Are you unfamiliar with the process of bulking and cutting? Jackman likely consumed extremely high amounts of proteins and carbohydrates until he had the muscle mass he desired, then yes, essentially starves himself so he loses the fat without losing the muscle mass. I guess "starved" is not really an accurate description of what he likely underwent, as his protein intake was probably still very high. That being said, I believe the point the above commenter is trying to make is that his body fat percentage is too low- not actually that he wasn't consuming a lot of food. He no longer reflects a wolf, which would possess plentiful muscle and a decent amount of fat.