Whether you are a night owl or an early bird influences your risk of type 2 diabetes and heart disease.
People who sleep late and are active later in the day are more likely to develop type 2 diabetes and heart disease than those who wake up early.
A person’s chronotype has an impact on a number of diseases such as metabolic syndrome (a condition that increases the risk of type 2 diabetes, cardiovascular disease, and stroke).
Chronotype is related to circadian rhythms and is the body’s natural tendency to sleep or stay alert over a 24-hour period.
Early chronotypes are those individuals who prefer to get up early and do their activity in the morning, whereas late chronotypes are those who stay up late and are active later in the day.
A study suggests that our body metabolism and preferred source of energy are influenced by the sleep–wake cycle.
Our body uses fat as a fuel, but the efficiency of turning fat to energy is lower in late chronotypes.
The accumulation of fat puts late chronotypes at higher risk of cardiovascular disease and type 2 diabetes.
People who stay active during late hours burn less fat even during exercise, whereas early risers tend to use more fat for energy either at rest or physical activity.
Night owls vs. early birds
For this study, participants based on their chronotype were divided to two groups.
Their body composition (percentage of fat, muscle, and bone), body mass, and insulin sensitivity was examined for carbohydrate and fat metabolism.
Participants followed a standardised diet and fasted overnight while their activity patterns were tracked during the day for a week.
They also did two 15-minute sessions of moderate and high intensity exercise.
The results showed that those who were ‘night owls’ burned less fat for energy during exercise and rest than ‘early birds’.
They were also insulin resistant, meaning their body does not react well to blood glucose.
Therefore their bodies need more glucose and so they prefer carbohydrates over fats as a source of energy, which puts them at higher risk of developing diabetes and obesity.
Professor Steven Malin, the study’s first author, said:
“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.
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.
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.
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 study was published in the journal Experimental Physiology (Malin et al., 2022).
