Dieting is something that shouldn't be taken lightly and before even starting a diet, you should check with your doctor and have a complete physical before even attempting to diet.
A lot of diet programs that are out there, are not the same nor do they all agree as to what or how you should diet. Some tell you to go nonfat, less carbs, lower the calories, and many other things. The best way to lose weight and is almost guaranteed to lose the weight. It is to eat smaller portions, drink plenty of fluids and exercise regularly.