In one scene, this nice doctor tells Spurlock he's been eating an average of 5,000 calories a day, even though he only Supersized 9 in 30 meals. At the end of the documentary, Spurlock had not only gained a bunch of weight and seen his cholesterol go through the roof (as you'd expect), but also had severe liver damage, as well as mood swings and depression.
Here's the thing: No one has been able to replicate Spurlock's results, and even basic math disputes the claim that his McDiet consisted of 5,000 calories a day.
As Tom Naughton points out in his documentary, Fat Head, there's simply no way Spurlock could have been eating that much food if he was sticking to his own rules. A large Big Mac meal clocks in at "just" 1,450 calories, and it's by far one of the fattiest items on the menu. This means that even Supersizing lunch and dinner every day and adding dessert falls well short of the 5,000 calories a day Spurlock's nutritionist claims he was consuming. In an effort to find out just exactly what the hell, Naughton attempted to contact Spurlock to obtain his food log, but Spurlock (who makes a huge deal in his documentary about McDonald's never calling him back) never called him back.
Meanwhile, researchers from the Making Sure Movies Aren't Stupid department of Sweden's University of Linkoping tried to replicate Spurlock's experiment by tasking healthy college students with the challenge of eating 6,000 calories of fast food per day, inadvertently also answering the question "What's the easiest way to get guinea pigs ever?" At the end of the 30 days, the students had none of the liver or cholesterol troubles Spurlock reported. According to the guy in charge of the experiment (aka an actual scientist, not the guy who created MTV's I Bet You Will), the students' metabolism was able to adapt to the extra amount of food they were eating. They did feel more tired, but none of them experienced the mood swings and depression Spurlock claimed to have endured.