In answer to your question.......
Q. Where is the line between fasting and starvation in terms of the body's interpretation occurs then? What are the physiological differences??
1. Fasting is the feeding from internal food reserves which sustains the vital organs, and which is an extremely beneficial process that redirects the energy that would have been used in digestion, (the most energy consuming task of the body) into the massive acceleration of healing and cleansing. This can safely be carried out for many weeks in most cases. There are very few contraindications.
2. Starvation occurs when the these food reserves have been depleted (or nearly so) being marked by the genuine return of hunger, and where the body will then turn to feed from its vital organs, unless refeeding takes place.
Fasting is a beneficial process leading to good health, the elimination of toxemia, and healing.
Starvation being a destructive process leading to death.