Q Is it true that a person will use the same amount of calories over a given distance regardless of how fast or slow they run? My theory is that two runners with an identical metabolic rate would use the same number of calories over a set course.

A The rate at which our bodies burn calories is determined by many factors, of which time and distance are only two.

First the science bit: our basal metabolic requirement (BMR), the number of calories we require over 24 hours, is dependent on age, sex, height and weight. A 64kg man, for instance, has a BMR of about 1550 calories, while a 64kg woman’s BMR is around 1400 calories.

As you lose weight, your BMR drops. This effectively means that you have to exercise harder and longer to burn the same number of calories. Lots of studies have confirmed this. Most recently, for example, researchers at Dunn Nutrition Laboratories in Cambridge found that overweight people burned more calories in a step test than the leaner participants.

So what about your theory? Well, you’re right. Even if one of your identical runners ran five miles in 30 minutes, and the other jogged the same distance in 45 minutes, there would be a negligible difference in the calories burned. In fact, this would hold true even if one walked the distance.

The difference comes once the two runners have stopped. Several studies show that there is more likely to be a prolonged rise in metabolic rate (around five per cent higher than normal) for up to eight hours after intense exercise than after moderate physical activity. This means that the faster runner in your scenario stands more chance than the slow jogger of burning some extra calories after he has finished.

—Peta Bee, RW Nutrition Editor