When I was in my late teens to late 20's I could and often did eat at least as much as the fellow in the movie, usually not calorie-wise but certainly volume-wise. This included some short spells of lots of fast food within whatever usual routine of omnivorous or vegetarian fare. At the time, I weighed from 125 to 130 lbs. (57-59 kg), max. I never threw up because most of the time the food was anywhere from half-decent to pretty good. At thanksgiving I could eat two very full plates and then a third 'normal' plate.
But even with such capacity as I possessed at the time, had I attempted three meals per day on a fast food menu, I'm sure that even I would have tossed the meal on occasion. So then, the amount eaten certainly was a factor in the filmmaker's bodily rejection of the food, but I assure you the 'quality' of the food, such as it was, was at least as great the reason for the rejection. Additionally, had he eaten the same volume of rice, beans, and stir fry vegetables, either with out or with (good) meat in it, he would not have had any liver problems.
As to the overwrought nature of the escapade (and I certainly agree with others' assessment of that), well, that's just part and parcel of today's media, especially rhetorical theatre, where presenters feel the need to shout as loudly as possible, exaggerate, contort, be in our face, hammer us over the head, and impale upon us whatever point they feel it so important that the audience get. I don't understand this approach at all as a way to try to convince anybody of anything, but then I don't 'get' about 98% of anything in today's films or the media or on the television anyway, so just add it to the list.
BTW, when I stayed at the completely vegetarian regime for over 12 years, I got myself up to a whopping 155 lbs. (from the prior ~128) and been there or near it ever since, though I now sometimes eat meat that friends cook when invited to dinner.
I suspect the difference there was that before, I just ate 'whatever,' didn't cook very well, so not that often, sometimes just as happy having half a leftover ham sandwich followed by two or three large bowls of some cold cereal w/ milk, and two large pieces of toast with about a quarter stick of butter between the both of them for the evening meal. If I was still hungry, I might make a large cheese sandwich or open up and heat a store-bought can of chili (yuk, I know). Choice, huh? But the more vegetarian I ate, the better I got at cooking, to the point where my girlfriends preferred that I do most of the cooking. Anyway, just eating better food, which for me meant something that I or another person made in the kitchen (because I learned how to cook well), got my body to the weight it should have been and I had noticeably more energy. And nearly identical diet regime has gotten acquaintances who were somewhat overweight (including one of aforementioned girlfriends) down to a weight more natural to them.
I think that the greatest benefit of cooking aside from it being fresher is that you pay more attention to the ingredients, being that you look at and handle them, thereby somewhat automatically improving the quality of those ingredients. Less additives, food coloring, 'stabilizers,' etc. That useful adage, "what's good for shelf life is usually not good for human life" is often to mind here.
It can be a bit tedious chopping vegetables, but I make enough salad for two meal sized servings, tabouli ( I put tom-ay-to in the tabouli, but to-mah-to in the tabbouleh ) enough for 3 days, the bean or veggie casseroles for 3 days, brown rice always in the fridge, etc. Between that and the bananas, pears, broccoli to shovel hommus with, et. al., I can go three days with just a couple of re-heats being the only actual cooking. If making one chicken breast, you can make two, dice some to put in a stir fry or casserole later.
The more experience you get, the more ways you find how to reduce average cooking time per meal, and the leftovers are still twice as fresh as what you could get elsewhere.