Do diets really work when trying to lose the pounds? i hear mixed reactions. some people say it works and others who stayed on the diet said no. why?

Nutrition & exercise: You've asked an excellent question & judging by number/percentage of overweigh & obese here in states, it's clearly a question that hasn't been addressed. It all depends upon what you eat & how much of it, too. There's some suggestion that timing might matter. Don't forget exercise, too. Try to focus on eating for your health rather than weight loss. Mediterranean diet has lots of research behind.

Yes: Caloric restriction actually has increased ability to predict weight loss than does exercise. Of course, the best is to combine the two. Increase your metabolic rate with exercise, strength train to gain more muscle. Most important is to make sure diet is healthy, has all nutritional components. Gimmicks don't work, but typically lower carb diets, with caloric restriction & exercise is best.