After hearing the sad news that non-smoker Dana Reeve has died of lung cancer, I was reading about Christopher Reeve on wikipedia. Even though he had "stunning good looks and a tall stature at 6'4"," his build was "decidedly unmuscular" for the role of Superman and he was put on a training regimen under former British weightlifting champion Dave Prowse:

Reeve had a driver who was paid to take him to the gym no matter how much he cursed and resisted. The training regimen consisted of several hours at the gym every day, and eating two of everything; two breakfasts, two lunches, and two dinners. Reeve put on 30 pounds of muscle to his thin 180 lbs frame, and put on even more for Superman III. Once he reached the peak of his bulk, he decided to put more emphasis on cardiovascular workouts and became leaner.