Gorillas digestion is based primarily on fermentation of plant fiber, which is why they have a huge gut. Humans have an acidic stomach environment which doesn’t digest fiber at all. A small amount of fermentation happens in the human gut, but it can only produce a few calories a day.

Evolution has changed us considerably in the last couple million years.

We may be closely related genetically to gorillas, but our digestion is probably closer now to a dog’s than a gorilla’s.