My IB Biology teacher does that diet. It's one of those all protein diets that's supposed to help you lose weight by preventing you from taking in fats and carbs. It works because protein is very hunger satisfying and filling, so you won't get hungry easily. Hot dogs are a bad idea unless they're 100% lean beef hot dogs. Stuff like eggs and turkey are pretty popular.
I don't usually go on diets because they don't work as well as the traditional exercise and eating healthy food. If you do stuff like cutting your food intake in half for a month or two, you can lose weight fast though you'll gain weight three times faster when you return to your normal diet. [You body gets used to the low calorie diet so when you intake more calories, the body tends to take up more than usual.] If you do plenty of exercise, sleep well, and eat healthy foods, you'd lose weight fast.
But going on a pescitarian, vegan, or vegetarian diet for a short period of time also works great. But it doesn't always work great for everyone. When my friend became vegan, she gained about 10 lbs all of a sudden. [though, she really did need that because she was 85 pounds at 5'4"] But I, on the other hand, lost weight since I became pescitarian.
There is no fake fat per se unless you want to consider chiral fat molecules or something as fake...
Margarine has been proven to be good for you because many times it includes some essential fatty acids such as vitamins A and D3, though they can be unhealthy because they do contain some trans fats. Butter, in large quantities, is very bad but in small quantities it's harmless. But overall you want to go for the monounsaturated fats like the ones in fish [omega-3] and the essential fatty acids. Some of my friends have really bad type 2 diabetes, but they were able to control it just fine by having a diet that's high on protein and low on sugars and "bad" fats.