There are thousands of variables involved in weight, there is no "fairness" in it. Some thin folks eat a lot, don't exercise and stay thin (though some will start to gain after certain life events, such as; puberty, pregnancy, middle age, retirement...)
Even if you tried to live exactly like X you might not get the same results, but there's a good chance that you weren't living as much like her as you may have thought. You did say that X exercised less than you did (but didn't say she never exercised), but you did imply that you gave up exercise altogether. Maybe you didn't mean it that way, but that's what came across.
In my 30's, after yoyo dieting since kindergarten, I gave up dieting. I became a fat accepting, joy embracing fat person at a high but stable weight. I gained about 10 lbs above my highest weight and stayed there at a stable weight for several years.
But just because I wasn't dieting, didn't mean I wasn't conscious of my diet. The only reason I didn't continue gaining into infinity, is because I did focus on eating healthfully most of the time. I didn't eat less, but I did eat differently. I also exercised - not so much by going to the gym, but by doing so many of the things I didn't let my dieting self do. Going shopping just for fun, not because I needed to. Doing all the fun, active things I didn't think fat girls should do (at least in public) like going out with friends, dancing, swimming more...
There are just too many variables to account for weight and weight pattern differences between people, which is why I believe trying to model your behavior after someone else is usally futile.
Last edited by kaplods; 03-06-2014 at 04:50 AM.