Early risers rely more on fat as an energy source and are often more active during the day than those who stay up later, meaning fat may accumulate more easily in night owls, the scientists found. The findings may explain why night owls are at greater risk for type 2 diabetes and cardiovascular disease, and may help doctors identify early patients who are more likely to develop the conditions. “This could help medical professionals look at another behavioral factor that contributes to disease risk,” said Professor Steven Malin, the study’s senior author and a metabolomist at Rutgers University in New Jersey. The researchers divided 51 obese middle-aged adults into early birds and night owls based on their answers to a questionnaire about sleep and activity habits. They tracked the volunteers’ activity patterns for a week and tested their body’s fuel preferences at rest and while performing moderate- or high-intensity exercise on a treadmill. Writing in Experimental Physiology, the team describes how early birds were more sensitive to blood levels of the hormone insulin and burned more fat than nocturnals when at rest and during exercise. The night owls were less sensitive to insulin and their bodies preferred carbohydrates over fat as an energy source. Malin said it was unclear why differences in metabolism were seen in nightbirds and early birds, but one possibility, he believes, is a mismatch between the time people go to bed and wake up the next morning and the circadian rhythms that govern their clocks. their body. “Night owls are reported to have a higher risk of obesity, type 2 diabetes and cardiovascular disease compared to early birds,” he said. “One possible explanation is that they are out of alignment with their circadian rhythm for a variety of reasons, but the most common among adults would be work.” If a person is an owl, Malin added, they may prefer to go to bed late but have to get up early to go to work or take care of the kids, and that can cause them to fall out of alignment with their body clocks. . when they would rather sleep. The findings could influence discussions about the health risks of night work and even changing clocks to match the hours of the day. “If we promote a timing pattern that is out of sync with nature, it could exacerbate health risks,” Malin said. “Whether dietary patterns or activity can help with mitigation is an area we hope will become clear over time.”
