sure but from google, he gained 25 pounds in a month. a pound of fat is about 3500 calories. 3500 calories/pound * 25 pounds / 30 days = 2916 calorie surplus. Morgan Spurlock is a 188cm tall man, which let's say he's 30 years old and 100kg (wikipedia says he gained 24.5 pounds/13% body mass), doing no to little exercise (he did walk 2km a day) that gives a Total Daily Energy Expenditure (TDEE) of 2406 calories per day (used this calculator : https://www.calculator.net/tdee-calculator.html?cage=25&csex...).
So basically, he had to be eating at the very bare minimum 5400 calories per day to get that much weight. To be fair, the wiki page says he did average 5k calories per day so he would have been lying only about 400 calories (minimum) per day.
Checking online, supersize me fried are ~600 calories and a big mac ~600. So let's say you eat that 3 times a day, that's 1200*3 = "only" 3600 calories. I find it hard to believe he drank 1800 calories worth of drinks per day to fill the gap, especially since he was allowed to drink water. Looking at canadian mcdonald's website, a large pepsi is 290 cals/77 grams of sugar, were supersize me really double that? If so, I guess the conclusion is don't drink 462g (literally over a pound) of sugar.
Your math is off because you're forgetting the beverage:
~600 kcal for a Big Mac
~600 kcal for Super Size fries (7 oz)
~500 kcal for a Super Size Coca Cola (42 oz)
1700 kcal/meal or ~5000 kcal/day if breakfast is the same as lunch and dinner
The calorie count for breakfast will likely vary. Note that orange juice contains more calories than Coca Cola per volume, but I don't remember a Super Size fountain orange juice existing.
Egg McMuffin and coffee for breakfast and then a Big Mac, medium fries and iced tea (or diet Coke or water) for both lunch and dinner is... 2130 calories. Not the pinnacle of the healthiest diet for sure. Over 30 days for a mid-sized dude, you might gain... one pound.
Absolutely, drinking diet coke or water is cutting out an enormous number of calories, as-is medium fries.
Heck, I only weight 185lbs and back when I ate mcDonald's a single Egg McMuffin wasn't nearly enough food to make me feel full. I'd get two and a hash brown, and still be hungry and hour later.
In the sister comment, I did some math and because the guy was 188cm and 220 pounds to start with, he needs 2400 calories per day just to keep his weight. He would have lost at least half a pound per week with the diet you just mentioned.
