Training based on your heart rate can address this concern. Muscle will be burned if you are under nourished. However, you can target fat by training in a specific Heart Rate zone.
Nothing will lose weight like starvation, but of course it is unsustainable. Don't think that to lose weight you have to lose muscle however. By varying your training and eating appropriately you can lose fat and gain muscle.
Now, for body building purposes, maybe not, as I think they bulk up and go lean consecutively. I have had success, however, gaining muscle and losing fat by using weight lifting and long low intensity cardio workouts. Eating appropriately after both.
My uncle was on this program where he ate an absurd diet. There is no way I could have done it because I do like food and plan to enjoy it from time to time but the interesting thing was the exercise. I believe it was an hour walking at something like 2 mph. He had great success with it.
That's a good point on the muscle mass thing. I honestly don't care if I lose a lb. I know that I will, but that's not what is important. My goal is 190, even though I don't know if I will be able to get there. I am a fairly decent framed guy. I feel like if I get dow to 200 on the current program I will look pretty good and be in good shape. Those were my goals. The numbers are kind of secondary I guess. I think my "ideal" weight is like 170 or something which isn't going to happen with the way I'm built.
There are just some people who can't get as ripped as others. You can see that in the Insanity videos. Look, those guys are all in phenomenal shape but some just are more defined than others. I don't know anything about the ROTC, but a guy was talking to me about having to make measurements and his kid was having a heck of a time making them because of his body type and the fact that he just can't rid of that extra 10 lbs or whatever. Maybe someone will correct me but I think there are just those people who can't get that last little bit off without going to extraordinary measures.