By the end of Spurlock's McDonald's binge, the film-maker was a depressed lardball with sagging libido and soaring cholesterol. He had gained 11.1 kilograms, a 13 per cent increase in his body weight, and was on his way to serious liver damage. In contrast, Karimi had no medical problems. In fact, his cholesterol was lower after a month on the fast food than it had been before he started, and while he had gained 4.6 kilos, half of that was muscle.In the end, the results--at least to this lean, always-hungry food fiend--should surprise no one. Different food affects different people differently. You need to tailor your eating to your own needs, not to a government-mandated pyramid or to a restaurant's massive serving suggestions.
The brains behind this particular experiment is Fredrik Nyström from Linköping University in Sweden. In the past year he has put 18 volunteers through his supersize regime, and what fascinates him most is the discovery that there was such huge variation in their response to the diet. Some, like Karimi, took it in their stride. Others suffered almost as much as Spurlock, with one volunteer taking barely two weeks to reach the maximum 15 per cent weight gain allowed by the ethics committee that had approved the study. We are used to being told that if we are overweight the problem is simply too much food and too little exercise, but Nyström has been forced to conclude that it isn't so straightforward. "Some people are just more susceptible to obesity than others," he says....
The first batch of seven healthy, lean volunteers began their month-long challenge in February 2006. 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.
During the experiment Nyström's volunteers had weekly safety check-ups to monitor their health. In addition, they were subjected to a barrage of tests and examinations before starting the diet and again afterwards to find out what it had done to their physiology, metabolism and mental health. "We've done almost every test apart from a muscle biopsy," Nyström says.
His team used a state-of-the-art X-ray technique called DEXA (dual energy X-ray absorptiometry) to measure body composition, including muscle, fat and bone density. They subjected the volunteers to glucose tolerance tests to look for early indicators of metabolic syndrome and diabetes, plus a new spectroscopy test to assess the amount of fat in the liver. They measured their basal metabolic rates before, after and during the experiment, using a standard measure of how much oxygen they inhaled and carbon dioxide they exhaled over a period at rest. They took blood samples and measured levels of hormones such as thyroxine that play a role in setting metabolic rate. And in a bid to work out exactly what metabolic changes occur in fat cells during a fatty diet, the researchers even screened mRNA, the molecule that acts as an intermediate between genes and the proteins they code for. "We looked at all proteins - that's around 30,000," says Nyström.
Today's lunch: pizza, Pepsi, and a couple Nanaimo bars. Some of us just have all the metabolic luck.