Outside of the post-civilization period (which is trivial in duration in terms of timelines required for substantial evolutionary change given human reproduction patterns), I don't think sizable populations of humans have lived for significant periods of times in conditions where large volumes of food were available that didn't require substantial physical exertion to access.

"High food availability", sure, that occurred, but that only means a low risk of starvation with exertion to extract food from the environment. It is a very different thing than being able to avoid starvation while spending most of your time sedentary.

It's not just high food availability we have - I'm a few steps away from a ton of high calorie foods and could get more sent to my house without leaving my chair. In the past, even with plentiful supply, one had to [generally] put in some effort to get food. That doesn't seem to be the case for many now.

In the scenario of high food availbility meaning there's plenty of fruit to gather (and process to save for winter) and there's plenty of deer to chase then I can see I'd get more exercise.