You know the circus performer who spins the plates in the air you know, and he'll spin six or seven plates in the air? Acting sometimes is kind of that guy spinning all those plates in the air but in your head and in your body. ↗
While weight loss is important, what's more important is the quality of food you put in your body - food is information that quickly changes your metabolism and genes. ↗
You have to contort your body in a certain way to hit a low note. When you're on film, you can't. So you do, in a sense, get to hide behind your voice, which is nice. ↗