CHEAT: Eat back calories

DEETS: It goes against everything logic – and weight loss lore – tells us. Against advice to create a caloric deficit to lose weight, fat loss is different (for the really intricate science, see p. 58).

When it comes to liquidating lipids, there's a delicate tipping point, where measures aimed at fat loss can actually undermine the goal. Creating too big a caloric deficit (say, eating 2,000 kilojoules below your total daily energy expenditure and knocking off another 2,000 in the gym) will, over time, predispose you to fat gain.

"If you lose weight too fast, you're likely to lose a quarter to a third of your weight loss as muscle, and that directly compromises your metabolic rate," O'Neill says. "If, for example, you drop 15 kilograms really fast, you could lose five kilograms of muscle – that's the equivalent of five kilos of body fat you're not burning up anymore.

"You should never lose more than a kg a week, with a much better target being a maximum of 0.5 kg a week, which will ensure that more of your lost weight is fat rather than muscle," O'Neill says. Effecting a caloric deficit of about 2,000 kJ a day – or quarter of your daily intake – will enable your body to use stored fat, says dietitian Dr Alan Barclay.