Whether you love to hit the gym in the morning or evening, the time of day at which you exercise determines how much fat you burn, according to a new study.

Researchers from Karolinska Institutet in Sweden and the University of Copenhagen in Denmark arrived at this conclusion after running an experiment on mice. They found that the metabolism of fats increased when the animals exercised in the early hours of the day.

Since biological processes rely on the 24-hour sleep-wake cycle, otherwise known as the circadian rhythm, physical activity at different times of the day affects the body in varied ways.

Regular exercise helps to shed body fat, showing that the more you work out, the more fat is broken down. This new research now shows that you can burn even more calories when you choose to work out in the morning.

The lead author of the study, Professor Juleen R. Zierath, and her colleagues worked to discover if the time of day one exercise could influence the amount of fat burned.

To carry out their experiment, the research team in Sweden subjected the mice to a bout of vigorous exercise performed in two different timing groups. The first group was the early active phase, which represented late morning in humans, and the second group was the early rest phase mimicking late evening sessions in humans.

They then studied the adipose tissues of the mice at various time intervals for up to 20 hours to determine the effects of time and exercise on the metabolism of body fat.

The team also wanted to figure out what genes were activated in the adipose tissues (also known as body fat), during the exercises. 

What the Study Revealed

By the end of the study, the authors found that genes involved in the breakdown of body fat were increased following physical activity performed in the morning. They also observed that more heat and mitochondria were produced—indicating increased metabolism of fats.

These effects were prominent in mice that exercised in the early active phase, regardless of how much food they ate.

“Our results suggest that late morning exercise could be more effective than late evening exercise in terms of boosting the metabolism and the burning of fat, and if this is the case, they could prove of value to people who are overweight,” says Professor Zierath.

Since mice’s physiology and metabolism are similar to those of humans, the researchers say that the relevance of these findings will likewise extend to humans. 

Above all, it is evident that there is a right time to exercise. People aiming to burn extra calories and double up the health benefits of exercising can achieve this by exercising in the morning. 

A prior study that looked at over 85,000 participants also showed that those who are physically active in the morning have the least chance of developing a stroke or heart disease.

Findings from this study go further to add to the truckload of benefits that come with working out in the early hours of the day. However, the researchers still see the need to further validate their findings on humans before drawing any reliable conclusions.

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