You need to avoid carbohydrates, so that's a no-no to bread, cakes, rice. pasta, cereal, sweet drinks, flour-based sauces and any processed food with a high sugar content.
On the other hand, you can have lots of meat, fish, eggs, cheese and plain yoghurt. You can also eat most fruit and veg, but not bananas (and there are one or two other fruits that have a high sugar content, but I can't remember them all). All this means I can usually have a yoghurt or perhaps egg and bacon for breakfast, a mixed salad with some cheese for lunch, and chilli con carne for dinner with strawberries and cream for dessert.
You can drink milk. tea, coffee and cocoa as long as they're not sweetened, and spirits are preferable to beer. Also, try to drink white wine rather than red.
You have to be really strict with yourself for the first couple of weeks, as the idea is to kick-start your body into weight loss, or ketosis as they call it. After this you can gradually start to introduce small amounts of nuts and various other foods. You will reach a stage where weight loss stops, and this is the point where you get strict again and repeat the process ad infinitum until you reach your optimum weight, at which point you move onto a maintenance plan which becomes pretty much your diet for life.
I've put this very simply, as it's quite a lengthy, scientific explanation of how you make it work for you. Therefore you'd be wise to buy the book:
http://www.amazon.co....qid=1268502632&sr=8-1 .
contd.