Yo-yo dieting: why the weight comes back.

Eight kilos off before summer, back on by Christmas, plus two. That's yo-yo dieting, and some people have been through it three times.

'I've lost the weight three times and regained it every time' is something I hear a lot. Then comes the fear of a 'broken metabolism'. Your body adapts. It doesn't break. And willpower usually has little to do with it.

How to spot yo-yo dieting

• Each time you lose a bit less. The diet from five years ago may now work less well and leave you hungrier.
• It comes back faster than it went. Months to lose, sometimes weeks to regain.
• You live on a switch. You're on a diet or eating 'normally', with nothing in between.

Why the weight comes back after a diet

When you eat far less for months, your body reacts as if food were scarce and defends itself.

It burns less. You weigh less, tend to move less without noticing, and waste less energy. This can last months, and 'eating like before' may be overeating.

It's hungrier. Your hunger hormone tends to rise and your fullness hormone to fall, and they can stay that way after the diet, at a stable weight.

Fat comes back first. If the weight returns quickly, it tends to be mostly fat, often round the middle. For example, you lose five kilos, three fat and two lean mass. You regain five, and four are fat.

The diet was built to end. Two or three months of rigid rules, then back to before. None covered eating out or work trips. And all-or-nothing diets are often linked to bingeing and guilt.

How do you stop yo-yo dieting?

By planning what comes next before you start. Lose slowly, protect your muscle and, at the weight you want, stay there a few months, eating more.

Go slowly. Aim for 0.4 to 0.8 per cent of your weight a week. The article on losing fat without losing muscle explains why. The harsher the cut, the harder your body usually fights back.

Protect your muscle. Two strength sessions a week and protein at every meal, during the loss and after. In one comparison, more than seven in ten people who had kept the weight off were still training. Among those who had regained it, fewer than three.

Put the free meal in the plan. Dinner out is planned, and the next day you're back to your usual meals, with no fasting to compensate.

Come off gradually, then hold the weight. Afterwards, raise your portions in stages, checking weight and waist once a week. Then a maintenance phase at least as long as the loss usually pays, with the same training and more food. Your body needs time to stop defending itself, and you to make it a habit.

If you've regained the weight three times, you know how to lose it. This time, write the plan from the end backwards: what you'll eat and how you'll train once the scales show your number.