So what IS the best way to do it? Nordic skiing, cycling and rowing

THE amount of energy you expend in terms of calories burned depends on the length and intensity of your workout. A heavier person can burn more calories while exercising than a lighter one because they have a greater burden in terms of their body weight.

Dr King says: ‘The rule of thumb for a runner is that you burn a calorie for every kilogram of body weight per kilometre you travel. So if you weigh 70 kilos and run for six kilometres, you’ll burn 420 calories.

‘Sports that require you to move large muscle groups over a long period – such as Nordic skiing, rowing, running and cycling – are the highest calorie-burners.’

The digital calorie-counter on a treadmill uses one of a variety of methods to determine how many calories you are burning.

The simplest use your body weight and pace. More advanced models will take readings of the incline for your workout and your heart rate. In theory, calorie-counters that take in more variables can be more accurate.

It’s easiest just to use a fitness tracker. The one I use, the Fitbit Charge HR, is a wide rubber band with a traditional watch buckle which measures heart rate from the pulse at the wrist.

It also contains an accelerometer which measures steps taken and distance covered, and an altimeter to monitor if you’re travelling up or down. To make it ultra-accurate, you give it the data needed to calculate your basal metabolic rate (BMR).

This is the rate at which you burn calories at rest just to maintain vital body functions like breathing, heartbeat, and brain activity.

Your BMR usually accounts for at least half of the calories you burn in a day and is estimated based on the physical data you entered when you set up your account: gender, age, height and weight.

When you use one, you’ll notice you start the day with calories already burned, without having done anything. This is by far the most accurate method of measuring calorie-burn.