There's this book "A Treatise on the Yoga Philosophy" i saw some time ago that deals about how the yogis of india lived (1882).
If i recall correctly, it says that the indian sages used to observe the animals and imitate their lifestyles. i.e eating only rice and milk, breathing very little, etc.
IMO, this kind of practices should only be followed by really determined people who live a life of holiness and asceticism. We have to keep in mind that the physical necessities of each person has many variables, all consequence of their previous lifestyle. Some might need to eat meat, while other might live on nuts and milk. To change our current state is usually a long process of many years and sometimes many lives. I'll state the obvious and say that eating just enough, never becoming full, as well as a vegetarian diet, will in most cases lead to a longer and healthier life. But you should not go full new-age nutjob and try to feed on sunlight because it raises your vibrations and will take you to the 95th dimension of jupiter.