Hunger is a feeling of discomfort or weakness caused by a lack of food.

Thirst is the feeling of needing to drink something. It occurs whenever the body is dehydrated for any reason.

After an extended period of time, going without food and water, all humans eventually get hungry and thirsty literally!

As used in this passage, hunger and thirst are used as part of a metaphor intended to illustrate a person who has a strong desire for something (in this case righteousness), as likened unto a person who is hungry or thirsty.

1. I am the living bread:

Bread is something which is made from grain, typically wheat. Jesus was certainly not bread, at least not in the traditional sense of the word, he was a man (Mark 15:39, John 8:40; Acts 2:22; Romans 5:15).

2. "...which came down from Heaven"

[ Ref: For I Came Down From Heaven (John 6:38)  ]

3. If any man eat of this bread (Jesus):

To eat implies to consume or intake something "eatable" by means of your mouth. (People did not literally eat Jesus' flesh ).

4. He shall live forever:

Excluding Christ, there is no evidence that anyone (human or non-glorified) is still alive from the time this statement was made by Jesus. The Bible declares that Man is appointed to die, at least once (Heb 9:27) and after that the judgment, which has not yet taken place.

The Tree of Life (man's first Eternal Life opportunity) was removed from the garden of Eden thousands of years ago (Gen 3:22, 23, 24).