Don't binge the Renée way

When Renée Zellweger put on two stone to become Bridget Jones she turned to the sort of diet most of us try to kick. Out went the Hollywood no-carbs diet, in came chocolate, pizza, peanut-butter sandwiches, burgers and doughnuts, washed down with a few gallons of Guinness.

A ban on exercise completed her transformation into a Bridget US size 12. Now her normal US size six, she is set to pile on the pounds again for the sequel.

While most women are constantly fretting about their weight, there are those who are seriously too thin, increasing their risk of osteoporosis and heart disease. In earlier life, being too thin can depress your immune system, causing fertility problems.

But Renée's gut-busting diet is the worst way to gain weight, say experts. "An average woman should eat 2,000 calories a day. To gain weight, you should eat an extra 500-700 calories," says Catherine Collins, spokeswoman for the British Dietetic Association-"To do this healthily you need to eat a balanced diet, only more of it. Eat three meals and three healthy snacks a day, such as fruit salad with a little cream, a scone with jam or a handful of cashew nuts or dried fruit.

"Avoid fatty foods, which are bad for cholesterol levels, but healthy fats, such as olive oil and oily fish, are an essential part of the diet.

"Protein will help you build muscle but too much can put a strain on the kidneys and can cause problems with dehydration.

Fruit and vegetables won't help you gain weight, but are vital for keeping blood vessels healthy. Carbohydrates should form the basis of your diet."

A healthy weight gain is between one and two pounds a week. As your weight stabilises, your metabolic rate should increase. But don't give up exercise - it will ensure you don't look flabby.

"You need to keep your cardiovascular system functioning effectively without burning too many calories," says Tim Bean, the personal trainer who runs Total Physique Management.

"Interval training - bouts of high and low intensity exercise - is best for this. It can take just a week to notice a difference."