Sitting on your desk for hours without taking a walk or stretch is harmful to your body, no matter what gender.
In Indian schools, teachers switch classrooms instead of kids during periods. Often they come early and stand at the door for the current teacher to finish and leave. This doesn't give any time to the students to stand up and cool off. There are also security cameras to punish students who start playing in the classroom between periods if the teacher is late.
Of course, some kids will still end up goofing around and sometimes take the punishment.
This ignores that there are kids with anxiety, disability and other problems which make them less likely to ignore the rules and risk getting punished.
This skews the data and people make incorrect assessment about the impact. There are many factors to consider here. I turn out fine is falling into that trap. You probably just goofed around and ignored the norms.
I wonder how much obesity rates in young people are influenced by the current schools.