It was impressive to see how sickly he started to look, though in fairness the director did show one guy who's eaten a surprisingly large number of big macs and still looks reasonably trim. (Though apparently he only eats big macs, he doesn't do the fries.)
However after seeing that movie I think I need more exercise.
Several of his doctors were completely horrified at how badly his liver was responding to the all MacDonald's diet. He started in perfect health and by about day 21 they were warning that if he felt a pain in his jaw or along his left arm to immediately go to the emergency room. They were quite surprised that a "high fat diet" was as bad as binge drinking.
Also his vegan chef girlfriend managed to get him to go on a "detox" diet of her devising, and his cholesterol dropped quite quickly. (Of course he only kept that up for 6 weeks).