes which stop fat being burned up as heat.
And, they have shown that it is possible to turn off those genes using a gene editing technique that snips out bad DNA code and replaces it with the preferred sequence.
The scientists believe the technique could prevent or even cure obesity in those people with the faulty gene and negate the effects of a high-fat diet.
“Obesity has traditionally been seen as the result of an imbalance between the amount of food we eat and how much we exercise, but this view ignores the contribution of genetics to each individual’s metabolism,” said researcher Manolis Kellis, of MIT.
“By manipulating [the genetic code] we could switch between energy storage [in the form of fat] and energy dissipation, providing new hope for a cure for obesity.”
About a third of Britons are expected to be obese by 2030 and more than half by 2050. The proportion was fewer than 3% in the 1970s.
Weight gain is a risk factor for many health problems, including diabetes, heart disease, stroke and some cancers.
Researchers gathered fat samples from Europeans and found that in people with the variant FTO gene one letter of DNA code had been replaced by another. The wrong code was causing genes IRX3 and IRX5 to turn on when they should have been off.
Previous studies have shown that IRX3 and IRX5 switch on during times of fat loss in the body, such as during periods of starvation, to conserve fat.
Researchers used a new technology to edit the DNA code and repair the sequence in mice and human cells. A modified protein was injected into the body to snip away specific sections of DNA. Mice that had been bred to be obese lost weight.