Any diet that induces weight loss contains fewer calories than the user is burning. PERIOD. Different diets such as HCG, Paleo, Blood Type, etc. are nothing more than different marketing spins on a lower calorie diet. Diets like the Zone, South Beach or other relatively healthy diets when compared to more drastic fad diets, or the way typical Americans consume food, are simply different food plans that may (or not) allow you to stick to the amount of daily calories that produces weight loss. In other words some people feel better or more satiated consuming a higher protein diet allowing them to eat less and others feel more energetic on a higher carbohydrate food plan thus enabling them to stick to the proper calories to lose weight. The secret is to find a healthy plan (not one that omits or severely limits food groups) that allows you to stick to the amounts that produce the consistent results towards you body composition goal. This is why we have different options for you in the dotFIT program - all healthy but different so that they cover the spectrum of personal possibilities. And when all else fails, eat what you want until you reach your average daily intake that allows the goal.
Related questions:
What's the Zone diet? Why do some people say it's the only thing that works?
What's the deal with eating for your blood type?
Can you maintain the acid/alkaline diet long term?
Is injecting HCG for dieting safe?
Article - High Protein and Low Carb Diets:
http://www.dotfit.com/content-3071.html
Article - Body by Vi – 90-Day Weight Loss Challenge:
http://www.dotfit.com/content-35602.html
Video- Reviewing the Paleo Diet:
http://www.youtube.com/watch?v=5VYaFERn7og&feature=relmfu