A starvation diet is any diet that you take in less calories or less nutrition than you use up each day. The body does not make up the difference and starves to death. If you follow the fasting principles however your body will supply it's own nutrition by feeding off it's own reserves. Don't ask me why, that's just the way it is.
As an example (true story) there were once three hunters having a bad season. All they could catch was rabbits over a period of about 9 months. They all died of starvation because the rabbits were missing a vital element of nutrition- I can't remember what. The point was they died of starvation with their bellies full.
If you feed your body it expects full nutrition. If you fast your body completely it will very efficiently conserve what it has and live off the stores while maintaining and repairing it's flesh and organs as needed.