Not only is meat regarded as sinful, and unnecessary for the sustenance of life, but meat is simply not considered "food" as per Jain reckoning, which evidently takes for granted that human beings must never consume it (whether hungry or not).
Meat is but one class among twenty-two unedible substances. In summary, however, it can be discerned that each of these substances are forbidden for some or all of the following reasons:
Meat eating is strictly forbidden. The discussion of abdication of meat eating etc. is found in the context of real-conduct after the discussion of Right-belief and Right-Knowledge. In the context of the vow of non-injury, Acharya Amritchandra has at length and with forceful logic emphasised renunciation of meat eating. There total prohibition of uncooked as well as cooked meat of naturally died beasts, meat obtained after killing, meat of vegetarian and non-vegetarian beasts etc., is described at length.
A few original verses of Purusharthasidhyupaya, throwing light on the above topic are as follows: "Without killing creatures, production of meat is not possible. Therefore, injury is inevitable for meat-eaters. Although it is true that meat can be obtained naturally from died bullock and buffalo, but there in too incessantly creatures of the same genus are born and by their churning and destroying injury takes place. He who eats, even touches, cooked, uncooked or any other kind of meat-piece, annihilates many genuses of the mass of Jivas."
According to Jain definition, flesh of the body of mobile beings is termed meat. Right from two-sensed beings upto five-sensed beings are called mobile beings.
The production of meat takes place not only on killing of mobile beings but incessantly innumerable mobile beings are being born in meat. Therefore by eating meat not only the vice of injury to that particular Jiva is involved who has been killed, but also the crime of killing innumerable creatures is also committed who are continuously born in it. Assuredly meat eating is the cause of several diseases notably in recent times "mad-cow" disease.
Man is by nature vegetarian only. Acharya Amritchandra and Samantbhadra prohibited meat eating at length. Meat-eating impure, immoral, injury causing and the cause of countless miseries.