Obesity and the influence of genes

People with low copy number of the salivary amylase gene (AMY1) have increased risk of being obese.

A lot has been said and done when it comes to obesity and diets. There is still the stigma that people are overweight because they want to, because they don't exercise or eat way beyond their daily needs. What if the cause is different from what we acknowledge?

There have been studies comparing effects of low-carbohydrate diets with low-fat diets, diabetic versus non-diabetic people, studies in men and in women and pretty much whatever we can think of.

The new research sets the difference because it focused on how the body manages the digestion of carbohydrates, instead of analyzing the brain and appetite. This study is about genes and copy number variants (CNVs), particularly of the salivary amylase gene (AMY1). The salivary amylase is the most abundant enzyme in our saliva and it breaks down starch into sugar, initiating digestion from the moment food is inserted in our mouths.

Authors found that low AMY1 copy number was associated with impaired levels of salivary amylase gene expression and the correspondent protein. These results were also associated with enlarged risk of obesity. On the other hand, the more copies of AMY1 within one's genome, the less probability of increased body mass index (BMI) and obesity.

“The 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.”

The study was performed primarily in an European population (about 5500 subjects) and afterwards in a Singapore population (about 700 subjects) in order to confirm that the obtained results were not Europe-confined.

Professor Philippe Froguel, one of the lead authors on the study, said: “I think this is an important discovery because it suggests that how we digest starch and how the end products from the digestion of complex carbohydrates behave in the gut could be important factors in the risk of obesity. (...) .”

Cover image: Photobucket.

References

DOI: 10.1038/ng.2939

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