Background: Dietary supplements are consumable products that contain ingredients intended to supplement the diet. Dietary supplements are marketed to the public for various reasons, including improving one’s body weight profile, energy, nutrition, sleep, beauty, athletic performance, mental and physical health, and disease risk. The evidence supporting many of these marketing claims is sparse. Furthermore, the extent to which dietary supplement use for a specific purpose influences physical activity (PA) in adult populations is unknown. The aim of this study was to examine the association between dietary supplement use for gaining muscle and PA in U.S. adults. Methods: Adults 20+ years of age from the 2017-2020 (pre-pandemic, 3.2 years) National Health and Nutrition Examination Survey (NHANES) were used. Participants were categorized into one of three supplement groups: uses a supplement to build muscle (USBM), uses a supplement for other reasons (USOR), or non-supplement user (NSU). PA variables included work (VWPA, MWPA), recreational (VRPA, MRPA), transportation (TPA), sedentary time (SED), moderate-to-vigorous PA (MVPA), met PA guidelines status (METPA), and physical inactivity (PIA). ANOVA and regression analyses were used while controlling for age, sex, race, income, and BMI. Results: Bivariate analyses showed that USBM adults had significantly greater VRPA (Mean = 168.6 min/week vs. Mean = 65.8 min/week, p = .0034), MVPA (Mean = 481.3 min/week vs. Mean = 228.5 min/week, p = .0019), METPA (Mean = 53.9% vs Mean = 38.5%, p = .0071), and significantly lower PIA (Mean = 34.8% vs Mean = 45.7%, p = .0275), than their counterparts, respectively. In the fully adjusted model predicting MVPA, USOR (b = -203, p = .0055) and NSU (b = -252, p = .0006) groups had significantly less MVPA than USBM. Furthermore, in the fully adjusted model predicting METPA, USOR (OR = 1.38, 95% CI: 1.18 – 1.61) and USBM (OR = 2.44, 95% CI: 1.47 – 4.05) groups had significantly greater odds of METPA, as compared to NSU. Finally, the supplement group-by-sex interaction (p = .0290) indicated that males (Mean = 561.7, SE = 93.3 min/week) in the USBM group had significantly greater MVPA than all other supplement groups, including USBM group females (Mean = 244.1, SE = 49.8 min/week). Conclusion: Results from this study indicate that U.S. adults taking supplements to build muscle report significantly more recreational PA than other supplement or non-supplement users. Furthermore, males taking supplements to gain muscle report significantly more MVPA than all other adults taking and not taking supplements.

nutrition, supplements, physical activity, MVPA, epidemiology, population health