This was inspired by another Ask YC post that mentioned the Hacker's Diet (http://www.fourmilab.ch/hackdiet/www/hackdiet.html).
After extensive research, I tried the Hacker's Diet and lost 60 pounds over 7 months. The big problem with HD is that it doesn't emphasize increasing your protein intake. As a result, I lost some muscle mass as well as fat. I kept the weight off for two years but eventually gained most of it back. Another criticism of HD is that you lose your energy--had I been working at the time I couldn't have pulled it off.
I recently started a medically supervised diet called a Modified Fast which does emphasize increasing protein and virtually eliminating carbs. One of my board members recommended the clinic and they claim they can do 15-20 pounds a month with no muscle loss or decrease in energy. I'm ahead of schedule but I'm only a couple days in so it doesn't really count. (The first 10 lbs are water weight.) I also take an appetite suppressant called phentermine during both diets.
Here's the Wikipedia link (http://en.wikipedia.org/wiki/Ketogenic_diet) for something similar to my current diet. They call it the Ketogenic Diet. (The whole point is to kick your body into a state of ketosis where it rapidly burns off all your fat. The protein is to make sure it doesn't also burn off muscle.)
So YC, have you ever tried to lose weight? If so, how?
"Diets" don't work because the word implies a temporary change in your eating habits. In order to maintain weight loss, you need to change your eating habits for the rest of your life.
Further, in order to be in good shape - not just maintain "low weight" - you need to eat well and exercise. For the rest of your life.