Because most of us don't get much exercise, we have to change our diets. Before I broke my neck, I ate startling amounts of food. My metabolism was such that I would burn up the calories and not gain any fat. I can't eat like that anymore, without putting on lots of weight. I know, I tried it.
The way I've lost weight and kept most of it off involves basically three different things.
One, I reduced the portions I eat. Very often I'll eat only half of a meal at a restaurant and take the rest home. We are taught from a young age to eat everything on our plate. That's helpful for growing boys and girls, but it's not great for adults, especially sedentary adults. It is difficult, though, to break that subconscious, ingrained mindset as we get older. It's much better, though, to eat small amounts several times throughout the day (not just three meals).
Two, I now pay attention to what I eat. I learned from one of my best friends in the world that we need to eat protein and carbohydrates together. If we just eat carbohydrates our bodies have an insulin response, which then turns to fat. If we eat just protein, our bodies have a glycogen response, which also turns to fat. The art of "food combining" is much more effective than I ever imagined. I don't eat the huge portions I did in college, when I played rugby and my metabolism was set to rocket-speed. But I still am satisfied – I just eat smarter. I stay away from calorie-dense foods and processed sugar (for the most part).
Three, I try to increase my metabolism as much as possible. I don't like coffee, so I didn't get much caffeine. It might sound crazy, but now I have a sugar-free Red Bull before every meal. It helped me to lose a lot of weight once I started my concentrated effort to do so. And it helps me in "maintenance mode." I'm trying to replace some of the Red Bull with more diet green tea, as a metabolism enhancer (also a good source of antioxidants). Another thing you can do to speed up your metabolism is eat small amounts several times a day, like mentioned above. If you starve yourself for long periods of time, when you do finally eat, your body thinks it needs to store that energy, so it turns the food into fat. If you eat small, several times, your body's metabolism naturally increases, and you lose weight, or maintain.
I'm not a calorie counter. And I still need my butter. But it helps to pay attention and get familiar with what foods are the most fattening. I still indulge in the occasional ice cream, or my brother's crab rangoons! But I don't get too carried away. It's just not worth it.
If we give up and say to ourselves, "I'm just going to be fat because I'm in a wheelchair," we're starting down a dangerous path. It's a downward spiral of a lack of self-esteem and destructive behavior that keeps perpetuating itself, getting worse and worse. The fatter we get, the less self-esteem we have. With lower self-esteem, we get disgusted and figure there's no reason to keep up our appearance, so we engage in binge eating to placate ourselves, and make ourselves feel better ... temporarily. The worse our appearance gets, the more we lose the respect of others and respect for ourselves.
On the other hand, if you take control of your diet you'll feel better about yourself, and you'll actually feel physically better. The better you feel about yourself, the better you treat yourself, and then you get to feeling even better. It's an upward spiral on which to build. Try it; even just for a month. Be strict with yourself. You'll start to see results fairly soon. Whatever you do, don't give up on yourself. Don't let the wheelchair become an excuse. That's a dangerous proposition. Instead ... adapt and overcome!