GI stand for Glycemic Index and is a measure of the impact of food in your blood sugar. The diet focuses on the way in which different foods affect low sugar levels.
Basically, when blood sugar increases, insulin levels in the body are elevated, and as a result, the body doesn't burn fat. This is what the GI diet plan attempts to minimise.
On the GI diet there are no foods that you can't eat but the secret ie eating more low GI foods rather than high GI foods.
Some examples of low GI foods are Al Bran and Porridge, Soya and Linseed bread, cabbage and carrots and some examples of high GI foods opposite the above are Cornflakes, Bagels, and Parsnips.
Really the only way you can get your head around this diet is either to download some of the details on the website www.the-gi-diet.org or buy one of the diet books. One highly rated book is by Antony Worral Thompson simply titled 'GI Diet'.
I'd be really interested to hear anyone who has been on this diet as looking at it, once you understood the plan and fill your cupboards with low GI foods then you should by all rights find weight dropping off.