Sleeping at least seven hours a night may help people eat less sugar, according to a new study in the American Journal of Clinical Nutrition. The research also found that getting more shuteye was an attainable goal for healthy adults who typically got less than the recommended amount, and that simple strategies like reducing screen time before bed and avoiding coffee late in the day really did help.
Researchers at King’s College London wanted to see whether it was possible to successfully extend sleep duration in “short sleepers” with just a short one-time intervention. To find out, they designed a randomized controlled trial: First, they recruited 42 healthy adults who reported regularly sleeping between 5 and 7 hours a night, and asked them to wear sleep trackers and keep food and sleep diaries for one week.
Half of the volunteers then participated in a 45-minute sleep consultation with a sleep psychologist, which aimed to extend their time in bed by up to an hour and a half per night. The people in the study were counseled on why sleep is important, and each received a recommended bedtime along with a list of at least four behaviors—personalized to their lifestyle—they should try to adopt over the next few weeks.
Those behaviors included avoiding caffeine and electronic devices before bed, establishing a relaxing bedtime routine and not going to bed full or hungry.
The remaining volunteers did not receive a consultation and were told to go about their normal behaviors and keep their regular schedules. Both groups were then followed for four weeks. During the last week of the study, they again wore sleep tracking devices and kept sleep and food diaries.
The sleep intervention worked, at least for those four weeks: Of the people who received counseling, 86% increased their average time spent in bed. Half also increased their average time asleep, with increases ranging from 52 to 88 minutes. Among the people who did not receive a consultation, there were no significant changes.
The researchers also analyzed people’s food diaries to see if increased sleep could affect diet and nutrient intake. They found that people who extended their sleep patterns consumed, on average, 10 grams fewer added sugars per day at the end of the study, compared to the beginning. The numbers also suggested that those who slept longer consumed fewer fats and total carbohydrates as well, although those findings were not as strong.
When it came to changes in weight, body composition, cholesterol or blood glucose levels, there were no significant changes between the two study groups. But that may be because the study only lasted four weeks, says lead author Wendy Hall, a researcher in the department of nutritional sciences.
“The intervention period was relatively short, so the next step is to test whether body weight and body fat percentage would also be lowered following an intervention lasting months, rather than weeks,” Hall said in an email. Still, she calls the reduction in added sugars “exciting and potentially important.”
Hall also notes that the study involved a young, healthy group of adults. “We may find more exaggerated effects in groups at risk for heart disease and diabetes,” she says, especially since lack of sleep is a risk factor for these and other chronic conditions.
This isn’t the first study to suggest that more time in bed may lead to healthier eating. But it’s significant in that it shows how easy, low-cost strategies can really make a difference, says Hall. “Most participants found that limiting technology use from back-lit screen devices close to bedtime, keeping technology devices outside of the bedroom, maintaining regular bedtimes and wake times, and avoiding caffeine later in the day were among the more applicable practices they could apply to their current lifestyle,” she says.
The study did suggest, however, that increased sleep didn’t necessarily mean better sleep. While the sleep consultations improved sleep duration for several people in the study, they also resulted in a slight decrease in overall sleep quality—possibly because an adjustment period is needed for the body to get used to any changes, says Hall.
Larger and longer studies are needed to further test this type of sleep intervention and its effects on sugar intake and other dietary measures, says Hall. But she’s optimistic with her team’s findings so far. “It is notoriously difficult to change people’s health behaviors, and the important thing about our study is that we have established that it is possible to successfully increase time in bed and also sleep duration,” she says.