Sleep plays a vital role in maintaining both physical and mental health and while most of us feel we get enough hours, the time we got to bed may also impact wellbeing.
New research published in Experimental Physiology compared the health of those who have later bed times and early risers and found significant differences. Researchers found the wake/sleep cycles causes metabolic differences, further impacting the body's preference for energy sources.
People who go to bed later were found to use less fat for energy, meaning lipids may build up within the body, raising the risk for Type 2 diabetes and heart disease. Academics from Rutgers University in New Jersey, USA, divided participants into two groups: either the early or the late sleepers.
Participants were monitored for a week to assess their activity patterns across the day, with both groups eating a calorie and nutrition controlled diet. Researchers used advanced imaging to assess body mass and body composition, as well as insulin sensitivity and breath samples to measure fat and carbohydrate metabolism, reports the Mirror.
Sleep's impact on weight
The metabolic rates and differences relate to how well a person can use insulin to promote glucose uptake by the cells for storage and energy use, a vital component in healthy weight.
People who are early birds rely more on fat as an energy source and are more active during the day. On the other hand, night owls use less fat for energy at rest and during exercise.
Night owls were also found to be more insulin-resistant, meaning their bodies requires more insulin to lower blood glucose levels, and their bodies favoured carbohydrates as an energy source over fats.
Previous research has found that people who fall asleep after midnight had a 25% higher risk of developing heart and circulatory disease.
“Getting enough sleep is important for our general wellbeing as well as our heart and circulatory health, and most adults should aim for seven to nine hours of sleep per night," added Regina Giblin, British Heart Foundation's senior cardiac nurse.
Sleep's impact on energy levels
“We also found that early birds are more physically active and have higher fitness levels than night owls who are more sedentary throughout the day,” said Professor Steven Malin at Rutgers University, senior author of the study.
“Further research is needed to examine the link between chronotype, exercise and metabolic adaptation to identify whether exercising earlier in the day has greater health benefits.
"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.”
If a person has a sensitive or impaired ability to efficiently respond to insulin, major health implications will be evident, further warned Prof Malin.
"This observation advances our understanding of how our body's circadian rhythms impact our health,” he added.
“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.”
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