Actually, anything under 1200 calories (roughly, since everyone is different) is considered borderline starvation, and your body goes into surivival mode. You literally shock your system, and your metabolism drops. You could say, you need to eat to lose weight. You just have to eat right. If you eat 1600 calories a day for a month, you'll lose more than if you eat 1000 calories a day for a month. What's even worse is that when you go back to eating normal (because NOBODY is going to stick to a 1000 cal/day diet) you will begin to gain the weight back because your metabolism has been dropped. You are correct that you burn calories while you sleep, especially after a day involving exercise. Your body is always burning calories, just trying to maintain full function. That's thermogenics. If you have a steady diet (good or bad), and you consistently maintain your weight, you can find your average daily caloric intake, which is a great way to establish a baseline, and go from there. Maybe you maintain at 4000, maybe you maintain at 2500, but you should never drop your intake to below 1200 calories. I wouldn't even go under 1500.
A very common misconception is that you would lose more weight with the less you eat and the more you exercise. This is where people get very frustrated, because they'll eat next to nothing for a couple weeks or longer before they finally give up. Maybe they lose a few pounds, but most likely the body has started to eat away at muscle, which is the last thing you want (because as you stated, muscle is our metabolism). I would think that boxers would become thin through training and a good diet, not necessarily through starvation. Any active athlete should be eating much more than that, since they need to feed their muscles and have fuel for their lifestyle. If Floyd Mayweather was on this diet, he'd be looking like a starving Ethiopian in no time. Ok, I went on probably too much, but I am just trying to clear this up and see where you're coming from. What do you mean by Nazi studies?