I've come to the conclusion that diets intersect with soveriegnity of one's body and identity. People can become quite threatened, and therefore irrational. The tell is how they are unable to simply say, "You look great! Congrats on losing weight!" Especially when said person is chubby, fat, diabetic, etc. You know they would like to be thinner, too. If you win a race, people high-five you but if you lose weight, they often resent the hell out of you. It's a good way to separate the wheat from the chaff, character-wise, however.