Its both. In developed countries kids are playing Fortnite, watching streamers on Twitch etc. and pinging their friends on social media vs. every decade up until the early 2000s, where kids essentially went outside all day anytime they weren’t in school. In the US, dozens of dietary factors are also to blame. Subsidized corn, poor nutrition education, ubiquity of fast food and fast casual restaurants, snack food marketing around social events like holidays and the Super Bowl, advent of food delivery apps, growth of the “body positivity” movement etc. are all reasons people have trended toward obesity.