There are some animals which hibernate - undergoing a period of winter sleep. Their metabolism is slowed down and they take no food for long periods of time. Bats, mice, hedgehogs, woodchucks, toads, lizards, snakes, flies, wasps, bees, bears, crocodiles, and alligators are among those that undergo some degree of hibernation. True hibernation is a dormant state of existence accompanied by great diminution of respiration, circulation, and metabolism.
Aestivation is a similar process which occurs in the summer time, and quite obviously these are not cold blooded animals. An example is the tenree of Madagascar. This climatic dormancy requires that the organism makes a variety of gradual physiological and biochemical adjustments that apparently correlate with temperature, light, and food scarcity.
The theory that "the sick must eat to keep up their strength" is inappropriate at times. It must be very unpleasant to many to see long established customs broken and long cherished prejudices set at naught even when a great good is to be achieved. There has been much contention in the scientific field about whether or not fasting is beneficial to one's health that fasting can do wonders for the human body. Fasting is an integral part of many of the major religions including Islam, Judaism and Christianity. To advocating fasting as a means of physiological rest and its physiological effects are as beneficial as the spiritual promoted by these religions, surely, should also be associated with physical, mental, emotional, and sensory rest so far as practicable. There are studies on fasting effect on human's body that prove the body rids itself of the toxins that have built up in our fat stores throughout the years. The body heals itself, repairs all the damaged organs during a fast. And finally there is good evidence to show that regulated fasting contributes to longer life.
In animal world, tadpole during its period of transformation to a frog, a number of fishes especially the female of the Cichlidae, they do fast during their breeding season. Penguins and the male goose are the only birds fasting during the mating season. Alaskan fur seal bull is the best known example of fasting by a mammal during the mating season. So is the sea lion during the mating season. There are many snakes do fast at times - that eat only at long intervals. Then there are marine iguana, seashore lizard of the Galapagos Islands which are apparently fasting in captivity.
So, why not us Moslems practicing the fasting for a whole Ramadhan month for god sake? Yes surely we can do it. It is , although hard initially, still a universe verity.