Does the Time of Day for Working Out Matter?

From helping to reduce anxiety, boosting sleep to helping with weight management, the pros of physical activity outweigh the chore of doing it.

Knowing the best time to exercise for maximum benefits can be essential for those looking to start a new workout routine. To aid in this, a new study published in Cell Metabolism has mapped out the chemicals for evening and morning exercise, showing how they affect overall health. 

Background: Maximizing the Benefits of Exercise

Knowing the right amount of exercise can be essential when targeting specific fitness goals. For example, the CDC recommends 150 minutes of exercise a week (5 days a week for 30 minutes) to maintain current weight. This regular exercise regimen can also help strengthen bones and muscles and deter cancer and obesity.

To fully maximize the benefits of exercise, it’s essential to understand your circadian rhythm, or the body’s natural sleep-wake cycle, repeating approximately every 24 hours. Circadian rhythms can get tweaked by poor sleep, jet lag, or other factors. Thankfully, exercise may be able to help reset a circadian rhythm.

Because exercise is closely linked to our body’s natural rhythms, the time of day one works out can play an essential role in maximizing the health benefits of exercise. 

According to professor Juleen R. Zierath from the Novo Nordisk Foundation Center for Basic Metabolic Research (CMBR) at the University of Copenhagen: “A better understanding of how exercise affects the body at different times of day might help us to maximize the benefits of exercise for people at risk of diseases, such as obesity and type 2 diabetes.” 

Analysis: Mapping Metabolism

To understand how the different exercise molecules work throughout the day, researchers at the Computational Discovery Research from the Helmholtz Diabetes Center at Helmholtz Munich (as well as a team of other universities) looked at mice. Researchers performed a variety of experiments with mice exercising either in the morning or evening. After a period of time, the mice’s blood and tissue samples were analyzed. From this analysis, researchers were able to map how chemicals moved and worked throughout the body at different times of the day.

This chemical map gave researchers deep insight into how certain tissues communicate with each other using chemicals. The chemicals stimulated by exercise can help to ‘realign’ tweaked circadian rhythms in specific tissues. “Not only do we show how different tissues respond to exercise at different times of the day, but we also propose how these responses are connected to induce an orchestrated adaptation that controls systemic energy homeostasis,” explained Associate Professor Jonas Thue Treebak from CBMR at the University of Copenhagen, and the co-first author on the paper.

Outlook: Timing is Everything with Exercise and Circadian Rhythm

As tweaked circadian rhythms have been correlated to increased risks of obesity and type 2 diabetes, fixing a tweaked circadian rhythm is important for improving overall health. While this study was done on mice, finding similar results in humans could offer important information about health, but could reshape the exercise industry.

According to the co-first author and Assistant Professor in the Department of Biology and Center for Biological Clocks Research at Texas A&M University, Shogo Sato: “Despite limitations, it’s an important study that helps to direct further research that can help us better understand how exercise, if timed correctly, can improve health.”

Kenna Castleberry is a staff writer at the Debrief and the Science Communicator at JILA (a partnership between the University of Colorado Boulder and NIST). She focuses on deep tech, the metaverse, and quantum technology. You can find more of her work at her website: