The suggested food pyramid suggests mostly grains and carbs, which spike insulin and trigger the satiety response. It's much easier to eat two thousand calories of protein and fat, than two thousand calories if carbs. Also fat is more than twice as dense in calories than carbs.
Combining this with the human body's capacity for adaptation (it becomes gradually easier to eat bigger meals), eating two days worth of calories in even one sitting is not that difficult.
Combining this with the human body's capacity for adaptation (it becomes gradually easier to eat bigger meals), eating two days worth of calories in even one sitting is not that difficult.