Well, if you still like to eat and you're in good physical condition, I saw this on either Nightline or ABC News last month or so. It's on the extreme side, developed by a NASA scientist, Ray Cronise. It's called the "cold diet" or "ice bath diet". They showed a guy doing 15 min ice baths and said he did this 3 or more times per week. Also took 15 min walks in freezing weather wearing just a t shirt, shorts, a knit cap, gloves, shoes and socks. Apparently, he studied Michael Phelps and his 20,000 calorie daily intake when training and the conclusion was the body spent more energy fighting the cold water more than just the exercise. Again, don't try this if you have any phyical issues or heart condition! Here's the link to the article, there's no video even though one shows up, it's for something else.
Weight Loss: NASA Scientist Ray Cronise Chills His Body to Burn Calories - ABC News