Indeed, fasting or starvation is commonplace in the wild, but lets not confuse the two terms: fasting means living from ones food reserves in the absence of external nourishment, and a biological adaptation to accommodate for food scarcity in the prevention of starvation, when internal food reserves become exhausted (anywhere between 30 and 60 days and beyond in humans).
Fasting is a physiological and beneficial process, whereas starvation is a pathological and destructive one.
The central message of Natural Hygiene (a term coined by Shelton in conjunction Dr Robert Gross to distinguish this from "medical hygiene) is to "listen to ones body": drink when thirsty, eat wholesome food when hungry; sleep and rest when tired; an abundance of fresh air; warmth; exercise; judicious sunlight exposure and emotional poise and so on, and in proportion to bodily needs and demands will produce wellness and superior health which the body is constantly striving to achieve, and accelerated given those conditions and circumstances.
Fasting can therefore be voluntary or involuntary, so in the absence of hunger/appetite the body will suspend digestion for more urgent tasks; this is why we lose our appetite/hunger when sick or become injured, as this energy is diverted innately by the body into self-healing and cleansing.
We should also bear in mind that fasting per-se is a means to an end, and not an end in itself.
So fasting when well, and we have health in abundance, and appetite/hunger is strong, is superfluous or unnecessary.
Voluntary fasting such as an annual short fast to cleanse the body of accumulated exogenous toxins (pesticides, herbicides, and atmospheric pollution, is probably a wise "precaution" to keep toxemia to a minimum.
However, in most cases, if we are well and have health in abundance, a full quota of nerve-energy or life-force will allow the body to keep-up with its normal processes of nutrition and drainage, making the fast superfluous.
All of the above is the central message of Natural Hygiene borne out of the vast experience of the health pioneers dating from the early 1800's and Dr Isaac Jennings MD.