Can't say about your particular situation, but I think that, in general, our view of what is "normal weight" is very distorted due to the fact that most people

Can't say about your particular situation, but I think that, in general, our view of what is "normal weight" is very distorted due to the fact that most people around us are kinda fat. The same goes for exercising habits; people who don't move much often see twice a week jogging or something as a good amount of exercise. While it is certainly better than nothing and probably more than many people get, it's still much, much less than an average person exercised a hundred years ago by just living a normal life. A person who doesn't provide any kind of stimulus to maintain their muscle mass can have low BMI too much body fat at the same time.