15. Chris Hemsworth
Audiences know him by one name: Thor. Hemsworth had a career before the Marvel movies, but it was Thor that put him on the map. For that, the young surfer had to put down his board and pick up a few dumbbells to gain 20 pounds. Then, when he landed the role of Owen Chase in the movie In the Heart of the Sea, he lost 33 pounds from his standing weight. Some days he lived on an egg, some crackers, and a celery stick to lose the weight.