I remember a few years ago he was on the cover of Mens Health (surprise surprise!) and I read the interview he gave. He said that he rarely (if at all) performs the same workout twice, he loves to mix up his workouts - he's not just in the gym all the time (not that often at all actually). He's studied Wing Chun, Kung Fu, Karate and Kick Boxing. He is known for doing his own stunts - which is very rare in movies these days. He incorporates those four disciplines into his workouts - he's incredibly fit, athletic and flexible, and this shows in movies such as The Transporter.
In most of his movies he is portrayed as a 'tough guy', and that's not a surprise, as he kind of is in real life! The training he puts himself through is crazy. To get in (and to keep in) shape at his age is very hard indeed, but he manages to do it. Lifting weights in a gym can be hard, but to train in four disciplines of martial arts, as well as more traditional workouts, that's tough. Why doesn't he just hit the gym and weights for every movie instead? Easy answer - he enjoys how he trains. In the interview he said in the past he has gotten bored with just lifting weights, and wanted to do other things in order to get in shape for his movies. I don't think anyone is in the position to say what he does is wrong - it clearly works for him.
Is he a 'tank'? no, but that's for a reason. In order to do some of the movies that he has done, if he was 'massive', he wouldn't be able to do the fight scenes, he simply wouldn't be fit or flexible enough. You'll never see an amazing fighter who is the size of a bodybuilder, because you can't move fast enough. I don't know if 100% of his fight scenes are all him, but from what I've read he has pretty much done them all himself - which shows great skill. If he didn't turn to those four disciplines, he might not have had the success that he's had.
All in all, Jason Statham is one of the very best action actors out there, and his fitness plays a huge part in that. He is an example of 'you're never too old to be in shape'. Yes he has a lot of money so he can afford the best diet, but some of his training is very 'old school', which is not a lot of money at all. Just remember, the gym is a great tool to get in shape, but it's not the only way.
Lee Gregory Fitness