I'm no fan of claiming "thick" when a girl is fat. But I personally been fighting a weight problem my whole life, so I know it ain't easy. Think about it like this: what if you were addicted to a drug that you HAD to have to survive? I can go without eating for days at a time. But the problem is, just about every time you eat something when you're dieting, it doesn't fill you up, it just makes you hungrier, until you give your body plenty of what it REALLY wants, which is inevitably something high in calories. 20 lbs or celery sticks would make me hungrier with each bite, and only a big slice of cake or a burger would make me stop thinking about food for a while. And thinking about food wears on you, it only takes one moment of weakness or lost focus.
And claiming there is no "fat gene" is obviously wrong. You telling me, thin people are thinner because they know more about weight loss? You've clearly never had a weight problem. It's not a simple thing, you're talking about body chemistry, the way it effects your mind and perceptions here, your energy levels, all of that. Man, few years back I lost like a hundred pounds, had some health issues, gained it back. But I have had a thinner roommate since then who tried to give me advice on weight loss, man had never been on a diet or in a gym his whole life. Unlike me, he never had to think about staying thin, no point on educating himself about it.
It's not all genetics, but don't think that there "is no fat gene." By the way, I know how to lose weight because I have been educated on the subject, but knowing how to do something isn't the same as having the strength to overcome genetics or a mentality, whatever you want to call it.
