How long does it take your body to break down your body fat from anorexic behaviors? ex. eating 50% recommended calories, 15% body fat, male, 180 lb

Bad idea: (semi) starvation will stress breakdown of protein for several weeks. Better to increase calories, protein intake, and increase calorie output (physical activity). Nothing to extreme. See md, rd, and therapist (or psychiatrist).

Planning a diet?: You're actually describing a rigorous weight-loss diet such as athletes undertake to make weight or fitness guys to "get ripped"; it would be an anorexic behavior if it became an obsession or you were likely to hurt yourself. You're at your physical prime and if you can adopt a fitness-focused lifestyle instead of episodic diet, it's be great. Your physician can help.