Scientists reveal best time to exercise for burning body fat

Regardless of the time of day, any physical activity is beneficial. However, for some individuals, the best workout routine is one that encourages them to move frequently and consistently.

According to media reports, a recent study in mice suggests that exercising in the morning may provide added benefits for those looking to enhance their workout.

In fact, the new research states that exercising in the morning may be the most efficient method of burning fat. The study conducted on mice indicates that engaging in physical activity during the appropriate time of day can boost fat metabolism.

Study findings

The findings reveal that mice who exercised during their early active phase, equivalent to morning exercise in humans, experienced a greater increase in metabolism compared to mice that exercised during their usual rest phase.

Since mice are nocturnal creatures, their daily cycle differs from that of humans. However, these phases align with the morning and evening cycles for people.

Speaking about the results of the study, professor Juleen Zierath, who is with the department of molecular medicine and surgery as well as the department of physiology and pharmacology at Karolinska Institutet in Sweden, is reported to have said, “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.”

Scientists suggest that the impact of physical activity on the body varies depending on the time of day since the biological processes of cells are governed by the circadian rhythms - the 24-hour cycle of the body's internal clock, The Independent explains.

To investigate the effects of exercise timing on fat burning, researchers from Karolinska Institutet and the University of Copenhagen examined the body fat of mice after conducting high-intensity treadmill exercise during two different points of the daily cycle.

The researchers reportedly examined the mice during an early active phase and an early rest phase, which would correspond to a late morning and late evening exercise session, respectively, in humans.

The scientists also evaluated several indicators for fat metabolism and examined the genes that were activated in the fat tissue post-exercise.

Their findings showed that exercising during the early active phase resulted in higher expression of genes responsible for the breakdown of adipose (fat) tissue, thermogenesis, and metabolic rate-enhancing cells within the adipose tissue.

The study also reportedly revealed that these effects were exclusively observed in mice that exercised during the early active phase and were not influenced by food consumption.

Best time to exercise

Shogo Sato, PhD, an assistant professor from the Department of Biology and the Centre for Biological Clocks Research at Texas A&M University in College Station, told Healthline that this study “revealed that the impact of exercise on metabolism in adipose tissue relies on when to exercise.”

In particular, the results indicate “that the early active phase is the appropriate time of exercise for metabolic adaptation in adipose tissue,” Dr Sato said.

According to a previous report in The New York Times, chronobiology, which is the scientific field that explores the impact of timing on our bodily responses, has gained significant attention.

Numerous recent studies have also examined how the timing of meals, such as exercising before or after breakfast, affects weight management.

However, little has been known about whether the timing of exercise itself affects weight loss with workouts.

Prof Zierath adds, “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.”

An earlier study

This study builds upon an earlier mouse study conducted by Sato and some of the same researchers, which was published last year in the journal Cell Metabolism.

Sato additionally points to another previous study he reportedly conducted with the same researchers, which was published in the journal Cell Metabolism in 2019.

This research concentrated on the skeletal muscle, which, according to Sato, is "responsive to exercise stimulation."

The study showed that exercising during the early active phase had a considerable influence on specific metabolic pathways, such as glycolysis, lipid oxidation, and the breakdown of branched-chain amino acids.

Overall, the new research and earlier studies provide a more comprehensive insight into how exercise timing affects metabolism at a particular tissue level, Sato said.

This latest information has the potential to aid in the development of time-of-day-based exercise programmes, which can enhance metabolic function in individuals with type 2 diabetes or other metabolic illnesses.

Similarly, other research conducted by Zierath and her colleagues has investigated whether exercise at specific times of day can be beneficial to individuals with type 2 diabetes.

However, as Sato points out, "an appropriate time of exercise in humans, depending on different disease risks, such as cardiovascular diseases and aging, is (not yet clear).”

Thus, more research is required to understand the molecular mechanisms behind the impact of exercise timing on metabolism before doctors can suggest specific exercise timings to patients, Healthline explains.

The results of this study are published in the PNAS journal.