The diet ranks carbohydrates according to their effect on the body's blood glucose levels. Carbohydrates that have a low glycemic index produce only small fluctuations in blood sugar and insulin levels, whereas high-glycemic foods cause a sudden sugar rush.
High-glycemic foods include all processed foods, such as white bread and rice, as well as fried foods, and especially potatoes. Low-glycemic foods include pulses and most vegetables, and as a result, they cause a longer and slower release of sugars into the blood.
Although the diet was originally designed to help people overcome diabetes, its pioneers also discovered that people were losing weight. It's a result that has been vindicated in many a study since, and now even the Cochrane Review has put its seal of approval on the diet.
It reviewed six randomised and controlled trials that compared the diet with diets that included foods with a higher glycemic count. The researchers confirmed that the low-GI diet outperformed other diets, and was especially good for people who were obese as it allowed them to eat many normal foods without having to stick to a rigid, and restrictive, diet plan.
The Cochrane researchers say that the diet doesn't just help you lose weight, it's good for you, too. People who stayed on the diet also saw their body mass index, total cholesterol and LDL cholesterols all dramatically reduce.
(Source: Cochrane Database of Systematic Reviews, 2007; 3: no. CD005105).