There is one place to eat on Gorgona: the park cafeteria, which serves three meals a day at fixed times. Cooking and open fires are not permitted anywhere on the island, and there is nowhere else to buy prepared food. The food is simple and filling — standard Colombian comida corriente — and the schedule is non-negotiable.
For stays of a day or two this is perfectly fine. For longer stays, bring your own snacks. A few items of dried or packaged food will make the days between meals more comfortable, especially if you are out on a full-day trail.