Hailing from Florida, the South Beach diet is currently hugely popular in the States, with over five million copies of the book sold so far. Our diet plan review explains the theory behind this latest weight loss favourite.

The South Beach diet promises to help you lose 13lb in two weeks, with most of the weight loss from your midriff. It was created by American cardiologist Dr Agatston for his heart patients, but he discovered it also had the side effect of enabling them to lose weight. Diet meal plans and recipes for the South Beach diet aren't low-carbohydrate or low-fat, but instead encourage dieters to eat only the 'right' carbohydrates and fats. The programme is based on the glycaemic index: foods which take longer for your body to break down into sugar are better than foods which break down quickly, causing fluctuations in blood sugar level.

For the first two weeks, the programme severely reduces carbohydrate intake, then gradually reintroduces low-GI carbohydrates. Saturated fats are replaced by unsaturated fats in the diet meal plans. Low GI foods release sugar slowly into the blood, leaving you feeling full for longer periods. What's more, your body has to produce less insulin to break down low GI foods, which stops you from becoming resistant to its effects. This means that your body can burn fat more efficiently.

The programme has three phases:

Phase One - 14 days

Carbohydrates are banned, to help your body's insulin and blood sugar levels to stabilise.

Phase Two

Low GI carbohydrates only are allowed until you've reached your target weight.

Phase Three

A wider variety of food is introduced. This phase is designed to keep your weight constant, and you are recommended to follow this diet for the rest of your life.