The authors explained that prior studies had demonstrated a link between sleep and bodyweight. This study differs in that the researchers focused on what impact sleep has on genetics, and ultimately body weight.
Lead author, Nathaniel Watson, a neurologist, and team set out to determine whether how long people slept might modify genetic and environmental influences on BMI (body mass index). They gathered self-reported data from 604 identical twins (monozygotic twins), plus 484 fraternal twins (dizygotic twins) from the University of Washington Twin Registry. 66% of them were women, and their average age was 36.6 years.
The participants had given information on their sleep patterns, weight and height.
According to the authors, sleep duration was defined as:
- Short sleep - less than 7 hours per night
- Normal sleep - between 7 and 8.9 hours per night
- Long sleep - at least nine hours per night
The authors found that:
- The participants who slept longer each night were slimmer than those who slept less.
- Participants with short sleep duration had a higher genetic risk of a greater BMI
- For those sleeping over nine hours per night, genetic factors accounted for approximately 34% of variations in weight
- For participants sleeping less than 7 hours each night, genetic factors accounted for about 70% of variations in weight
- For participant sleeping between 7 to 9 hours each night, genetic factors accounted for about 60% of variations in weight
The more we sleep, the less our genes drive weight gain
Watson explained that BMI and sleep are both inherited features. However, they noticed that the variations observed in how much the twins in their study weighed, was based on their sleep duration.
The researchers said that scientists are not yet sure which genetic pathways are impacted by sleep. They suspect they must include those that drive metabolism, fat storage, hunger, satiety, and some other psychological functions.
In an Abstract in the same journal, the authors concluded:
"Shorter sleep duration is associated with increased BMI and increased genetic influences on BMI, suggesting that shorter sleep duration increases expression of genetic risks for high body weight. At the same time, longer sleep duration may suppress genetic influences on body weight. Future research aiming to identify specific genotypes for BMI may benefit by considering the moderating role of sleep duration."