In Chrono Trigger, the Enertron is a machine found in several locations in 2300 AD. It restores HP and MP, but displays the message, "But you're still hungry." It is implied that in the absence of any food, the survivors of the Day of Lavos rely on the Enertron for survival until Marle gives them seeds to grow, insisting that the Enertron won't last forever. Presumably, the Enertron revitalizes diseased, malnourished, or dying tissue, allowing the inhabitants of the domes to survive despite a lack of food.
In Chrono Cross, an Enertron can be found in the Dead Sea, near Nadia's Bell. It also displays the message, "But you're still hungry..."
In the Nintendo DS remake of Chrono Trigger, the message displayed is "But you're just as hungry as before."