This does not appear to be particularly surprising (?).

I think it is widely recognized that exercise and an active lifestyle can lower the risk of type 2 diabetes.

Remembering my cannabis consumption days, being under the influence of cannabis is not exactly a state that encourages an "active lifestyle".

Depends on your circles. Marijuana use is super prevalent amongst climbers (even while climbing, for better or worse) and it's a very active lifestyle. Same for surfers in my area. I don't think it's a given that people who smoke are less active.