Objective: Inflammatory processes contribute to disease pathways and may be affected by behavioral lifestyle factors. The relative contributions of fatness and cardiorespiratory fitness to inflammatory factors remain unclear. The present review examines the hypothesis that the association between fitness and inflammatory factors is independent of fatness.
Methods: Data were examined from 40 observational studies on the association between fitness/physical activity and inflammatory factors after making statistical adjustment for measures of fatness, and from 12 randomized controlled trials that considered the impact of improved fitness and weight loss.
Results: Two thirds of the observational studies report an inverse relationship between inflammatory factors and fitness after adjustment for fatness. Evidence from randomized controlled trials does not consistently support the hypothesis. Inconsistencies in the literature may be related to various factors such as age, gender, and disease status.
Conclusions: Both fitness and fatness appear to contribute to inflammatory factors, although it is unclear whether fatness is a mediator or if both fitness and fatness share the same causal pathways. Lifestyle interventions for primary prevention in the general public should therefore focus on both increasing physical activity and the prevention of excess adiposity, although the optimal exercise dose and body composition for preventing chronic inflammatory processes is not well established.