Hello Wheatgrass,
I'm not sure where you've received your information but fasting does not become starving at ketosis.
Ketosis is the result of the body switching from an external food source and the use of glucose as fuel to ketones via fat metabolism: ketosis is the actual process by which the body burns fat as a prime fuel source. Some glucose is still required by the Brain and where its needs are met even on the most protracted fast.

In answer to the posters original question fasting ends when the bodys food reserves have expired or almost expired and which time genuine hinger will appear to prevent starvation. Fasting is constructive whereas starvation is destructive.
Even the overweight individual can be literally starving as their nutritional status is devoid of the real sustenance it needs. Shelton referred to such a diet as living from "foodless foods".

Hereward Carrington so accurately stated that........

"Fasting is a scientific method of ridding the system of diseased tissue, and morbid matter, and is invariably accompanied by beneficial results. Starving is the deprivation of the tissues from nutriment which they require, and is invariably accompanied by disastrous consequences. The whole secret is this: fasting commences with the omission of the first meal and ends with the return of natural hunger, while starvation only begins with the return of natural hunger and terminates in death. Where the one ends the other begins. Whereas the latter process wastes the healthy tissues, emaciates the body, and depletes the vitality; the former process merely expels corrupt matter and useless fatty tissue, thereby elevating the energy, and eventually restoring the organism that just balance we term health."

Chrisb1.