Next time, please give the context. There's more than one meaning, depending on how the phrase is used; and it may have either positive or negative meanings.
The sexual meaning seems to interest the most people. That does not reflect well on us, and in normal speech among normal people, it is the least common.
The most common meaning is that somebody is so cute that, if he she were candy or a cookie, the speaker could not resist the temptation to eat the person described. Sometimes "gobble" is used instead: You are so cute, I could just gobble you up! ("Metaphorical" would have been a much better term than "psychological.")
The third meaning could have been explained better: Letting yourself obsess over resentment or bitterness can use your time and energy to the point that it hurts your mental or even physical health. You could compare an obsession over, for example, some insult, to a predator such as a wolf or a bear. "If you don't let go of your bitterness, it will eat you up." Another way of saying it is that "it will consume you."