When You Exercise Can Be Key to Burning Fat

Sorry, night owls. The early birds do better in fat-burning, according to a study from Karolinska Institutet in Sweden and the University of Copenhagen in Denmark.

Exercising at different times of day can have different effects on the body due to the circadian rhythms of cells. So, to examine how timing influences fat burning, researchers at Karolinska Institutet and the University of Copenhagen studied what happened to mouse adipose tissue after a high-intensity exercise session that was done at two points during their daily cycle: an early active phase (similar to late morning for humans), and an early rest phase (similar to late evening for humans). They observed various markers for fat metabolism and analyzed which genes were activated in adipose tissue after the exercise.

The results showed that exercising during an early active phase increased the expression of genes related to breaking down fat, thermogenesis (heat production) and mitochondria in the adipose tissue - this suggested a higher metabolic rate. These effects only occurred when mice exercised in the early active phase and were not caused by food intake.

”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 Juleen R. Zierath from the Department of Molecular Medicine and Surgery and the Department of Physiology and Pharmacology, Karolinska Institutet.

Although mice and people share many basic physiological functions, there are important differences such as the fact that mice are nocturnal.

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