However you are right that it is chewier than commercial bread and I have also thought that this may be an additional explanation. I believe that the longer chewing time contributes to the satiation effect, but it cannot explain all of it, as I remain satiated for many hours, and I do not believe that the extra chewing can have a lasting effect.

In any case the fact that most modern food requires much less chewing than traditional food is indeed a likely contributory factor to the tendency of eating more at a meal than it was common for the previous generations.