Weight Loss: The New Myths
Behind the latest diet claims stand real doctors and reputable studies. Does that mean you should swallow everything they tell you? Not so fast.

By Barry Yeoman

Originally published in O, The Oprah Magazine, March 2006


TAKE THIS PILL. TRY THIS DIET. Buy this machine. Amid the steady stream of marketing hype designed to capitalize on our collective fear of fat, it's a rare thrill to hear about weight-loss news that's backed by actual science. A study published in a peer-reviewed medical journal? Great. Add a few PhDs or MDs after the researchers' names and perhaps the endorsement of a health foundation or university-even better.

But are studies always trustworthy? Is science necessarily pure? We investigated three recent weight-loss claims straight out of the lab and found the answers to be more complex than you might think.

The Finding: "Calcium helps make you skinny."

Behind the science: This most hotly debated diet claim is also the subject of a $120 million a year celebrity-studded marketing effort. "Milk your diet. Lose weight!" says an ad sponsored by the dairy industry, which suggests that drinking three cups of milk a day will help you flatten your stomach faster, as long as you also cut calories. Similar claims are made for yogurt and cheese.

The calcium-diet connection is based on a body of research-in particular, on several studies conducted over the past two years by Michael Zemel, PhD, director of the Nutrition Institute at the University of Tennessee, and published in respected places like the International Journal of Obesity and Obesity Research. In Zemel's experiments, obese dieters lost more weight, and also more stomach fat, when they significantly upped their dairy consumption.

The reason, Zemel explains, involves calcitriol, a hormone we have that some scientists think disrupts the burning of fat and stimulates the conversion of sugar into fat. In other words, the more calcitriol released, the more fully a Snickers bar will be turned into fat, and the harder it will be to exercise off the excess weight. Zemel also believes that the hormone interferes with the body's ability to kill off old fat cells. "The result of increased calcitriol levels, inevitably, is bigger, fatter fat cells and more of them," says Zemel. "That means bigger, fatter us." He theorizes that calcium, especially in combination with other dairy ingredients, helps suppress calcitriol's ill effects.

Zemel is quick to add that eating dairy won't help you lose weight unless you limit your overall food intake. "We don't have a magic bullet that can erase excess calories," he says. The even bigger caveat is that a calcium-rich diet helps only people who aren't getting enough of the mineral to begin with. Still, dairy producers jumped on Zemel's conclusions. "These findings could have a major impact on sales," read a memo distributed by the International Dairy Foods Association in 2004.

Critics, however, point out that Zemel's research, as the journals disclose, has been consistently underwritten by the dairy industry. They say this doesn't rule out good science but should be factored into his conclusions. Not only that, the calcium-weight loss claim based on Zemel's work is patented, and companies must pay licensing fees to use it on their dairy products. When they do, Zemel receives royalties. (The patent says his diet would also help peacocks, sea lions, wildebeests, giant pandas, and snakes slim down, although it hasn't been tested on these creatures.) Zemel insists his financial stake doesn't compromise his scientific integrity. Yet his results have not been replicated. In fact, they've been contradicted by other research-including some he's participated in-that shows dairy calcium having no effect on weight. In a recent Mayo Clinic study coauthored by Zemel and funded by the dairy industry, for example, 72 obese adults went on yearlong diets with about the same number of calories; those who consumed four dairy servings a day shed no more, or less, weight than those who consumed two. And when Susan Barr, PhD, professor of food, nutrition, and health at the University of British Columbia, analyzed 35 years' worth of research measuring calcium intake and weight change, "it was overwhelmingly convincing that there wasn't a major impact," says Barr, who is a member of the medical advisory board of the International Dairy Foods Association. "That doesn't mean there isn't a small subset of the population that's genetically distinct and would benefit. It just doesn't show up in the trials."

At this point, Barry Popkin, PhD, director of the Interdisciplinary Obesity Program at the University of North Carolina-Chapel Hill, says the studies linking dairy foods and weight loss are being pushed mainly by "folks with self-interest in the area." Because the available data is so contradictory, it makes sense to wait for further, non-industry-funded trials. Until then, milk and yogurt may be great sources of calcium, but loading up on them is not a proven way to lose weight.

The Finding: "Stress makes you fat."

Behind the science: Pamela Peeke, MD, hit the best-seller list with a book called Fight Fat After Forty, published in 2000, in which she laid out a research-backed association between chronic stress and weight gain. One of the culprits, she said, was the hormone cortisol. In the face of short-term stress, cortisol aids the body in mobilizing energy-helping a goalie intercept a soccer ball or a mother rush her child to the ER. Chronic stress, however, triggers too much cortisol, she argued, and that promotes abdominal fat storage, stimulates the appetite, and decreases muscle mass.

