Losing weight is about eating as little as possible, and limiting calories and carbohydrates. Maintaining weight, on the days you are eating carbs, is mostly about limiting fat. When you want to lose weight, you’ll be less hungry if you limit carbohydrates as much as possible, and you’ll lose weight fastest if you limit calories as much as possible. When you want to maintain, you’re in damage control mode. Maintaining weight (when you are eating carbs, which facilitate fat storage) is best done by limiting fat. Fat has 9 calories per gram, compared to 4 calories per gram for protein and carbohydrate.