CHEAT: Eat before a workout
DEETS: While intuitively it feels as though without a piece of toast to burn, your body will make a beeline for your fat stores, fasted morning workouts aren't as magical as they seem.

"You'll burn a slightly bigger percentage of fat, but do you feel energetic enough to work out sufficiently before breakfast?" asks O'Neill.

In other words, you may burn a bigger slice of the pie from fat but lose the edge when you can only reach 50 per cent intensity rather than 70. The other unfortunate flow-on is that survival mechanisms may cause you to overcompensate with subsequent meals by dialling up your hunger beyond what your body needs to function. You can wipe out a caloric deficit (the one you gave up the doona to achieve) with a single muffin.

"You've got a whole day to cancel out the benefits of what is really a marginal difference in fat burning," O'Neill warns. Dr Enriori says excessive caloric deficits provoke a physiological crisis response that works against fat loss. "As soon as you start losing weight you start to lose energy expenditure."