Most would agree that reducing stress is a healthy idea. What's dubious is the spate of diet products claiming to work by lowering cortisol, hoping to cash in on the new stress-diet connection. "Desperate housewives? Not so desperate anymore!" boasts an ad for one, featuring three trim women in sleek black dresses and high heels. The alleged secret to their physiques is the nutritional supplement CortiSlim. Earlier commercials, which the Federal Trade Commission cited in a false-advertising lawsuit, claimed the product was based on more than 15 years of scientific research while promising losses of up to 50 pounds. Shawn Talbott, PhD, the nutritionist who developed CortiSlim, settled the suit for $1.12 million. Meanwhile the pill's sales, reportedly, have gone on to surpass $200 million.

Talbott wrote a book called The Cortisol Connection that came out in 2002 and claims CortiSlim reduces cortisol through a blend of three ingredients: magnolia bark, the plant extract beta-sitosterol, and L-theanine, an amino acid found in green tea. He says the supplement is most effective when combined with exercise and a healthy diet. "Step off the scale and into the CortiSlim lifestyle-the start to a healthier, happier you!" promises the company's Web site.

Experts remain unconvinced that the product works at all. For one, they say the stress-cortisol-weight relationship is a loose one at best. "Not everyone who reports high stress is producing a lot of cortisol," says Elissa Epel, PhD, assistant professor in the department of psychiatry at the University of California, San Francisco. And while some investigations have linked excess cortisol with weight gain, the New England Research Institutes, which conduct trials for government agencies and commercial enterprises, recently found that obese men had significantly lower amounts of the hormone than normal-weight guys. "Despite popular claims that reducing cortisol levels could lead to weight loss, we find little evidence," wrote the study's authors.

That issue aside, doubts remain about whether CortiSlim even lowers cortisol. A thorough review of the medical literature on each of its ingredients found little to suggest that it would. "I don't think there is remotely sufficient support for the claim," says Stanford University neuroscientist Robert Sapolsky, PhD. "Certainly not support of a type that would satisfy the vast majority of metabolic endocrinologists."

Talbott has completed no clinical trials to bolster CortiSlim's weight loss claims. "He skipped that step and went straight to the dollars," says Wayne Askew, PhD, a University of Utah nutritionist and chair of the department for which Talbott taught a dietary supplements course. Talbott insists his product works. But he concedes that the trials are probably not forthcoming. "Studies are costly," he says. "They're time consuming. And there are some people in the industry who believe that you just don't need them."

The Finding: "Sleep more, weigh less."

Behind the science: If you want to diet successfully, go to bed. That's one message of the National Sleep Foundation (NSF), a nonprofit organization that receives about half its funding-$1.5 million a year-from pharmaceutical companies like Sanofi-aventis, which markets the sleeping pill Ambien, and Sepracor, maker of Lunesta. "Obesity has become an epidemic in this country, and so has sleep deprivation," declares CEO Richard Gelula, on the foundation's Web site. "We now believe that these two are linked more closely than we thought."

Given the sources of NSF's income, one might question its statement that sleeplessness is "the royal route to obesity." But in this case, the rhetoric is rooted in several good studies that are not funded by the foundation or pharmaceutical companies.

You don't need a PhD to see why, on four hours of sleep, one would be less likely to work out and more apt to reach for a box of doughnuts to get through the day than on eight hours of good rest. Now, however, scientists have more details about how sleep affects hunger.

"If you limit the amount of time you are in deep sleep, the brain interprets that as an insufficiency of energy stores," says Jana Klauer, MD, a research fellow at the New York Obesity Research Center of St. Luke's-Roosevelt Hospital. "It thinks you are in a state of starvation"-and ups your appetite accordingly.

In the past 15 months, two studies published in the journals Annals of Internal Medicine and PLoS Medicine have revealed the chemical mechanisms that throw a sleep-deprived person into a calorie-craving panic. When you don't get a full night's rest, the body's fat cells secrete up to 18 percent less of the hormone leptin, which signals to the brain that you have sufficient energy reserves and therefore don't need food. It's like the fuel gauge on your car: If your leptin levels are low, your brain wants to refill the body's tank. At the same time, the stomach produces too much ghrelin, a hormone that stimulates appetite. Among 1,024 volunteers, ghrelin levels rose 15 percent in those who slept five rather than eight hours a night. Not surprisingly, the shortest sleepers were also the chunkiest. "It really is the body-the stomach and the fat cells-saying, 'Eat more,'" comments Harvard sleep researcher Orfeu Buxton, PhD. "It's not just the mind."

Unfortunately, even with the best of science, no one has delivered a cure-all. Getting eight hours of sleep a night might make it easier to lose weight, but you still have to do the work by eating less and exercising more. And that's true for all diet breakthroughs at this point. "It's the food in and the calories out," Buxton says. "The rest stays around the middle."

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