Sleeping for longer duration may not increase your weight, says a new study published in the journal Sleep.

According to the study shorter duration of sleep might actually increase your BMI, as the genetic factors are more likely to be expressed when you are sleep deprived.

"The results suggest that shorter sleep provides a more permissive environment for the expression of obesity related genes, or it may be that extended sleep is protective by suppressing expression of obesity genes,” said Dr Nathaniel Watson of the University of Washington, the lead author of the study.

For this study, the researchers looked at more than 1,088 pairs of twins and found that longer sleep duration was associated with lower BMI. Heritability of BMI was twice as high for people who slept less than what it was for people who slept more.

In another study published in the journal Obesity, short sleep duration was found to be independently associated with weight gain among all age groups. Another study too links reduced sleep with modest weight gain in women.

Shorter duration of sleep makes people eat more, especially food that is high in fat. When people do not get enough exercise to use this extra food, they tend to store it in their bodies, according to a study published in the American Journal of Clinical Nutrition.

In the latest study that describes how longer sleep might influence genetic factors, researchers found that genetic factors accounted to 70 percent for weight variations in twins who got an average of 7 hours of sleep. The genetic influence was just 38 percent in twins who slept for 9 hours or more.

The study suggests that behavioral factors like eating healthy and exercising regularly might deter the genetic pre-disposition of gaining weight. The authors say that this is a preliminary investigation.

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