In the present viewpoint, the authors provide an overview of the current evidence supporting the positive influence of practicing physical activity regularly and improving physical fitness, mainly cardiorespiratory fitness and muscular strength, on metabolic and overall health. The evidence on this regard is strong and consistent, and in the different age groups. Likewise, enhancing cardiorespiratory fitness by means of physical activity has the potential of attenuating the negative effect of obesity on future health, as well as improving the prognosis of the metabolically healthy obesity phenotype. Collectively, the existing evidence strongly supports the recommendation of being active and enhancing cardiorespiratory fitness and muscular strength as a powerful public health strategy.