Very good question. I've found finding specific data that you can compare over time, particularly across different nations hard to come by. This kind of data just wasn't tracked reliably until recently.
Yep. Anything interesting and slightly different from standard is hard to do. My a level course work was all about the barriers girls face in being active. I picked the topic because The allied dunbar study of the time reported that girls were far less active than boys and that's exactly what I saw in my school. Being the same age I thought I could understand why. Simple things like appearance can get in the way. Believe it or not some girls didn't want to be seen sweating. They felt it would make them look ugly. Given the pressures at that age or any age and what I see in the wider media it doesn't surprise me.
Guys face the same pressure but from a different angle. Then when we grow up it's just really hard to fit activity around a day job, kids and other commitments. Especially since most people socialise sitting or standing and with a ton of food and drink around.
You've helped me give more context to the activities in this course. Essentially food, nutrition and many other aspects are well researched areas. Always have been. Activity is not. The benefits are generally misunderstood and/or ignored.
The role of activity in losing weight for example has for years been negated because the direct amount of calories burnt from even intense activity is very little compared to cutting down on food. On the face of it this is true but it's too reductionist. There are studies showing that bones are stronger in active people than inactive despite both taking calcium supplements thus exercise directly protects against osteoporisis. That sugar regulation is better in active people than non active so it can protect against type 2 diabetes. This can be explained right down to the cellular level in that cells get better at listening to insulin through activity. It's a training effect that has been monitored in the lab.
This is the kind of information I want to bring out over time and I want to see what everyone else has to share aswell. Thanks for bringing this out.
You can imagine I can go on but I'll stop my rant there :-).