The Science of Yoga

relaxation. The men and women—their average age thirty-three—followed the prescribed routine for at least a half year.
    The scientists assessed how the routine affected the basal metabolic rate—the energy spent on the body’s housekeeping functions. In a standard method, they measured the flow of respiratory gases—oxygen and carbon dioxide—as a way of gauging how bright the inner fires were burning, as measured in calories.
    In 2006, Chaya and her team reported that regular yoga practice cut the basal metabolic rate by an average of 13 percent. The results were even more pronounced when broken down by sex. The men on average cut their resting energy by 8 percent. But the women achieved reductions of 18 percent—more than double the metabolic declines of their male counterparts.
    It bespoke the wisdom of Robin’s comments about autonomic cycles. The ups and downs worked to increase not only outer flexibility but inner suppleness as well, giving body and mind the freedom to sink into Benson’s kind of quietude—to just be. It was a secret of letting go.
    The metabolic dips also raised an issue that bore on personal appearance rather than moods but was too central for the scientists to ignore. Chaya’s team noted that physiological slowingof yoga in theory “creates a propensity for weight gain and fat deposition.” In other words, individuals who took up the discipline would reduce their basal metabolic rate to such an extent that they required less food and fewer calories—or would add pounds if they ate and exercised in the customary manner.
    This novel finding of physiology might have won attention, but it clashed with the happy talk of popular yoga. Teachers, the Internet, and how-to books had long echoed with confident declarations that yoga speeds up the metabolism and results in an almost magical loss of weight. It was one of modern yoga’s credos— equal in some respects to the illusory surge of oxygen to the body and brain. In truth, the metabolic conviction was so deeply held that no inconspicuous finding in faraway India stood a chance of undoing the fashionable myth.
    Tara Stiles exemplified the durability. The attractive model turned yoga teacher favored short shorts and tank tops, and managed to keep herself beanpole thin. In Manhattan, she ran Strala Yoga in NoHo, a chic neighborhood north of Houston Street. In 2010, she came out with Slim Calm Sexy Yoga , its cover emblazoned with a photograph of Stiles in an eye-catching pose. The book featured an endorsement from Jane Fonda and rose fast to become the number-one yoga seller on Amazon. Early in 2011, The New York Times profiled Stiles, saying the twenty-nine-year-old displayed not only sexy good looks but down-to-earth charm.
    The title of her book led with Slim , and Stiles worked hard in the text to deliver on the promise. She devoted a chapter to slenderizing and explained what seemed to be the scientific basis for why the discipline worked so well at keeping off the pounds. Yoga, she declared, will “rev up your metabolism.” Getting specific, she recommended a series of postures meant to throw the body into high gear in the service of shedding weight. “Even if you think you have a sluggish metabolism,” Stiles said, “practicing this routine twice a week will keep it humming—and help you burn calories all day.” She emphasized the point in large type spread across the top of the page, advertising her custom routine as “Metabolism Revving.”
    The bold declarations of Stiles not only contradicted the body slowdowns that the Bangalore team had documented. They also clashed with the particulars that Mel Robin had told our class. For instance, Stiles listed the Shoulder Stand as one of her metabolism lifters. In contrast, Robin had described theinversion as “one of the most relaxing postures in yoga.” And Gune, of course, had recommended the pose to Gandhi for its calming action.
    Chaya, the physiologist in Bangalore who had practiced yoga since childhood, told me that the secret of weight loss had nothing to do with a fast metabolism and everything to do with the psychological repercussions of undoing stress. “Yoga affects the mind—and desire,” she said. “So you eat less.”
    If yoga can foster serenity and lift moods, what are its repercussions for depression, where the requirements for emotional uplift are much greater? It was a tough question. Amy Weintraub in her book, Yoga for Depression , recounted