The Genesis account not only tells us that God created man in His own image, but it also tells us what God instructed man to eat.

Gen 1:27  So God created man in His own image; in the image of God He created him; male and female He created them.
Gen 1:28  Then God blessed them, and God said to them, “Be fruitful and multiply; fill the earth and subdue it; have dominion over the fish of the sea, over the birds of the air, and over every living thing that moves on the earth.”
Gen 1:29  And God said, “See, I have given you every herb that yields seed which is on the face of all the earth, and every tree whose fruit yields seed; to you it shall be for food.

When God created the world, it is clear that He planned for mankind to be vegetarian.  Not only was mankind to be vegetarian, but so also were the animals.

Gen 1:30  Also, to every beast of the earth, to every bird of the air, and to everything that creeps on the earth, in which there is life, I have given every green herb for food”; and it was so.

All this was deemed by God to be very good.

Gen 1:31  Then God saw everything that He had made, and indeed it was very good. So the evening and the morning were the sixth day.

However, after the flood, God said meat could be eaten.

Gen 9:3  Every moving thing that lives shall be food for you. I have given you all things, even as the green herbs.

At what point did this change happen?  After the flood?  Or, perhaps after Adam and Eve sinned in the garden of Eden?  God made tunics of skin to clothe them.  Did God kill an animal to do this, and if so, was the carcass eaten?

Gen 3:21  Also for Adam and his wife the LORD God made tunics of skin, and clothed them.

The Bible doesn’t provide enough information to answer these questions.  However, the answer to the question, “Were Adam and Eve vegetarians?” is, yes, they were initially, but they may not have been all their lives.