I've learnt a lot about myself, food, and healthy eating in the last few years while trying to lose weight. Some of them were things that I kind of always knew at the back of mind, but let them stay at the back of my mind. Some are things that I learnt from other people who have gone through the same kind of thing, through online communities, and literature.
I was just thinking, a couple of days back, about how my friends and I used to eat at McDonald's all the time and not think about it. Now I've been reading up about the ingredients they use, the kind of oil they fry in, and the nutritional stats of their food. I still eat there occasionally, but only occasionally, and only because they are sometimes the only choice at freeway rest stops. I do like their barbecue chicken wraps a lot, though.
I've learnt that it always helps to know what you're eating and what goes into it in what quantity. If you're buying packaged food in India or another country where they don't always print the nutrition information on the package, they probably do still have a list of ingredients in there. Ingredients are generally listed in a logical order - the one listed first is the one that is used in the largest amount. That list does generally give you a pretty good idea about things.
I've learnt that the first bite of dessert tastes the same as the last bite. Unless it's a layer cake. What that means to me is that I don't need to eat a whole brownie, a whole bar of chocolate, or a whole cup of ice-cream to satisfy a craving. I can eat whatever I want, as long as I can practise portion control.
I've learnt that the pleasure derived from eating comfort food is a momentary and fleeting pleasure, while the pleasure of being able to fit into a size 8 (sometimes even 6!) top after years of wearing unmentionably large sizes is a pleasure that is a lot more permanent.
I've been too large for too long. When I go out shopping, I will sometimes still pick up a size "L" shirt to take into the fitting room, realize that it is too big, try on the medium, and finally settle for the small. It's a little more time consuming if they have the numbered sizes, because that means that I work my way from 12 all the way to 6 or 8. But I'm getting used to it. And it's a great feeling.