Vegetarian Diet

Can Christians become a vegetarian? It depends on the motivation.
Now the Spirit expressly says that in later times some will depart from the faith by devoting themselves to deceitful spirits and teachings of demons, through the insincerity of liars whose consciences are seared, who forbid marriage and require abstinence from foods that God created to be received with thanksgiving by those who believe and know the truth. (1 Timothy 4:1-3 ESV)

In the beginning, men and animals are vegetarian.
And God said, "Behold, I have given you every plant yielding seed that is on the face of all the earth, and every tree with seed in its fruit. You shall have them for food. And to every beast of the earth and to every bird of the heavens and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food." And it was so. (Genesis 1:29-30 ESV)

After the flood, men are allowed to eat meat.
The fear of you and the dread of you shall be upon every beast of the earth and upon every bird of the heavens, upon everything that creeps on the ground and all the fish of the sea. Into your hand they are delivered. Every moving thing that lives shall be food for you. And as I gave you the green plants, I give you everything. (Genesis 9:2-3 ESV)

During the reign of Christ in the Millennium, carnivores will become herbivores. There will be no poisonous animals and everyone will become environmentally friendly. But will men become vegetarians again? It was not mentioned, but the fattened calf is mentioned.
The wolf shall dwell with the lamb, and the leopard shall lie down with the young goat, and the calf and the lion and the fattened calf together; and a little child shall lead them. The cow and the bear shall graze; their young shall lie down together; and the lion shall eat straw like the ox. The nursing child shall play over the hole of the cobra, and the weaned child shall put his hand on the adder's den. They shall not hurt or destroy in all my holy mountain; for the earth shall be full of the knowledge of the Lord as the waters cover the sea. (Isaiah 11:6-9 ESV)
The wolf and the lamb shall graze together; the lion shall eat straw like the ox, and dust shall be the serpent's food. They shall not hurt or destroy in all my holy mountain," says the LORD. (Isaiah 65:25 ESV)