What made people so fat?

I read somewhere that there were way fewer obese people in sedentary office jobs 50-80 years ago than they are nowadays. I could not imagine that diets changed so drastically that people have such a high caloric intake nowadays (speaking from a European perspective). I also feel like sports are more popular than ever before, especially weightlifting/bodybuilding and combat sports, which surely take a lot of energy and also shape the body.