Fasted training: easy work holds up.

Fasted training works for easy steady effort, such as a brisk walk or gentle cycling. On an empty stomach your insulin is low, so you use more fat. For weights and hard work, it is better to eat something small first. By the end of the month, your weight follows the whole day.

The alarm goes at 6:30 am, you train at 7, your first call is at 8, and you have eaten nothing. I see this often in the business owners I work with. They train fasted to burn more, then drag themselves through the morning.

Is fasted training good for you?

It depends on your muscle mass and on what you put into the session. On an empty stomach there is little sugar available, so your body takes more fat. But it pays off if you are already in training.

• Fat travels both ways. Fatty acids leave your fat cells when you are fasted and while you move, and they go back in after meals. What pushes them out is your insulin falling.
• The night prepares the ground. After the twelve hours between dinner and breakfast, the ones in the article on intermittent fasting, an hour of brisk walking releases more fat than a meal two hours before.
• If you are not yet in training, eat something first. Training fasted can cost you muscle rather than fat.

Does fasted training burn more fat?

No. When fasted cardio was compared with cardio after a meal, with the same calories the fat loss was the same. Fasting changes the fuel of that session, not the month's result.

Why the sums do not add up. When you stay fasted, your resting metabolism slows a little, and a slow engine burns less fat: you release more fat but burn less of it. Carbohydrates are also what turn your thyroid hormone into its active form, so always training fasted when you are untrained slows the hormone that sets how much you burn.

Which workout holds up on an empty stomach?

Easy steady work: brisk walking, gentle cycling, an easy swim, never hard enough to lose your breath. This is the easy cardio from the article on zone 2, which also has the durations.

Weights and intervals do not. Fuel is not the problem. A weights session empties only about forty per cent of your glycogen, the sugar stored in your muscles. What you lack is drive, and your morning cortisol is already high, so you are more likely to lose muscle.

The small meal that solves it. Before weights, have something small and mainly protein, with about 15 grams of carbohydrate: an egg and half a banana, or Greek yoghurt with a piece of fruit. You burn those 15 grams in the session, they do not slow your thyroid and they keep your cortisol in check. Leave at least an hour.

Your first meal after counts. On other days, one meal matters as much as any other. When you train fasted you really need it: protein, fruit and a proper carbohydrate, within three hours. A savoury breakfast works well. And you start better after a full dinner the night before.

Tonight, decide which session tomorrow is. If it is easy, go out fasted. If weights are on the plan, leave something small by the coffee machine.