When You Exercise Might Determine the Amount of Fat You Burn


Published: February 15, 2023 

Molly Campbell

Read time

 2 minutes

Researchers from the Karolinska Institute and the University of Copenhagen found that the timing of exercise may fine-tune fat metabolism in mice. The study is published in the Proceedings of the National Academy of Science (PNAS).

Exercise timing affects the body’s response

The time of day in which we exercise can impact the body’s molecular response to physical activity due to the varying circadian rhythm of cells. Scientists led by Professor Juleen Zierath, group leader at the Department of Physiology and Pharmacology at the Karolinska Institute, have explored how exercising at different times of the day can affect the body’s burning of adipose tissue (fat).

The study was conducted in mice, an established laboratory model for studying human physiology and metabolism due to shared characteristics among the two species.

Early active phase exercise increases expression of genes involved in fat breakdown

Zierath and colleagues subjected mice to a session of high-intensity exercise performed at two points in their daily cycle – the early active phase and the early rest phase (corresponding to the late morning and late evening for humans).