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Is staying up late bad for you? New research suggests night owls may have a higher risk of heart disease and diabetes

September 20, 2022, 3:00 PM UTC
Man in bed on laptop while woman is sleeping.
Our sleep cycles could affect how our bodies use insulin.
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It’s long been said that the early bird gets the worm, and new research shows they may have other advantages as well. According to a study published in Experimental Physiology, our activity patterns and sleep cycles can impact our risk for Type 2 diabetes and heart disease.

Researchers out of Rutgers University in New Jersey found that “night owls,” defined as people who prefer to be active later in the day and night, have a reduced ability to use fat for energy compared to “early birds,” or people who prefer to be active in the morning. As a result, this fat buildup can increase risk of diseases. 

Study participants were split into two groups based on their chronotype, or inclination to sleep at certain times of the day, and advanced imaging was used to measure body mass, body composition and insulin sensitivity, while breath samples were used to determine fat and carbohydrate metabolism, according to a press release about the study. Participants’ daily activity patterns were monitored and they were given a controlled diet to lessen dietary influence on the results.  

Early birds were found to use “more fat for energy at both rest and during exercise than night owls, the study says” They were also found to be more sensitive to insulin, whereas night owls were found to be insulin resistant, which means “their bodies require more insulin to lower blood glucose levels, and their bodies favored carbohydrates as an energy source over fats.” Meanwhile, the cause for the shift in metabolic preference is unknown at this time and requires further research.

“The differences in fat metabolism between ‘early birds’ and ‘night owls’ shows that our body’s circadian rhythm (wake/sleep cycle) could affect how our bodies use insulin. A sensitive or impaired ability to respond to the insulin hormone has major implications for our health,” study author and Rutgers professor Steven Malin says in the release. “This observation advances our understanding of how our body’s circadian rhythms impact our health. Because chronotype appears to impact our metabolism and hormone action, we suggest that chronotype could be used as a factor to predict an individual’s disease risk.”

Research also found that early birds are “more physically active and have higher fitness levels than night owls who are more sedentary throughout the day,” says Malin. However, additional research is needed to determine whether exercising earlier in the day has greater health benefits than working out at night.