Physical sporting activity impact on long-term BMI trajectories in adults: a longitudinal observational study

Background This longitudinal study examines the relationship between self-reported physical activity intensity, measured via Metabolic Equivalent Task (MET) scores, and body mass index (BMI) trajectories over a five-year period in a representative Dutch sample. Using annual data from the Longitudinal Internet Studies for the Social Sciences (LISS) panel (N=6,337), we analyzed how changes in energy expenditure due to sporting activities influence BMI, while assessing moderating effects of age, gender, and baseline BMI. Methods MET is significantly associated with BMI, accounting for approximately 2% of its variance. Longitudinal analyses revealed that yearly changes in physical activity levels had a comparably smaller impact on BMI. This relationship was particularly attenuated among individuals without obesity and older age. However, more substantial effects emerged in individuals with obesity (BMI≥30), where adopting activities with a 10-point MET value was associated with BMI reductions of 0.45-0.81 points. Although these effects may be considered as modest in magnitude, their clinical relevance is underscored by the study design, in which BMI and sporting activity assessments have been several months apart, suggesting sustained effects rather than transient fluctuations. Results Our findings provide a representative estimate of sporting activities impact on BMI. For healthcare practitioners, these results assist evidence-based counselling by establishing realistic effectiveness expectations of sport activities. Moreover, the results emphasize the need for tailored, weight-status-specific approaches to physical activity recommendations. In particular for obese and older populations, more comprehensive weight management strategies are required to produce substantial effects.