67 researchers found that the likelihood of obesity
increased by 80% for each hour of lost sleep. Although, sleep disturbances were not directly
related to obesity; they were negatively correlated with level of physical activity, suggesting
that sleep disturbances could indirectly impact body weight through a reduction in physical
activity. On the other hand, no relationship between level of physical activity and sleep
duration was found. Similarly, in a study of European adolescents, investigators found that
short sleep duration was associated with obesity, increased food intake, and sedentary habits,
but not with level of physical activity.68 But not all the emerging evidence supports a
relationship between short sleep duration and increased BMI; some studies have found no
association between sleep duration and BMI,69-73 while others have found a U-shaped
relationship with the odds rising for those with shorter and longer sleep duration