I could sit here and tell you why each of these diets is stupid. This is the approach most fitness experts take whenever someone asks them about the latest miracle weight loss cure they’ve heard about. But in my opinion, this is the wrong way to look at it, because for every diet you refute, some huckster can just make up some new line of bull to use on people to get their money.
The real problem isn’t simply a matter of dishonest people lying about a specific diet doing wonderful things for you. The problem is that the whole idea of going on a diet to lose weight fast is completely, horribly wrong for almost everyone. The entire concept is built to fail.
Rapid weight loss is inherently self-defeating. Fast weight loss requires that you run a massive calorie deficit; there is no other way to accomplish it. This is also known as “starvation.” The human body responds to starvation by slowing down your metabolism, conserving fat as much as it can and breaking down muscle through a process called catabolysis.
Will you lose weight that way? Sure you will. Some of it will even be fat. But the combination of metabolic slowdown and muscle loss means that as soon as you go off your diet, your body is poised to put on fat as rapidly as it possibly can. Hence the virtually inevitable rebound back to being overweight again.
And keep in mind that this is the best-case scenario; some fat diets are so stupid that they don’t even produce short-term weight loss, or are so unhealthy that attempting them will make you ill. But even when they succeed in the short term, long-term failure is built right into them.
Think about the real goal of losing weight, or more properly losing fat. The goal isn’t to get leaner for a short period of time and then get fat again; that would be incredibly stupid. The goal is to be leaner for the rest of your life. Yet these diets are at best only capable of giving you short-term weight loss, and the way they make you lose weight creates the conditions for getting fat again. Most of them don’t even pretend to have a long-term component, when the long term is the whole damn point!
And remember, this isn’t a matter of one fast weight-loss diet being bad. The whole concept of trying to lose weight fast by drastic calorie restriction is wrong-headed. “Dieting” in the sense most people think of it – a drastic diet change to lose weight fast – is simply self-defeating for almost everyone. If you want a long-term result, you need to change your lifestyle for the long term; nothing else can do the job. This applies to everything else in your life, so why wouldn't it apply to your health?