Physical activity (PA) is being increasingly promoted in children in an attempt to curb the rising epidemic of childhood obesity and its future consequences of obesity and cardiovascular diseases in adulthood. Although many reviews and guidelines have been published regarding PA in children and adolescents, none have specifically focused on the influence of intensity of activity on the crucial health aspects of fatness and cardiorespiratory fitness. Therefore, we conducted an online search for pertinent literature and reviewed 25 studies for this purpose. We found that there were limited studies that assessed the influence of 'intensity' of PA on health parameters, and there was considerable inconsistency in defining the thresholds for moderate (MPA) and vigorous (VPA) levels of PA. Collectively, we concluded that VPA is a significant predictor of fatness and significantly correlated to fitness. The association between the intensity of PA and cardiorespiratory fitness is more obscure compared with fatness because of limited studies and the varying conclusions made by them. However, decreased adiposity and increased aerobic capacity have been observed with participants who spent more time performing VPA. Further research needs to be undertaken to arrive at uniform thresholds for defining MPA and VPA and to obtain the exact dose of VPA and MPA, individually, to increase aerobic fitness and decrease adiposity.