It's counter to well over 50 years (if not more) of medical evidence and experience with sustainable weight loss. Look up the Minnesota Starvation Experiment -- used to study the effects of long-term starvation among WWII POWs and concentration camp survivors. This involved six months of semi-starvation -- at 1500 cal/day. http://en.wikipedia.org/wiki/Minnesota_Starvation_Experiment
Fewer than ~1200-800 cal/day is generally considered "VLCD": very low calorie dieting. If macronutrients and micronutrients aren't very carefully controlled, the body is essentially eating itself in slow motion. And odds are very good you wouldn't be able to exercise much if at all at 500 cal/day.
It's counter to well over 50 years (if not more) of medical evidence and experience with sustainable weight loss. Look up the Minnesota Starvation Experiment -- used to study the effects of long-term starvation among WWII POWs and concentration camp survivors. This involved six months of semi-starvation -- at 1500 cal/day. http://en.wikipedia.org/wiki/Minnesota_Starvation_Experiment
Fewer than ~1200-800 cal/day is generally considered "VLCD": very low calorie dieting. If macronutrients and micronutrients aren't very carefully controlled, the body is essentially eating itself in slow motion. And odds are very good you wouldn't be able to exercise much if at all at 500 cal/day.