8 week blood sugar diet

Hi, I am in desperate need of a new hip - can't get one until my bmi 35-40. So a way to go for me. Went on a slimfast shake diet for past 3 weeks and lost 15kgs. But hard to drink those damn things 3 times a day - plus they have a lot of sugar & carbs - then found the 8 week blood sugar diet and started it last Friday. So nice to eat again - especially bacon - the moment I took the 2 slices from under grill was almost orgasmic! Anyhoo, managing to keep carbs at 20g and total calories at 800 - though often less. Am struggling to be convinced that eating all this food will give me continued weight loss. As I lost all the 'water weight' on liquid diet - is it likely I will lose 14kgs in 8 weeks as suggested by diet book?