Will this diet mess up my metabollism?

My friends and I have started a new fitness regime to get a good bikini body for the summer and will cutting out sweets and fizzy drinks mess up our metabollism? We will be burning 300 calories a day or more and not eating sweets, chocolates or drinking fizzy drinks, when the diet is over and we eat a sweet, will we put on a whole lot of weight? If yes, is there any other way to lose weight fast. I dont want to starve myself and eating a bal;anced diet and working out hasnt exactly worked. Help!