New research in the journal Nature Genetics suggests that there may be a genetic link between the way carbohydrates are digested and obesity.
"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," first author Dr. Mario Falchi says.
"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," he adds.
The focus of Dr. Falchi's research is a gene called AMY1, which regulates an enzyme called salivary amylase present in human saliva.
Salivary amylase is the first enzyme to encounter food when it enters our mouths, beginning a process of starch digestion that is continued in the gut.
The number of copies of a gene that a person carries can vary throughout their DNA, although people usually have two copies of each gene. The researchers found that the number of copies of AMY1, however, can vary wildly between people.
The study found that people with a low number of copies of AMY1 were most likely to become obese.
The researchers examined the number of copies of AMY1 present in the DNA of more than 6,000 people from the UK, France, Sweden and Singapore. According to the results of the study, people with a low number of copies of AMY1 were most likely to become obese.
The researchers arrived at these results by comparing pairs of siblings where one was obese and the other was a healthy weight.
From this data, they found that AMY1 was the gene that had the greatest influence on body weight. They then counted the number of times the gene was repeated in each individual and how this affected their obesity risk.
Results provide 'an important discovery'
Co-author Dr. Julia El-Sayed Moustafa considers this study to be "novel in that it identifies a genetic variation that is both common and has a relatively large effect on the risk of obesity in the general population. The number of copies of the salivary amylase gene is highly variable between people, and so, given this finding, can potentially have a large impact on our individual risk of obesity."
"I think this is an important discovery," says Prof. Philippe Froguel, another study author, "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."
Prof Froguel concludes:
"Future research is needed to understand whether or not altering the digestion of starchy food might improve someone's ability to lose weight, or prevent a person from becoming obese. We are also interested in whether there is a link between this genetic variation and people's risk of other metabolic disorders such as diabetes, as people with a low number of copies of the salivary amylase gene may also be glucose intolerant."
Other recent studies have also tackled the genetic components of obesity. Medical News Today reported on a study by researchers from the University of Leicester in the UK, who investigated a link between methylation of the gene HIF3A and changes in weight.