Impact of Fitness Influencers on the Level of Physical Activity Performed by Instagram Users in the United States of America: Analytical Cross-Sectional Study

Background: Physical activity positively influences the general population’s health. Social media networks may promote changes in physical activity habits. This study aimed to analyze the relation between being encouraged to perform physical activity by fitness influencers on Instagram and the level of physical activity performed. Methods: An analytical cross-sectional study was performed in 890 United States residents with an Instagram account. The sample was made up of 79.2% females and of 75.4% millennials (born between 1981–1996). Physical activity was measured with the International Physical Activity Questionnaire. Sociodemographic characteristics were registered. Results: The percentage of females (p = 0.001), millennials (p < 0.001), students (p < 0.001), participants with normal BMI (p = 0.001), and participants performing more than 150 min per week of moderate physical activity (p = 0.014) was significantly higher in the group that felt encouraged to perform physical activity by the information posted by fitness influencers. This group spent a median of 2 h per week on Instagram checking for nutrition or exercise (p < 0.001). Conclusions: United States residents who felt encouraged to perform physical activity by fitness influencers on Instagram achieved more the World Health Organization recommendations for substantial health benefit for moderate physical activity. They were predominantly females and millennials with normal weight and spent more time on Instagram checking for nutrition or exercise.