Does serum albumin mediate the association between vigorous physical activity and waist circumference? Evidence from NHANES

Background The biological mechanisms underlying the beneficial effects of vigorous physical activity on abdominal obesity remain incompletely understood, and the potential mediating role of serum albumin has rarely been investigated. Methods We analyzed data from 4,882 U.S. adults in the National Health and Nutrition Examination Survey (NHANES) using multiple linear regression, mediation analysis, and survey-weighted sensitivity analyses. Results After adjustment for potential confounders, vigorous physical activity was significantly associated with serum albumin (β = −0.066, SE = 0.011, P < 0.001). Serum albumin was inversely associated with waist circumference (β = −13.42, SE = 0.71, P < 0.001), whereas vigorous physical activity remained positively associated with waist circumference coding (β = 4.11, SE = 0.56, P < 0.001). Mediation analysis showed a significant indirect effect through serum albumin (average causal mediation effect = 0.885, 95% confidence interval: 0.596 to 1.187, P < 0.001), accounting for approximately 17.7% of the total association. Survey-weighted sensitivity analyses yielded consistent results. Conclusions These findings suggest that maintenance of protein metabolic homeostasis may represent an additional biological pathway through which physical activity promotes metabolic health and may identify a potential therapeutic target for future interventions against abdominal obesity