Science Shows The Importance Of Timing Your Workouts

Since biological processes rely on the circadian rhythms of the cells, physical exercise at various times of the day may have varied effects on the body.

According to a new study from the Karolinska Institutet in Sweden and the University of Copenhagen in Denmark, mice that exercised during an early active phase, which is comparable to a morning workout for people, had higher metabolisms than mice that exercised during a time when they would typically rest.

The findings were published in the PNAS today.

Research teams at Karolinska Institutet and the University of Copenhagen examined the adipose tissue of mice after a session of high-intensity exercise performed at two points in the daily cycle, an early active phase and an early rest phase, to determine the effect of exercise timing on fat burning (corresponding to a late morning and late evening session, respectively, in humans).

Researchers looked at many fat metabolism indicators and analyzed which genes were turned on in adipose tissue during physical exercise.

The researchers discovered that engaging in physical exercise during an early active phase enhanced the expression of genes involved in the breakdown of adipose tissue, thermogenesis (the generation of heat), and mitochondria in the adipose tissue. This indicated a greater metabolic rate. These effects were only seen in mice that worked out in the early active phase and were not affected by how much they ate.

According to Professor Juleen R. Zierath, the findings of the new study, ”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.”

Mice and people have many of the same basic bodily functions, and mice have been used as a model for human physiology and metabolism for a long time. But there are also big differences, like the fact that mice only come out at night.

”The right timing seems to be important to the body’s energy balance and to improving the health benefits of exercise,” adds the professor, “but more studies are needed to draw any reliable conclusions about the relevance of our findings to humans.”

Source: 10.1073/pnas.2218510120

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