The aircraft’s provisions were gone within about ten days. What remained was the snow around them and the bodies of those who had died.
The decision that the survivors then faced has been discussed, analyzed, and argued about in the five decades since. It was not a hasty decision made in a moment of desperation. The survivors deliberated. They talked about it over days. They considered their options, which were essentially none: there was nothing at that altitude that could be eaten. The only source of nutrition available to them was the bodies of those who had died in the crash.
Several accounts of the deliberation survive from multiple survivors. The initial resistance was strong and rooted in cultural, religious, and psychological prohibitions that all of them carried. They were Uruguayan Catholics, raised in a framework that made the idea of consuming human remains deeply transgressive. They thought about how their families would react. They thought about whether God would condemn them. They thought about whether the people who had died would have wanted this.
Roberto Canessa has described, in his memoir and in interviews, the extended internal struggle he went through before he was able to participate. He was a medical student; he understood the nutritional logic more clearly than some of the others. He also felt, perhaps more viscerally than others, the weight of what was being proposed. He walked away from the group, sat alone, and eventually came back. He has said that what broke the barrier for him was reframing the act in terms of gift: the people who had died had, by dying, left behind something that could keep others alive. Using that resource was accepting a gift, not committing a transgression.