Overeating blamed on genes

21 October, 2007

This one may eliminate a lot of guilt feelings for those inclined to overeating. A recent research has revealed that people who cannot help eating too much are doing so mainly because of their genes.

A study conducted in the United States has found that 50% of the population carries a gene variation that may give them extra pleasure from eating. This could mean that some people are willing to work twice as hard for snacks as others.

The ‘overeating-inducing’ gene affects dopamine, an important message-carrying chemical, or neurotransmitter, associated with behavior and movement.

Dr Jennifer Temple, a neuroscientist at the University at Buffalo in New York, who worked on the study, said this gene is not only associated with
overeating but has also been associated with drug addiction, alcohol abuse, and gambling. It is associated with decisions on ‘food as reward,’ too.

In an article in the journal Behavioral Neuroscience, Dr Jennifer Temple and colleagues described an experiment in which they gave people access to many tasty snacks, including chips and chocolate.

The volunteers thought they were just taste-testing the food, but the research team was watching to see who ate the most.

The researchers also ran genetic tests on their 74 volunteers, looking for variations in two genes that affect dopamine levels.

One gene appeared to have no effect on eating. But the ‘Taq1 A1’ variation of the gene had a perceptible effect.

Each person carries two copies of each gene – one inherited from the mother and one from the father. Nearly half the population has one A1 and one A2 version, while the other half has two copies of A2. It is rare for someone to have two A1s.

People with two A2s experience feelings of reward easily, while people with A1 may have to work harder to feel good, according to the researchers.

Dr Jennifer Temple’s team did a simple test to see who would work the hardest for snacks: a computer test in which they had to click a mouse. People could win points they could trade for treats, and could quit at any time.

People who had the A1 variation and who were obese worked twice as hard to get the food as people who were either not obese or who were obese and did not have the gene.

The finding, according to Dr Jennifer Temple, may help explain why so many people will continue to eat even when they are not hungry. However, she adds that not everyone may choose food as reward.

The team plans to conduct more studies to see whether some people get more of a reward from gambling or drugs.

It also found evidence that chemically manipulating dopamine levels alters eating behavior, which may help in the development of better diet drugs.