Introduction:
Smartphone addiction (SA) is a growing problem among adolescents, and it may have adverse health outcomes. The aim of this study was to analyse the risk of SA according to the level of physical activity (PA), and the occurrence of overweight and obesity in a population of 460 adolescents – students of secondary schools in Poland.

Material and methods:
The physical activity of adolescents was assessed using a short version of the International physical activity questionnaire. Smartphone addiction, as the independent variable, was measured by the mobile phone addiction assessment questionnaire. Overweight and obesity were identified by body mass index (BMI). Waist-to-hip ratio and body height were also measured.

Results:
284 (61.7%) respondents were not addicted to the smartphone, 148 (32.2%) were at risk of addiction, and 28 (6.1%) were addicted. It was found that in all respondents (n = 460) SA was associated with PA – low overall PA was associated with a higher level of SA (rho = –0.279; p < 0.0001). Moreover, the index of overall SA increased with sitting time (β = 0.113) and decreased with the general PA growth (β = –0.190). It was also shown that the increase of SA in overweight/obese adolescents was influenced by the reduction of general PA (rho = –0.343; p < 0.05), intense PA (rho = –0.268; p < 0.05), and walking (rho = –0.280; p < 0.05). Smartphone addicts were also students with higher BMI (24.77 kg/m2; p < 0.0001) and higher BMI percentile (80.57; p < 0.0001).

Conclusions:
Smartphone addiction is significantly associated with the PA of adolescents, and it is more common among those with an insufficient level of PA. Increased BMI is also an indicator of SA. Interventions for reducing SA should take into account both the context of PA and anthropometric indicators of schoolchildren.