star wars - How does a sarlacc gain any energy if it keeps victims alive for a thousand years?

When eaten by a sarlacc, according to C-3PO,

In his belly, you will find a new definition of pain and suffering, as you are slowly digested over a thousand years.

I imagine that keeping a victim alive for a thousand years takes much more energy than is available to the sarlacc from the body of the victim. Thus, keeping victims alive for so long would seem to be a net loss of energy for the sarlacc.

Is there a canon answer to resolve this conundrum? Did the sarlacc have another energy source (for example, ability to harvest sunlight)?

Answer

The very short answer is that the Sarlacc gains energy from digesting non-sentient creatures (womp rats, eopies and so forth) and then uses that energy to torture its sentient victims, gaining a measure of telepathic enjoyment from their agony.

In fact, it likes their pain so much that it expends energy in keeping them alive so that it can keep torturing them almost indefinitely.

The mature Sarlacc, however, does have mobile tentacles and legs but has adapted its legs as anchor roots. Scientists currently believe the Sarlacc is an animal, much like sponges and anemones are animals. Because it lives in the middle of the desert, the Sarlacc does not feed often, but because of its highly efficient digestive system, it doesn't need to. Its body preserves food for incredibly long periods of time, digesting it slowly and storing it until the Sarlacc needs nourishment. Unfortunately, the victim often remains alive for much of the time, in part sustained by the Sarlacc's internal nutrients.

One of the prevailing rumors about the Sarlacc is that the creature is mildly telepathic and actually gains knowledge and sentience from victims as it consumes them, sometimes over thousands of years, depending on the species of the meal. Some data Senior Anthropologist Hoole secured from the bounty hunter Boba Fett have confirmed this.

Fett's helmet recorder was running, apparently, during a period in which he was trapped inside the creature. When I sat down to study the tape, I was horrified. Not only was it clear to me that the Sarlacc was sentient, but it enjoyed torturing those it was digesting. Fett's actions and responses plainly indicated that the creature manipulated the thoughts of its victims, and even kept their intelligence stored in its memories so it could savor their pain at another time.

The recordings also showed a more anemonelike physical structure than most scientists have believed, and the secretion of some digestive enzyme that might be the cause of their hallucinogenic power over their victims. This theory was supported by the fact that Fett could plainly be seen reacting to stimuli that were not there.

_{^{The New Essential Guide to Alien Species}}