Altitude Differences in Changes in Physical Activity and Weight Gain

Previous studies speculated that physical activity (PA) at high altitude represents greater actual exercise than when performed at lower altitude. Efforts are needed to validate or reject such speculation. This study explored the relationships between PA changes and weight/body mass index changes in low and high altitudes. According to a previous study and the altitude distribution of our participants, we classified the participants into low altitude (<2500 m) and high altitude (≥2500 m). The relationships between changes in PA and weight/body mass index were assessed through multivariable linear regression. Furthermore, the stratified analyses were conducted to detect whether there was heterogeneity in relationships between PA changes and weight/body mass index changes across low altitude and high altitude. A total of 10 000 individuals were included (9122 in low altitude, 878 in high altitude). PA increases, per MET-h/d, were inversely associated with weight changes in low altitude with a mean change of -0.009 kg (95% CI [-0.015, -0.002] kg), and in high altitude with a mean change of -0.032 kg (95% CI [-0.056, -0.009] kg). The inverse relationship between changes in PA and weight was significantly modified by altitude (<i>P</i> = .016), and it was stronger among participants residing at high altitude. It suggests that future guidelines and interventions should differentiate populations in low and high altitudes. Specifically, PA recommendations for people living at high altitude should be lower than those for people living at low altitude.