It's more about what I don't eat .
So eg, don't eat ANYTHING made from white flour. Actually, I don't eat any bread and have found this has made a big difference. Also, fats in moderation obviously and only use olive oil or rapeseed oil for dressings or cooking. Plus I eat some protein at every meal as apparently its good for keeping hunger pangs at bay.
My daily diet needs to be based on 24% protein 55% carbohydrate and 19% fat, with the carbohydrates being low glycemic ones (shown in a chart in the book eg fruit,veg,wholewheat spaghetti, jumbo flake porridge (breakfast everyday), basmati rice).
A plate of food based on the diet would have approx 50% veg or fruit, 25% poultry, meat or fish (or othe protein source eg tofu) and 25% carbs such as pasta, potatoes.
There's a long list of "green" (low glyc index)foods in the book which you should try to stick to and I base my eating around. Then there's a yellow list and a red list which contain "in moderation foods" as they have a higher GI.
The higher the G Index, the quicker your body digests the food and converts it to glucose, either for use as energy or stored as fat. The idea of this diet is that you eat things that keep you fuller for longer and don't convert to glucose so fast that you are looking for food an hour later.
Hope this makes sense - sounds complicated but its not, once you've got the main principles in your head.