Each day they get 1500 cal each. But they can steal or horde. Then the weak will be starving which is okay for a few days. They would be provided with unlimited water, tea and coffee with no sugar so they don't die of thirst. There would also be edible greens on the island for the savvy ones. lol  Maybe penalties would be if someone stole they have to go without and give their portion to the person they stole it too.