“Physical fitness is not only one of the most important keys to a healthy body; it is the basis of dynamic and creative intellectual activity. The relationship between the soundness of the body and the activities of the mind is subtle and complex. Much is not yet understood. But we do know what the Greeks knew: that intelligence and skill can only function at the peak of their capacity when the body is healthy and strong.”- President John F. Kennedy

    

I think that this quote means that, having a healthy body results in having a healthier brain which then leads to higher intellectual capability. This results in overall health.