You've listed the obesity rate, not the rate of people who are overweight. Beyond that, you haven't limited to adults. According to the CDC [1]:
Percent of adults aged 20 and over with obesity: 42.5% (2017-2018)
Percent of adults aged 20 and over with overweight, including obesity: 73.6% (2017-2018)
It absolutely has to do with lifestyle. America is one of the cultures most reliant on cars in the developed world. Physical activity is also ridiculously low. The problem is there's no way to reliably measure physical activity across countries. There's just survey data, and people in the US know they _should_ exercise.