i want to address your post on different levels.
first, if your goal is for her to lose the weight, i think you went at it the wrong way. try positive reinforcement instead. like when she's eating write or working out, notice it and give her props. or if you notice she lost a little, give her props and the
face. if your girl notices that you find her sexier, she will actively try to lose the weight and do the research herself because being sexier to you increases the power in the relationship. negative reinforcement will make her feel like she is incapable of doing it and in turn lowers her motivation. shyt might even make her eat more.
As far as getting with a chubby chick hoping she would lose weight, you played yourself. she's probably fat because she's lazy and a glutton. these are traits that are typically ingrained from an early age. that's like getting with a smoker and telling her "ok, i'll be with you but i want you to make efforts to stop smoking"
as far as the convo itself, it's funny how the women are saying OP is a jerk but yet overlook the fact that dude kept telling her he's ok and to just leave it alone but she kept nagging him to spit it out. was dude suppose to lie? would y'all want your men to lie to you when you keep nagging him to be honest? if you don't want the answer then don't ask the question. and before y'all say he could have been more tactful, this is one of those situations that the emotion and tone would have been a lie if he was more tactful. i think some of y'all like to get lied to.
one more thing to the OP, next time please paragraph your shyt breh.