Are you envious of your friends who seem to eat whatever they want without gaining a pound, while a single slice of pizza causes you to gain several? Genetics may be related to the difference, according to a new report.

» RELATED: How to lose weight: Take a break from your diet for two weeks 

Researchers from Duke University and the University of North Carolina at Chapel Hill recently conducted an experiment, published in the Proceedings of the National Academy of Sciences journal, to target mutations in a gene called ankyrin-B, which is associated with weight gain among heavier people.

To do so, they engineered mice that had human variants of ankyrin-B. They found the mice grew quicker and faster than mice without the gene, even when getting the same amount of exercise and nutrition.

"We call it fault-free obesity," senior author Vann Bennett said in a statement. "We believe this gene might have helped our ancestors store energy in times of famine. In current times, where food is plentiful, ankyrin-B variants could be fueling the obesity epidemic."

»RELATED: Why this diet praised by Jennifer Aniston could work for you

Why is that?

They discover these rodents stored calories in fat tissues as opposed to the other tissues that burn the calories and use them as energy. This causes the glucose to produce even more fat, which is unusual. Normally, a special membrane works as a door to keep the glucose from spreading to other cells, but the mutation keeps the “flood gates opened.”

"We found that mice can become obese without eating more, and that there is an underlying cellular mechanism to explain that weight gain," Bennett said. "This gene could enable us to identify at-risk individuals who should watch what kind of calories they eat and exercise more in order to keep their body weight under control."

For future studies, researchers hope to identify humans with the gene to determine how it could affect other variants of health.

»RELATED: Lose the belly pooch: 7 do’s and don’ts to accomplish a flat stomach