Those penalties are less direct, however. It makes it harder for people to draw the immediate correlation between the two. Hunger drove a sufficient level of fitness to obtain food to satisfy hunger (not in the sense of encouraging the person to do push-ups, but it encouraged them to literally move and obtain sustenance, ideally before they were too weak to do so). Unhappiness doesn't lead to movement until thought and reason are applied to recognize the causal or correlative nature of unfitness and poor mental health.