Ever seen Walhlbergs daily routine? I can believe he keeps himself looking that way naturally.
Also remember we rarely see a lot of these people in their daily lives. Getting that absolutely chiseled look for a short period of time, in order to look great for a few scenes, is completely possible. It’s all about cutting a ton of water weight. It’s not really sustainable on a day to day basis. But to get in shape and look that way just on film naturally is totally possible.