Relationship between Meeting Physical Activity Guideline Parameters and Body Mass Index (BMI) in Adults

Background: Physical activity (PA) and risk of obesity are inversely related in adult populations. However, the extent to which meeting different PA guidelines influence body mass index (BMI) is less known. The aim of this research was to examine how different PA guideline parameters affect BMI in adults. Methods: The Montana Behavioral Risk Factor Surveillance System (BRFSS, 2019) was used for this study. Four different PA guideline variables were used and included 1) 2-level aerobic PA (APA) (met APA or did not meet APA), 2) 2-level muscle strengthening activity (MSA) (met MSA or did not meet MSA), 3) 4-level PA (met both APA and MSA, met APA only, met MSA only, or met neither), and 4) 3-level APA categories (active, insufficiently active, or inactive). BMI was calculated from self-reported height and weight (kg/m2). Multiple linear regression was used to examine the effect of each PA guideline parameter on BMI while controlling for sociodemographic variables. Results: Findings showed that meeting the 2-level APA (slope (b) = -0.74 kg/m2, p < .0001) or the 2-level MSA (b = -0.75 kg/m2, p < .0001) guideline was associated with lower mean BMI. In the 4-level PA model, as compared to meeting neither guideline, meeting APA only (b = -0.58 kg/m2, p = .0119) or meeting both APA and MSA (b = -1.32 kg/m2, p < .0001) was associated with lower mean BMI. Meeting MSA only did not show significantly (p = .1748) different BMI from those meeting neither guideline. In the 3-level APA model, as compared to those categorized as inactive, those categorized as active (b = -0.91 kg/m2, p < .0001) had lower mean BMI. Those categorized as insufficiently active did not have significantly (p = .1748) different BMI from those categorized as inactive. Furthermore, the 4-level PA guidelines × sex interaction was significant (p = .030) and indicated lower mean BMI for females meeting either MSA only (b = -1.05 kg/m2, p = .0215), APA only (b = -1.14 kg/m2, p = .0014), or both APA and MSA (b = -1.84 kg/m2, p < .0001) guideline (p for trend < .0001). Whereas for males, only meeting both APA and MSA was associated with lower mean BMI (b = -0.77 kg/m2, p = .0077). Conclusion: This study found that meeting either APA or MSA guideline is associated with lower BMI in adults. However, sex-specific analyses indicate that this is true for females only and in dose-response fashion. Lower BMI in males is only associated with meeting both APA and MSA guidelines. Health promotion specialists concerned with obesity should understand the influence that each PA guideline has on relative body weight. Physical activity programming should promote both APA and MSA among adults in Montana.