Fat Woman is feeling stabby. Fat Woman doesn't say much about how much weight she's lost but when a friend mentions it to new people Fat Woman allows herself to accept the praise for losing a hundred pounds in a gracious and appropriately modest fashion. What Fat Woman doesn't expect is for someone to immediately trump her achievement with their own, but she can let it go as it probably comes under wanting to share experiences. What make Fat Woman want to start poking sharp metal objects at people is when her weight loss achievement is trumped by someone who has lost weight through surgery. If you announced you'd made £100 by working hard for two days and someone else announced they made £10,000 by putting all their money on a horse you'd feel rather like they were suggesting that their way was better and that they had achieved more. There would also be an implication that they were a bit smarter than you. This particularly rankles with Fat Woman because she could have had her pick of weight loss surgery on the NHS. Instead she chose to invest huge amounts of time and money into getting healthy. It's like someone saying to you "My self-mutilation is better than your self-control." Fat Woman is not going to validate anyone else's weight loss choices, especially not by decrying her own.
Fat Woman felt slightly less defensive about this issue when she found out that someone who had been upsetting Fat Woman quite a lot hadn't actually lost any weight since her surgery. Fat Woman feels very sorry for surgery woman, but felt very glad that wasn't her after all.