This section of the book is an abridged extract of an article written by John Cloud, 'The Myth About Exercise: Why Exercise Won't Make You Thin', Time Magazine, August 2009. Since 2009, further research has come to light confirming much of what is mentioned in the article that follows.
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Fundamentally, humans are not a species that evolved to dispose of many extra calories beyond what we need to live. Rats, among other species, have a far greater capacity to cope with excess calories than we do because they have more of a dark-colored tissue called brown fat. Brown fat helps produce a protein that switches off little cellular units called mitochondria, which are the cells' power plants: they help turn nutrients into energy.
When mitochondria are switched off, animals don't receive an energy boost. Instead, the animals literally become warmer. And as their temperature rises, calories burn effortlessly. Because rodents have a lot of brown fat, it's very difficult to make them obese, even when you force-feed them in labs. But humans — we're pathetic. We have so little brown fat that researchers didn't even report its existence in adults until 2009. That's one reason humans can gain weight so easily: we almost instantly store most of the calories we don't need as surplus body fat.
A study published in June 2009 in the journal Neurology found that older people who exercise at least once a week are 30% more likely to maintain cognitive function than those who exercise less. Another study, released by the University of Alberta in 2009 found that people with chronic back pain who exercise four days a week have 36% less disability than those who exercise only two or three days a week. But there's some confusion about whether it is exercise? Do these benefits come from sweaty, exhausting, hunger-producing bursts of activity or do such benefits come from regularly moving during our waking hours?
Could pushing people to exercise more actually be contributing to our obesity problem? In some respects, yes. Exercise depletes not just the body's muscles but the brain's self-control 'muscle' - we eat more when we get back from the gym.
Many obesity researchers now believe that very frequent, low-level physical activity — the kind humans did for tens of thousands of years before the leaf blower was invented — may actually work better for us than the occasional bouts of exercise you get as a gym rat. "You cannot sit still all day long and then have 30 minutes of exercise without producing stress on the muscles," says Hans-Rudolf Berthoud, a neurobiologist at LSU's Pennington Biomedical Research Center who has studied nutrition for 20 years. "The muscles will ache, and you may not want to move after. But to burn calories, the muscle movements don't have to be extreme. It would be better to distribute the movements throughout the day."
For his part, Berthoud rises at 5 a.m. to walk around his neighborhood several times. He also takes the stairs when possible. "Even if people can get out of their offices, out from in front of their computers, they go someplace like the mall and then take the elevator," he says. "This is the real problem, not that we don't go to the gym enough."
There's also growing evidence that when it comes to preventing certain diseases, losing weight may be more important than improving cardiovascular health. In June, Northwestern University researchers released the results of the longest observational study ever to investigate the relationship between aerobic fitness and the development of diabetes. The results? Being aerobically fit was far less important than having a normal body mass index in preventing the disease. And as we have seen, exercise often does little to help heavy people reach a normal weight.
So why does the belief persist that exercise leads to weight loss, given all the scientific evidence to the contrary? Interestingly, until the 1970s, few obesity researchers promoted exercise as critical for weight reduction. As recently as 1992, when a stout Bill Clinton became famous for his jogging and McDonald's habits, the American Journal of Clinical Nutrition published an article that began, "Recently, the interest in the potential of adding exercise to the treatment of obesity has increased." The article went on to note that incorporating exercise training into obesity treatment had led to 'inconsistent' results. "The increased energy expenditure obtained by training may be compensated by a decrease in non-training physical activities," the authors wrote.
Then how did the exercise-to-lose-weight mantra become so ingrained? Public-health officials have been reluctant to downplay exercise because those who are more physically active are, overall, healthier. Plus, it's hard even for experts to renounce the notion that exercise is essential for weight loss. For years, psychologist Kelly Brownell ran a lab at Yale that treated obese patients with the standard, drilled-into-your-head combination of more exercise and less food. "What we found was that the treatment of obesity was very frustrating," he says. Only about 5% of participants could keep the weight off, and although those 5% were more likely to exercise than those who got fat again, Brownell says if he were running the program today, "I would probably reorient toward food and away from exercise." In 2005, Brownell co-founded Yale's Rudd Center for Food Policy and Obesity, which focuses on food marketing and public policy — not on encouraging more exercise.
Some research has found that the obese already 'exercise' more than most of the rest of us. In May 2009, Dr. Arn Eliasson of the Walter Reed Army Medical Center reported the results of a small study that found that overweight people actually expend significantly more calories every day than people of normal weight — 3,064 vs. 2,080. He isn't the first researcher to reach this conclusion. As science writer Gary Taubes noted in his 2007 book 'Good Calories, Bad Calories: Fats, Carbs, and the Controversial Science of Diet and Health', "The obese tend to expend more energy than lean people of comparable height, sex, and bone structure, which means their metabolism is typically burning off more calories rather than less."
In short, it's what you eat, not how hard you try to work it off, that matters more in losing weight. You should exercise to improve your health, but be warned: fiery spurts of vigorous exercise could lead to weight gain. I love how exercise makes me feel, but tomorrow I might skip the VersaClimber — and skip the blueberry bar that is my usual post-exercise reward.
End of abridged Time Magazine Article
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