( Health.com ) -- If you 're genetically predisposed to be overweight , the amount of sleep you get each night could make a big difference in how influential those genes are , a new study suggests . After analyzing the sleep habits and body weight of 1,088 pairs of twins , including genetically identical ones , researchers concluded that people who get plenty of sleep -- at least nine hours per night -- have more control over their weight through their behavior than people who sleep less . Among twins who slept less than seven hours per night , genes accounted for 70 % of the differences in body mass index ( BMI ) , while so-called environmental factors , such as diet and exercise habits , were responsible for just 4 % of the differences . The pattern was reversed among twins who slept nine or more hours per night . In this group , environmental factors accounted for 51 % of BMI differences and genes accounted for just 32 % . Health.com : How much sleep do you really need ? Getting adequate sleep , in other words , appears to dampen genetic risk and allow the influence of diet , exercise , and other controllable lifestyle factors to `` surface , '' the researchers say . `` The less you sleep , the more important genetic factors are to how much you weigh , '' says lead author Nathaniel F. Watson , M.D. , co-director of the University of Washington Medicine Sleep Center , in Seattle . `` The longer you sleep , the greater the influence of environmental factors like meal composition and timing . '' Previous research has found that too little sleep is associated with a higher BMI , but many of those studies have n't been able to entirely rule out the possibility that genes , or complicating factors such as sleep disorders , are partly responsible for the link . Twin studies , by contrast , allow researchers to tease out the complex relationship between genes and environment . Identical twins share the exact same DNA , so most differences in weight can be attributed to environment rather than genes . And fraternal twins , though genetically dissimilar , tend to share the same background and risk factors . ( All of the twins in the study , both identical and fraternal , were raised in the same household . ) Health.com : 7 tips for the best sleep ever . The new study , which appears in the journal SLEEP , suggests that `` the amount of sleep you get has an effect on your gene expression , '' says Michael Weissberg , M.D. , a sleep specialist and professor of psychiatry at the University of Colorado School of Medicine , in Denver . Researchers have identified more than 20 genes that are linked to obesity risk through their effects on appetite , blood sugar ( glucose ) metabolism , and other channels , but it 's not clear which specific genes were at play in the study . `` Based on previous research , it 's probably related to glucose metabolism , metabolism in general , inflammation -- all pathways that we already know are associated with obesity , '' Watson says . Health.com : Surprising health benefits of sleep . Sleep deprivation puts stress on your body , and that stress could help explain the relationship between sleep and gene expression seen in the study , says Carl Boethel , M.D. , director of the Sleep Institute at Scott & White Healthcare , in Temple , Texas . `` When you are constantly depriving yourself of sleep , you are keeping yourself in a state of stress , and the genes that encode for that stressful environment start saying , ' I need to hold on to calories , ' '' Boethel says . The study does n't answer the question of whether you can `` sleep yourself thin , '' Watson says , but it does highlight the importance of adequate sleep to overall health . `` We spend so much time in this country trying to keep our weight down with diet and exercise , but we never think about sleep , '' he says . `` I think of sleep as the third leg on the stool of good health , along with diet and exercise . '' Copyright Health Magazine 2011 .
Researchers analyzed the sleep habits and body weight of 1,088 pairs of twins . Genes accounted for 80 % of BMI ##s in twins who slept less than seven hours . More research allows for environmental factors like exercise and diet to surface .