Metabolic differences between early birds and night owls could help predict diabetes and heart disease risk

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 aerobic fitness levels than night owls. On the other hand, “night owls” (people who prefer to be active later in the day and at night) use less fat for energy at rest and during exercise.

Researchers from Rutgers University, New Jersey, USA ranked the participants (not=51) into two groups (early and late) based on their “chronotype” – our 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 birds 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.

The differences in fat metabolism between “early risers” and “night owls” show that our body’s circadian rhythm (wake/sleep cycle) might affect how our body uses insulin. A sensitive or impaired ability to respond to the hormone insulin has major implications for our health. This observation advances our understanding of the impact of our body’s circadian rhythms on our health. Since chronotype appears 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 fit better 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.

Steven Malin, lead author, professor, Rutgers University, New Jersey, USA


The physiological society

Journal reference:

Malin, Sask., et al. (2022) Early chronotype with metabolic syndrome promotes fat oxidation during rest and exercise over insulin-stimulated nonoxidative glucose disposal. Experimental Physiology.

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