I have done loads of dieting over the years. For me, the answer was simple - either cut down on your carbs (energy source), or make sure your exercise output is greater than your energy input.
I lost loads of weight previously really quickly doing the Atkins diet (cutting out carbs almost altogether), but this is not healthy. Now, I am just cutting down on carbs, so its more of a lifestyle change than a diet. The weight is coming off really slowly, but, because I just adjusted my way of eating, I believe it will stay off, whereas with an extreme diet, you lose the weight quickly, but then put it back on again when you return to more normal eating.
check this out for a diet.
Breakfast. 3 wheetbix, coffee.
lunch. maggie 99% fat free 2 minute noodles
orange for a snack.
dinner. lean meat 3 veg.
awesome.