peoples idea of what it is to be active or sedentary has been misaligned by a society built on making things physically easier, essentially because we’ve evolved to do so (conserving energy is something we once had to do to survive).
This way of life is now so normalised we don’t even consider it in these discussions.
Therefore surveys are of little value. The once or twice a week gym go’er will consider themselves active, fit even. But in actual terms can still be sedentary; they’ll spend 14 hours a day sat on their backside in the car, in the office or at home.
I work from home. I’m a 15 stone, 5′ 8″ male, on the bmi scale I’m obese. To just prevent weight gain I eat 1500 calories a day (except on Saturdays), walk the dog and do 10 mins of callisthenics twice a day, and run 2-3 miles on Tuesdays, Thursdays, and Sundays. I’m neither gaining or losing at that activity level, why? Because pretty much the rest of the time I’m sat in front of a computer or in bed.
In my opinion the shift required to arrest the growing number of obese people is unrealistic without a much more fundamental look, and ultimately change, in the way we live, work, and think.