The diet is divided into three phases. Phase one involves going cold-turkey on sugar and the source of blood sugar surges (ie, bad carbs). Phase two allows the dieter to add back in some healthy carbohydrates and some fruit, and phase three is the maintenance phase, which goes on indefinitely. By phase three, you know which foods to eat and which to avoid. "It's the best diet for anybody to be on, whether you have to lose weight or not," says Agatston.
The maintenance phase is lifelong because the South Beach diet was developed as a healthy heart diet, not a diet to make you look good in a bikini (as the name might suggest). Agatston originally developed the diet to improve the blood chemistry of his patients. The fact that people lost weight (especially around the stomach) and kept it off, was a nice side-effect that led to a lucrative side-line in diet books.
Phase one bans fruit as many, especially tropical fruits, have a high glycaemic index. Diabetes UK says cutting out fruit is inadvisable as it contains vital vitamins and minerals which help to reduce the risk of heart disease and certain cancers. So isn't Agatston throwing the baby out with the bath-water? "The purpose of the first two weeks is to get rid of cravings," he says. "It's to stop the big swings in blood sugar and insulin levels. We encourage plenty of vegetables, and don't go into ketosis like Atkins. Fruit is very important; that's why we add it back in phase two." He says that the obesity epidemic in the US was caused by the myth that all carbohydrates are good for you. But as we now know, refined carbs stimulate further hunger by producing excess insulin. However, Dr Toni Steer, of the UK's Medical Research Council's (MRC) Human Nutrition Research, in Cambridge, says that Agatston has got it the wrong way round. "People become hyperinsulinemic [excess insulin in the blood] because they are overweight and they are overweight because they have eaten too many calories. Whether those calories come from fat, carbohydrate or protein is almost irrelevant." She also says that to claim overeating has only one cause - hunger - is an over-simplification. There are a myriad causes for overeating, some of them complex and psychological. But Agatston says that much of the perceived psychological stresses that cause people to overeat are simply dips in blood-sugar levels. Even those dips out, and your temperament evens out too. "Also, when you're under stress," says Agatston, "the adrenalin exacerbates the swing in blood sugar as well." It's one nasty merry-go-round.