Does the Time of Day You Exercise Matter?

University of Copenhagen researchers say they have learned that exercise may have a different effect on the body depending upon the time of day.  In a new study, the researchers recorded, in mice, that morning exercise seems to more effectively increase metabolic response in skeletal muscle while evening exercise seems to more effectively increase overall energy expenditure for a longer period of time.

Novo Nordisk Foundation Center for Basic Metabolic Research Associate Professor Jonas Thue Treebak explains, “There appear to be rather significant differences between the effect of exercise performed in the morning and evening, and these differences are probably controlled by the body’s circadian clock.”

The study, which is in collaboration with researchers out of the University of California, Irvine, analyzed several effects in the muscle cells. This includes things like transcriptional response and effects on the body’s metabolites.  These results, the authors say, indicate the effects of exercise seem to be stronger in the morning but, overall, are controlled by a central mechanism that involves the protein HIF1-alfa, something that directly regulates circadian rhythm. 

The study author goes on to say, “Morning exercise initiates gene programs in the muscle cells, making them more effective and better capable of metabolizing sugar and fat. Evening exercise, on the other hand, increases whole body energy expenditure for an extended period of time.”

Essentially, the authors theorize that morning exercise may better serve people who are severely overweight or are trying to mitigate type 2 diabetes. That is because, again, morning exercise appears to more effectively metabolize sugars and fats. Evening exercise, then, better serves those who may want more endurance in the later hours. 

All that said, the researchers remind this discovery is still quite fresh and they do not know how to interpret the results.  More specifically, they cannot necessarily recommend which type of exercise is best; at least, not at this point. Certainly more research is needed to determine if time of day influences other factors when exercising.  

Treebak concludes, then, the team is quite eager to extend the research to human studies.  This, he hopes, will reveal if timed exercises could be determined as a possible treated for those struggling with metabolic diseases. 

The results of this study are slated for publication in the next issue of the medical journal Cell Metabolism. 

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