I got a friend like that. Started dating a fatty and all he talks about is how she is ten years younger than him and that he is "winning" by dating a twenty two year old(at the time they started dating.) For the past couple years she has been on some fad diet or another. Plus side of all her stupid diets is that I never get stuck double dating because they're usually so stupidly restrictive that I can easily say "oh. My girl wants to go to XYZ they don't serve that type of food."