Recent research suggests we burn more calories at certain times of the day, but there are many factors to consider.

Are you trying to lose weight to improve your running performance? Or are you running lots of miles and trying to not to lose any more weight?

You’ll want to note a recent study published in Current Biology as what time of day you run could be factor in how many calories you burn. Scientists found energy expenditure was 10% higher in late afternoon and early evening compared to the early morning hours.

“The fact that doing the same thing at one time of day burned so many more calories than doing the same thing at a different time of day surprised us," says Kirsi-Marja Zitting of the Division of Sleep and Circadian Disorders at Brigham and Women's Hospital and Harvard Medical School, who was lead author of the study.

It could be an important scientific discovery for those who are using running as a means of losing weight. For these, exercising after work rather than first thing in the morning may represent the most economical way of doing so.

On the other hand, some who might be doing a lot of miles may struggle to stay above a safe body fat percentage. They might want to consider running in the morning to expend fewer calories than they would in the evening.

To calculate metabolic rate at different times on our own internal body clock, the seven subjects in the experiment were put into a special laboratory for three weeks away from the outside with no access to any indication of what time of day it was.

Co-author Jean Duffy added: "It is not only what we eat, but when we eat — and rest — that impacts how much energy we burn or store as fat. Regularity of habits such as eating and sleeping is very important to overall health."

Of course, several other factors come into play when deciding when to run. For example, you may burn more fat before breakfast although that’s a different thing to calorie expenditure.

Other studies have shown early evening to be the best time for strength or endurance as that is when the body temperature tends to be highest.

However, those who run in the morning are better at keeping to their training plans, research has also shown.

posted Sunday January 13th