There are two polarised reactions to Morgan Spurlock's 2004 documentary Super Size Me, in which the American film-maker ate nothing but McDonald's food for a month. Lots of people are disgusted to see what happens to the 33-year-old's body as he accepts Super Size shake after Super Size shake and limits himself to 5,000 steps a day and are shocked as his liver becomes toxic, his cholesterol skyrockets and his libido sags. Everyone else thinks: hey, how bad can it be? I wouldn't mind doing that.
Well, at one Swedish university, a group of students are getting the chance. At the University of Linköping, the Spurlock experience is being replicated under clinical conditions. In February, seven healthy medical students in their early 20s spent weeks stuffing themselves with hamburgers, pizzas, milk shakes and 200g bacon breakfasts - all on the university's tab. A second group of subjects are just now hitting the junk food. Physical exercise is to be avoided. Bikes are out. To discourage walking even the shortest distance, free bus passes have been issued.
The study is the brainchild of Fredrik Nyström, doctor and associate professor at the university's department of internal medicine. Finding himself with a little extra money in his research budget last year, he decided to do something "fun, something lasting". And ever since watching Super Size Me he had been thinking of how, in all the studies of obesity and metabolism, hardly anyone has studied what happens when you force healthy people to put on weight. The few studies there have been took place in the 60s and 70s.
The reason, speculates Nyström, is because it is difficult to ask people to get fat in the name of science. "It's far easier to study those who are fat to begin with," he says. "They're appreciative and keen, happy that someone will help them slim. And in the US, I assume this kind of study would be out of the question. Everyone would get sued if the subjects afterwards didn't manage to get rid of their extra kilos." But in laidback Sweden, there were no problems clearing the experiment with the national ethical board. The one proviso Nyström added was that he would pull anyone out of the experiment if they increased their bodyweight by more than 15% - even if he or she was prepared to go on.
It wasn't difficult for Nyström to find willing guinea pigs. Late last year, after delivering a lecture on the ills of overeating, he casually asked if any of the students would be prepared to gorge themselves for the sake of science. He was deluged with applications, but mostly from men (he thinks that women are too wary of gaining weight). They all had to be in good health, but as he says: "Young med students usually are." Nyström then simply chose the ones who seemed "the most highly motivated". At the end of the month, each student was they were given their results to keep.
Before the study began, the subjects thought they were in for an easy time. In fact, they could hardly believe their luck: "You mean to tell me that if I were to go out tonight, and order beer and peanuts, you'd pay?" said one incredulous student. But eating 6,000 calories a day - roughly double what most of the volunteers ingested normally - is not as easy as it sounds. You can't do it simply by letting yourself go and having an extra scoop of ice cream. It takes effort. One Big Mac with large fries and a large Coke still nets you just 1,164 calories, according to McDonald's Swedish website.
Just as in Super Size Me, the idea was that all calories would come from fast food. But breakfast at home was allowed, provided it was bacon-and-eggs based. And the fast food didn't have to come exclusively from McDonald's: hamburgers could be exchanged for pizzas, as long as most of the calories still came from saturated fats, those having the most effect on levels of cholesterol. Still, it wasn't unusual for students to be about to go to bed only to discover that they were some 600 calories short of their daily target, and forced to face a large calorific milk shake rather than a mug of hot milk.
It turns out that hunger might be an underrated feeling. Towards the end of the study, most of the students stated that they were looking forward to being ravenous again. Going for a month feeling continually sated felt odd. And though few of them were fitness freaks, most hated not being allowed to walk or cycle around. Nyström was surprised to find "there was more whining about that than about the eating".
The students managed to gain between 5-15% extra weight over the month. They felt "tired and bloated", especially during the first week, but there seemed to be no signs of the mood swings towards the end that the rather despondent Spurlock reported.
Final results from the questionnaires will be released at the end of the study. But judging from the provisional results, no one suffered anything like as much as Spurlock. One of the most shocking scenes in the film is when his three doctors urge him to abandon his experiment after getting the results of blood tests which show that his liver is so badly damaged it looks as though it is the result of heavy drinking - "You're pickling your liver!". While Nyström and his team also noted "significant" changes in the liver, relating to the liver enzyme levels in the blood, and the content of fat in the liver, the changes were "never even close to dangerous".
Nyström is puzzled about why Spurlock had such an extreme reaction, musing that he could perhaps have had an undiagnosed problem with his liver or, he says, "Maybe his hardcore vegetarian girlfriend held him to a low-energy diet, making him incapable of coping with this kind of food."
Interestingly, in the Swedish experiment, while the liver readings got steadily worse until the third week, they then took a turn for the better. The liver, it would seem, adapts. Cholesterol, meanwhile, was hardly affected.
And this is the most fascinating thing: if Nyström's small group are representative, then it would seem that our bodies are more adaptable than we give them credit for. In other words, metabolism may play a much more important role in the problem of obesity than many people think. Indeed, Nyström claims that for some people, eating 10% more will lead to their metabolism increasing at the same level. The extra energy will be burned off as body heat during sleep. "If that was not the case we would all have to keep track of every last calorie," he says. "And you have to realise that some overeaters consume such grotesque amounts that they would be even heavier - much heavier! - were it not for this safety mechanism."
That's why these kind of studies have to be carried out, he says: "If you only look at the already overweight, you'll only do research on those with least resistance to calories, so to speak."
The first part of the study finished in June; the next batch of subjects are now stuffing themselves with Big Macs. Nyström expects to publish final results after Christmas: not a bad time of year to publish a report blaming individual metabolism for weight gain.
