I wouldn't be surprised if you put back all you lose plus some within a week or two, crash diets are useless as a long term solution you need to alter your lifestyle to some extent; if all else fails have part of your stomach sealed off.
All most fancy diets do is put money in somebody's pocket, and it ain't your own; I had 2 wives, both kept trying different diets, none worked for long.
Eat food without all the fancy sauces and garnishes, meat and veg cooked properly is all you need, no stodgy desserts, more fruit less pastry/sponge/suet pud; plus you need to have an active lifestyle, that doesn't mean spending pounds on a gym or a set of weights and exercise cycle. It means doing a bit more walking, swimming, cycling. Aerobics is just a fancy name for PT with music.Exercising in a Gym or on machines at home doesn't get any fresh air into your lungs, mind you with your fag intake you probably don't have enough lung left to take advantage of fresh air. I know the difference I used to smoke 30+ a day, if I hadn't given up when I did about 10/12 years ago I doubt if I'd still be here.
Sweets in moderation, a bar of choc lasts me at least a week. I may splurge from time to time with cream scones or dumplings but they are not part of a regular diet. I've never eaten a Pizza, don't intend to start either. I'm actually losing a bit of weight, about half a stone/3 kilos in a year
Stop and think, consider where you want to be in 10 or 15 years time, above or below ground.