This is the worst study that I've ever seen. Put someone on a 600 calorie per day diet and their metabolism automatically switches to hardcore survival mode where it tunes itself to grab hold of every calorie that it can and store it as fat. When they go back to eating a normal diet, as in 2000-2500 Calories per day, they will balloon, because their metabolism is still stuck in survival mode. A person who normally weighs 140 at 5"6' and has for all their life will gain weight like crazy if they're coming off of a starvation diet onto a regular, even healthy, diet.

With all the bad studies and advice out there, it's no wonder that people don't know what to believe and will flock to whatever miracle fad diet there is out there at the moment.