Many people decide to diet to lose weight because they hate and fear exercise. This is rather self-defeating, as what often happens is that the dieter becomes sluggish from the lowered energy intake, and from that they become depressed or anxious. In order to deal with their anxiety, they turn to snacking, larger portions or sugary food to "reward" themselves for their extended abstinence. Then, they get fat, hate themselves, pick a new diet, and then start the cycle again.

A person who eats nothing but pizza, marshmallows, multi-vitamins and cotton candy but works out strenuously will likely be far healthier - and perhaps even thinner - than your average dieter who eats low fat cookies and salad but never works out. They'll also be happier, because they can eat whatever they feel like and get to enjoy the euphoric high that comes from strenuous exercise. It'll be easier for you if you eat healthily and also work out, but if you think that you're likely to have much success without exercise, you're simply stuck in wishful thinking.

The body reacts to a low calorie diet by slowing metabolism down and releasing hormones that make you feel drowsy. This undermines efforts at exercise and generally results in weight gain over an extended period of time. That doesn't mean you can't lose weight by starving yourself - technically, it does work - but you will gain weight faster when you return to healthier caloric intake because the body's metabolism will be geared for starvation.