Fitness or fatness—which is more important for cardiovascular risk?

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There is no question that the epidemic of obesity is resulting in increased risk for cardiovascular disease across the population of children and adolescents. However, there is still much to learn about the mechanisms of this increased risk. One important question relates to the relative role of fitness and fatness. Are there some children who are at lower risk, despite being overweight, because of increased fitness?

In this issue of The Journal, two articles report on studies that begin to evaluate elements of these relationships. Allen et al studied overweight middle school children. They found that both percent body fat and V02 Max were associated with the level of fasting insulin. However, particularly in boys, the relationship of cardiorespiratory fitness to fasting insulin was stronger than the relationship of percent body fat and fasting insulin.

Rizzo et al examined the association of physical activity and cardiorespiratory fitness with a clustering of metabolic risk factors. They found that cardiorespiratory fitness was more strongly correlated with metabolic risk than total physical activity. However, body fat seems to play an important role in the association of cardiorespiratory fitness and metabolic risk.

Both studies emphasize the role of fitness, but also support the role of fatness. This would seem to put physical activity in an important role. However, it should be emphasized that fitness is only partially determined by physical activity. Fitness also has an important genetic component. Further research is needed to evaluate developmental and other aspects of these interrelationships.