To the OP, so how did the friend change the rules of the game to make it not worth it? Did he inject carbs somehow?
And yes, if a fat-burner takes in more fat calories than fat calories are burned, he'll gain weight. Duh. The point is that a rea fat-burner won't WANT to take in all those fat calories. He'll be full, he'll forget to eat, he'll get sick, etc.
5'0" female, 45 years old. Started Primal October 31, 2011, at a skinny fat 111.5 lbs. Low weight: 99.5 lb on a fast. Gained back to 115(!) on SAD chocolate, potato chips, and stress. Currently 111.