Just to correct you, 7 days or thereafter on water-only will not result in what you refer to as "starvation-mode".
Starvation is a physiologically destructive process, where ones food reserves have become exhausted and the body then begins to feed on itself: this can last anywhere up to 50 to 60 days on water-only.
Fasting on water-only however, is a physiologically constructive process that continues while food reserves last, and preserves the integrity and health of the vital organs, whilst simultaneously healing and cleansing the body.
Hereward Carrington PhD has well summed up the matter in these words: "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."