Sept. 20, 2022 -- Night owls may be more prone to diabetes and heart disease than early birds because their bodies don’t burn fat for energy as efficiently, according to a new study in Experimental Physiology.

People who wake up early tend to rely more on fat as an energy source and are often more active during the day, the researchers found. Those who stay up later may not expend as much energy, which means fat may build up on their bodies and increase the risks for diabetes and heart disease.

“This could help medical professionals consider another behavioral factor contributing to disease risk,” Steven Malin, PhD, one of the study authors and a metabolism specialist at Rutgers University, told The Guardian.

“Night owls are reported to have a higher risk of obesity, type 2 diabetes, and cardiovascular disease when compared with early birds,” he said.

Malin and colleagues split 51 obese middle-aged adults into early birds and night owls, depending on how they answered a questionnaire about sleep and activity habits. The researchers monitored the participants’ activity patterns for a week and tested their bodies’ fuel preferences at rest and while performing moderate-intensity or high-intensity exercise on a treadmill.

The research team found that early birds were more sensitive to insulin levels and burned more fat than night owls while at rest and during exercise. On the other hand, the night owls were less sensitive to insulin and burned more carbohydrates rather than fat as an energy source.

It’s unclear why the metabolism differences exist between early birds and night owls, Malin said. But one aspect could be a mismatch between their natural body cycles and the actual times that people go to sleep and wake up.

“A potential explanation is they become misaligned with their circadian rhythm for various reasons, but most notably among adults would be work,” he said.

For instance, a night owl may prefer to go to bed late but still need to wake up early to go to work or look after children. This could force them out of alignment with their circadian rhythm.

The study findings could have implications for sleep-wake patterns, including the health risks of nightshift work and annual time change policies, USA Today reported.

“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 attenuate these is an area we hope becomes clear in time.”

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Experimental Physiology: “Early chronotype with metabolic syndrome favors resting and exercise fat oxidation in relation to insulin-stimulated non-oxidative glucose disposal.”

USA Today: “Night owls may be more prone to heart disease and diabetes, study finds.”

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