Exercising in the morning burns more fat, study suggests

Exercise in the morning may burn more fat than at other times in the day, new research suggests.

Biological processes work differently depending on the time of day, due to each cell’s circadian rhythm – the natural cycle of changes in our bodies over each 24-hour period.

A new study by researchers at Sweden’s Karolinska Institute and the University of Copenhagen has found that mice have a higher fat metabolism when exercising at an early active phase in their daily cycle than an early rest phase.

This suggests that humans may also see more fat loss when working out late in the morning, as opposed to late in the evening, according to the scientists.

“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 Professor Juleen Zierath, of the Karolinska Institute.

The scientists set mice on a high-intensity workout at two points in the day, and studied the impact upon their adipose tissue, otherwise known as body fat.

They looked at which genes were active in adipose tissue, and discovered those involved with boosting the metabolism were more abundant in the morning slot – regardless of how much food the mice ate.

The researchers found that the earlier bout of exercise increased the expression of genes involved in breaking down fat by producing heat and mitochondria – indicating a higher metabolic rate.

”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,” said Prof Zierath.

Mice are a long-established model for studying human physiology and metabolism.

However, the researchers say that their comparison, published in the Proceedings of the National Academy of Sciences journal, is limited by the fact mice are nocturnal.

Previous studies have suggested that an early-morning workout on an empty stomach can help to speed up weight loss and boost energy levels.

It is thought that exercising early in the morning, when insulin levels are lower after having fasted overnight, pushes the body to tap into its fat reserves for fuel rather than merely targeting recently ingested calories.

Additional reporting by SWNS