Have you tried the Zone Diet?

The rationale behind this diet is that your body needs to have energy in order to live. You can't simply stop eating or stop eating entire groups of foods and expect to be healthy or to feel good as you do. Within each food group are vitamins and minerals your body needs to stay fit.

When you deprive yourself, you will reduce the calories you are eating - and this does lead to weight loss - but you can also lose muscle mass which can then slow your metabolism.

The Zone Diet and Weight Loss