The Frontal Cortex

The McDonald’s Diet

In the 2004 documentary Super Size Me, Morgan Spurlock decided to eat nothing but McDonald’s for 30 days. He ended up gaining lots of weight, suffering liver damage, and enduring intense mood swings. But now Spurlock’s movie has been repeated under experimental conditions. The results are good news for McDonald’s:

A Swedish researcher put 18 volunteers on the same diet that filmmaker Morgan Spurlock went on while filming “Super Size Me.”

To his great surprise, the researcher discovered that eating mass quantities of junk food affected each participant differently. While one volunteer gained 15 percent body weight after following the high-choleric diet for a month, several others experienced only minimal weight gain. [He] was thus forced to conclude that “some people are just more susceptible to obesity than others.”

The 12 men and six women were banned from exercising.

While all gained weight, none reported mood swings or liver damage like Spurlock did in the movie.

Update: Don’t rush out to McDonald’s for a quarter pounder yet. The story turns out to be a bit more complicated, as some of the subjects did have liver problems. See the astute comment below.


  1. #1 Lab Cat
    January 30, 2007

    I read this last night in New Scientist and as I know a subscription is needed to read the whole article, I quote a little extensively below.

    In this study the volunteers were able to eat all kinds of junk food not just McDs:

    “First Nyström calculated their normal daily calorie intake and then asked them to double it in the form of junk food, while also avoiding physical activity as much as possible. Nyström allowed them to do just 1 hour of upper body weight training per week. “I thought it would help some of the guys to stick to the diet if they believed that some of the extra weight could be in the form of muscle bulk,” he says. Aside from that, though, they were encouraged to be as slothful as possible, and were issued with bus passes and pedometers to help.

    In another difference from the movie, Nyström didn’t order his volunteers to eat only at McDonald’s. They were also allowed to eat pizza, fried chicken, chocolate and other high-fat food whenever they could no longer stomach burgers.

    So maybe there is something about eating McD that gives you mood swings.

    Also the conclusion about liver enzymes was a little different:

    “Either way elevated liver enzymes are a bad sign – and the main reason why Spurlock’s doctor urged him to quit his binge. Yet none of Nyström’s first batch of volunteers had this problem, which initially led him to suspect that Spurlock might have had an underlying susceptibility to liver dysfunction.

    Now that the Swedish experiment is complete, however, Nyström has revised this opinion. “The liver enzymes did increase a lot in some of the last study subjects,” he says. If he can find out what factors affect this variability, the supersize experiment may hold some vital clues for anyone hoping to understand and alleviate the growing problem of obesity-linked liver disease.”

    The final conclusion from the article seemed to be that everyone is different. Duh! Interestingly the two volunteers interviewed are now trying to lose the weight and gain back the muscle tone that they had before going on the diet as it did alter how they felt.

    Let me know if you want a copy of the NS article.

  2. #2 Dave Munger
    January 30, 2007

    I did the McDonald’s diet — for one day. I even made a website chronicling the experience. I cannot imagine how disgusting it would be to eat solely at McDonald’s for an entire month.

  3. #3 Kurt
    January 30, 2007

    Dave, of course you felt bad after one day of McDonald’s — you need to stick with it for at least a couple of weeks to let your body adjust to the new diet regimen!

    In all seriousness, I don’t want to defend McDonald’s, but I suspect that the fact that the subjects were instructed to double their caloric intake and cut back on exercise had something to do with the results. McDonald’s (and many other fast-food chains) rely too much on deep-frying as a cooking method (it’s fast, easy, and doesn’t require any training to do) and potatoes as a food source (likewise, plus they tend to be tasty). But knowing this, it’s not too hard to select a somewhat healthy menu from fast-food restaurants. I do have a problem with how McDonald’s markets its wares to kids, but they seem to be responding to public pressure and making some improvements in that regard.

  4. #4 quitter
    January 30, 2007

    After watching super-size me I was certain Spurlock has a susceptibility to NASH. His response to the higher cholesterol and fat diet was pretty extreme, I think he was just susceptible to the liver damage and the diet put him over.

  5. #5 jtdub
    January 30, 2007

    High-choleric diet, huh?

    I suppose it’s not much of a Freudian leap to equate McDonalds with fecal bacteria.

  6. #6 BenP
    January 30, 2007

    Wow, the ethical commitee agree on that ! Gross… 😛

  7. #7 fellowtraveler
    January 30, 2007

    Spurlock sort of touches on the individual differences in his film, he shows that guy who has been eating nothing but big macs for years and mentions his relatively low cholesterol level.

  8. #8 Jaimie
    February 1, 2007

    In my opinion I dont think that it would be possible to loose weight from eating mcdonalds. The food is gross, and extremely greasy, and I dont care what anyone says it is not good nor is it healthy.

  9. #9 Peter Lund
    February 4, 2007

    The amount of trans fatty acids in McD food varies a lot between countries. There is a Danish researcher who collects fast food from all over the world and measures its trans fatty acid contents.

    The US fast food is terribly bad (but not the worst kind!) and the Danish fast food is practically free from it — as it is required to by law.

    As far as I recall his results, Sweden has a low trans fatty acid contents in its burgers and fries (but not as low as DK).

    Wouldn’t such a difference explain a lot?

  10. #10 Jen
    October 29, 2010

    It is so hard to use Maccas when you are not used to it, tastes and looks so artificial, unlike in pictures.

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