You can blame it on the holidays, a bad breakup or even a slow metabolism, but new research shows that gaining weight may actually be all in your genes.

According to results published in the journal Nature, there are more than 100 locations across the genome that play roles in various obesity traits. These genetic tendencies can one day possibly help doctors develop better weight-loss therapies for their patients that don't just include diet and exercise.

"Our work clearly shows that predisposition to obesity and increased body mass index is not due to a single gene or genetic change," senior study author Elizabeth Speliotes, with the University of Michigan Health System, said in a statement.

"The large number of genes makes it less likely that one solution to beat obesity will work for everyone and opens the door to possible ways we could use genetic clues to help defeat obesity," she added.

During the study, researchers measured the body mass index (BMI) of nearly 340,000 people, and compared it with their genetic makeup. In all, they found 97 sites associated with obesity - that's three times more than scientists had previously estimated.

It is well known that obesity can lead to all sorts of metabolic conditions, particularly type 2 diabetes and high cholesterol. Fat buildup around the abdomen - creating the infamous "muffin top" or "beer belly" - increases the risk of cardiovascular diseases specifically.

"If we can figure out which genes influence where fat is deposited, it could help us understand the biology that leads to various health conditions, such as insulin resistance/diabetes, metabolic syndrome, and heart disease," explained researcher Karen Mohlke, who worked on a related study.

The researchers also note that while some genes involved in obesity could already have been implicated in other aspects of human health, others could be part of pathways that are not yet understood. Scientists still have a long way to go before they fully understand the link between the human genome and obesity, but further research hopefully will show how these genes play a part in various diseases.

"A major challenge now is learning about the function of these genetic variations and how they indeed increase people's susceptibility to gain weight," senior author Ruth Loos added. "This will be the critical next step, which will require input from scientists with a range of expertise, before our new findings can be used towards targeted obesity prevention or treatment strategies."

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