If they differ, the weight starts to increase or decrease correspondingly. This simulation is obviously overly simplistic. Similarly, overeating for too long increases the weight to improbable proportions. The weight comes off very slowly, even on a starvation diet. This illustrates another of those little facts we might like to forget.
Exercise is critical to weight loss.
Note that there is nothing in this balance simulation that causes the level of the pool to stay at any particular level. It could be anything. In many physiological processes, the output reflects the size of the pool itself. In such a case, the pool will reach a new equilibrium for each different level of input. Go to the next simulation to see this in action.