Can you blame weight gain on your genes?

New research from Imperial College London indicates that obesity in the general population may be genetically linked to how our bodies digest carbohydrates.

Body weight, genes and carbs

The study investigated the relationship between body weight and a gene called AMY1, which is responsible for an enzyme present in our saliva known as salivary amylase. This enzyme is the first to be encountered by food when it enters the mouth, and it begins the process of starch digestion that then continues in the gut.

People usually have two copies of each gene, but in some regions of our DNA there can be variability in the number of copies a person carries. It is believed that higher numbers of copies of the salivary amylase gene have evolved in response to a shift towards diets containing more starch since prehistoric times.

Researchers looked at the number of copies of the gene AMY1 present in the DNA of thousands of people from the UK, France, Sweden and Singapore. They found that people who carried a low number of copies of the salivary amylase gene were at greater risk of obesity.

Obesity could be in the genes

The chance of being obese for people with fewer than four copies of the AMY1 gene was approximately eight times higher than in those with more than nine copies of this gene.

People who carried a low number of copies of the salivary amylase gene were at greater risk of obesity.[/su_pullquote]

Researchers estimated that with every additional copy of the salivary amylase gene there was approximately a 20 per cent decrease in the odds of becoming obese.

"Previous genetic studies investigating obesity have tended to identify variations in genes that act in the brain and often result in differences in appetite, whereas our finding is related to how the body physically handles digestion of carbohydrates. We are now starting to develop a clearer picture of a combination of genetic factors affecting psychological and metabolic processes that contribute to people's chances of becoming obese. This should ultimately help us to find better ways of tackling obesity,” said Dr Mario Falchi, also from Imperial's School of Public Health and first author of the study.

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