‘Night owls’ may have a higher risk of type 2 diabetes and heart disease than ‘early risers’

Are you an early riser or a night owl? Our activity patterns and sleep cycles could influence our risk of diseases, such as type 2 diabetes and heart disease. New research published in Experimental physiology discovered that sleep/wake cycles cause metabolic differences and alter our body’s preference for energy sources. Researchers have found that those who stay up late have a reduced ability to use fat for energy, which means fat can build up in the body and increase the risk of type 2 diabetes and other diseases. cardiovascular.

Metabolic differences relate to each group’s ability to use insulin to promote glucose uptake by cells for energy storage and utilization. “Early risers” (people who prefer to be active in the morning) rely more on fat for energy and are more active during the day with higher levels of aerobic capacity than “night owls” (people who prefer to be active later in the day and at night). On the other hand, night owls use less fat for energy at rest and during exercise.

Researchers from Rutgers University, New Jersey, USA, categorized the participants (n=51) into two groups (early and late) based on their “chronotype” – the natural propensity to seek activity and sleep at different times. They used advanced imaging to assess body mass and body composition, as well as insulin sensitivity and breath samples to measure fat and carbohydrate metabolism.

The participants were followed for a week to assess their activity patterns throughout the day. They followed a calorie and nutrition controlled diet and had to fast overnight to minimize dietary impact on results. To study energy preference, they were tested at rest before performing two 15-minute exercise sessions: a moderate-intensity session and a high-intensity session on a treadmill. Aerobic fitness levels were tested through an incline challenge where the incline was increased by 2.5% every two minutes until the participant reached a point of exhaustion.

The researchers found that early risers used more fat for energy at rest and during exercise than night owls. Early risers were also more insulin sensitive. Night owls, on the other hand, are insulin resistant, meaning their bodies need more insulin to lower blood sugar, and their bodies prioritize carbohydrates for energy over fat. The impaired ability of this group to respond to insulin to promote fuel consumption may be harmful as it indicates an increased risk of type 2 diabetes and/or heart disease. The cause of this shift in metabolic preference between early birds and night owls is still unknown and requires further investigation.

Lead author Professor Steven Malin of Rutgers University said: “The differences in fat metabolism between ‘early birds’ and ‘night owls’ show that our body’s circadian rhythm (wake cycle /sleep) could affect the way our body uses insulin. The ability to respond to the hormone insulin has major implications for our health. This observation allows us to better understand the impact of the circadian rhythms of our body on our health. Since chronotype seems to impact our metabolism and hormonal action, we suggest that chronotype could be used as a factor. to predict an individual’s risk of disease.

“We also found that early risers are more physically active and have higher fitness levels than night owls who are more sedentary throughout the day. Further research is needed to examine the link between chronotype, exercise, and metabolic adaptation to determine if exercising earlier in the day has greater health benefits. »

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