The symptoms of starvation are given in detail. Cite textual evidence.

From the text:

Starvation is not a pleasant way to expire. In advanced stages of famine, as the body begins to consume itself, the victim suffers muscle pain, heart disturbances, loss of hair, dizziness, shortness of breath, extreme sensitivity to cold, physical and mental exhaustion. The skin becomes discolored. In the absence of key nutrients, a severe chemical imbalance develops in the brain, inducing convulsions and hallucinations. Some people who have been brought back from the far edge of starvation, though, report that near the end the hunger vanishes, the terrible pain dissolves, and the suffering is replaced by a sublime euphoria, a sense of calm accompanied by transcendent mental clarity. It would be nice to think McCandless experienced a similar rapture.