Exercising in the morning may be best way to burn fat, study finds

Physical activity at different times of the day can affect the body in different ways, researchers say

A woman and her dog run along the bank of the River Cam in Cambridge at sunrise. PA

Undertaking exercise in the morning may be the most effective way to burn fat, research suggests.

An increase in fat metabolism has been linked to doing physical activity at the right time of day, according to the study, carried out on mice.

Researchers found that mice who exercised in an early active phase — which corresponds to morning exercise in humans — increased their metabolism more than mice that exercised at a time when they usually rest.

“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, " said Juleen Zierath, of the Karolinska Institutet's department of molecular medicine and surgery and department of physiology and pharmacology.

Researchers say physical activity at different times of the day can affect the body in different ways, as biological processes depend on the circadian rhythms of the cells — the 24-hour cycle that is part of the body’s internal clock.

To determine how the time of day affects the burning of fat, researchers at the Karolinska Institutet and the University of Copenhagen studied the body fat of mice after a session of high-intensity exercise on a treadmill performed at two points of the daily cycle.

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They looked at an early active phase and early rest phase — corresponding to a late morning and late evening session, respectively, in humans.

The scientists studied various markers for fat metabolism and analysed which genes were active in fat tissue after exercise.

They found that physical activity at an early active phase increased the expression of genes involved in the breakdown of fat (adipose) tissue, thermogenesis (heat production) and cells in the adipose tissue that indicate a higher metabolic rate.

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According to the study, these effects were seen only in mice that exercised in the early active phase and were independent of food intake.

“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,” added Dr Zierath.

The findings are published in the PNAS journal.