The Science of Yoga: The Risks and the Rewards (19 page)

Robin expanded the activity explanation a step further and showed us subtle ways in which a pose could engage the parasympathetic brake. His ideas were an elaboration on what he had told me during the inversions class.

He focused on the heart itself. Robin noted that the right atrium—the upper chamber that gets blood from the veins—bears a sensor that gauges its fullness. When
pressure is low, he said, the sensor signals the heart to beat faster, increasing the blood flow. When pressure is high, the heart slows down.

Robin said inversions worked beautifully—as with carotid pressure—to fool the heart into slowing. It happened because upending the body dramatically increased the flow to the right atrium. Normally, gravity helped a little between the head and the heart. But turning the body upside down let gravity work over a much larger area, strengthening venous flow from the feet, legs, and torso.

“It’s all downhill,” Robin noted. “So the heart overfills.”

The rising pressure in the right atrium then signaled the heart to beat slower. That signal, Robin noted, also caused the heart to reduce the strength of its contractions. It was a one-two punch. Overall, the atrial mechanism showed yet another way in which yoga could work inconspicuously to reset the metabolism.

Robin had us do a heart test. First, we monitored our pulses, measuring their rate against the sweep of a watch. Then he had us move to a wall, lie on our backs, and raise our legs in a relaxed state of partial inversion. Once again, we measured. He noted that the beat was probably slower (which I found to be the case).

A good yoga practice, Robin said toward the end of class, involved poses that cycled through the accelerator and the brake so the autonomic system got a thorough workout. Robin said the resulting realization of energetic flexibility over the usual conditions of metabolic life resulted in new abilities to achieve states of inner balance and harmony.

“A large part of the benefits,” he said, “results from going through a couple of cycles every time we practice.”

The clues gathered over the decades about yoga’s repercussions for human emotion first began to come together in a significant way at Harvard. Herbert Benson was a physician eager to ease Western tension with regular doses of Eastern calming. He and his colleagues studied the issue at the university’s medical school, examining the effects of meditation, yoga, and other soothing practices. Benson called his insight
The Relaxation Response.
His book, published in 1975, sold more than four million copies and became a modern classic on undoing stress.

Benson found that simple techniques could have dramatic repercus- sions on his subjects,
cutting their heart rate, respiratory rate, oxygen consumption, and blood pressure (if elevated to begin with). Overall, he and his colleagues showed that relaxed practitioners entered a state known as hypometabolism—a wakeful cousin of sleep that exhibits low energy expenditures. He called the relaxation response “an inducible physiologic state of quietude” that healed and revitalized.

After Benson, many scientists sought to expand his findings and zero in on particular disciplines, including yoga.

Mayasandra S. Chaya was an Indian physiologist in Bangalore who had practiced yoga since she was ten. Chaya led a team that studied more than one hundred men and women. The scientists prescribed a diverse Hatha routine sure to press both the metabolic brake and accelerator. The dozen poses included the Triangle (Trikonasana), the Shoulder Stand (Sarvangasana), the Locust (Shalabhasana), the Cobra (Bhujangasana), the Bow (Dhanurasana), and the Thunderbolt (Vajrasana), as well as fast and slow breathing techniques. At a session’s end, the subjects assumed the Corpse (Savasana) for a period of conscious 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 slowing
of 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 the
inversion 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 her own experiences and prescribed many practical ways of dealing with the blues. But depression has many faces and, in its most severe forms, is crippling.

Everyday gloom involves low feelings and loss of pleasure, perhaps due to minor setbacks. That kind of dejection, by nature, is fleeting. By contrast, the symptoms of clinical depression last two weeks or more. A seriously depressed person can feel anything from hopelessness and discouragement to worthlessness and despair. The World Health Organization says that, every year, nearly one million despairing people take their own lives. That is more than the number of people killed annually in crimes or war. In industrialized societies, despite floods of antidepressants, rates of suicide and depression are going up, not down.

Once again, scientists in Boston zeroed in on the question. Their studies went far beyond clinical trials and patient evaluations to examine neurochemistry. The team represented the elite of the Boston medical world—the Boston University School of Medicine and the Harvard Medical School and its McLean psychiatric hospital. The hospital is famous for its neuroscience research as well as its extensive roster of celebrity patients, including the mathematician John Nash, the poet Sylvia Plath, and the musician James Taylor.

Chris C. Streeter, the head of the team, held faculty appointments in psychiatry and neurology at the Boston University School of Medicine and lectured in psychiatry at the Harvard Medical School. Plus, she knew yoga and knew people who knew yoga. Her team focused on an important chemical in the human brain that goes by the tongue-twisting name of gamma-aminobutyric acid
—or, easier to say, GABA. It is a major neurotransmitter and regulator of the human nervous system. Many reports have linked depression to low GABA levels. So a smart question was whether yoga went about easing depression by raising concentrations of the neurotransmitter.

Scientists have known about GABA since the 1950s. But it took a long time to understand its role in the brain and to develop the scientific tools to easily track its comings and goings. GABA works by blocking actions rather than causing them. It is known as an antagonist. Such chemicals, when they bind to cellular receptor sites in the nervous system, disrupt interactions and inhibit the functions of other neurotransmitters. In general, GABA slows the firing of neurons, making them less excitable. So high levels of the neurotransmitter have a calming effect. When alcohol and drugs like Valium bind to GABA receptor sites, they increase the molecule’s efficiency and thus promote its actions as a sedative and a muscle relaxant. GABA itself tends to promote relaxation and reduce anxiety.

By the 2000s, brain imaging had advanced to the point that tracking GABA could be done fairly inexpensively. Scientists judged the time right to address the yoga question.

The team found lots of potential subjects. Boston, starting with Thoreau and James, had evolved into a yoga hotspot. In modern times, it pulsed with many thousands of practitioners.

The team selected eight who practiced a number of diverse styles. They were Ashtanga (the gymnastic style developed by Pattabhi Jois, a student of Krishnamacharya’s), Bikram (the hot yoga of Choudhury), Hatha (the ancient classic), Iyengar (the modern classic), Kripalu (developed by the Berkshires center), Kundalini (the heavy-breathing style popularized by Yogi Bhajan, a Sikh mystic), Power (an aggressive form of Ashtanga), and Vinyasa (a flowing style developed relatively late in life by Krishnamacharya and popularized by his student Srivatsa Ramaswami). The subjects had practiced yoga anywhere from two to ten years. They were all white, mostly female, mostly single, and averaged twenty-six years in age. Prior to the study, all had practiced yoga at least twice a week.

The team measured GABA levels before and after an hour-long yoga session. The routine was standardized to focus on asanas and related breathing. At the start
and end, the students could engage in brief sessions of quiet contemplation. But they were allowed no extensive periods of meditation or pranayama. The study guidelines called for at least fifty-five minutes of common asanas, such as inversions and backbends, twists and Sun Salutations. To ensure a degree of standardization, a research staff member with yoga training observed the sessions. The scientists compared the eight yoga practitioners to a control group of eleven individuals who did no yoga but instead read magazines and popular fiction for an hour.

The results, published in 2007, fairly glowed. The scientists found that the brains of yoga practitioners showed an average GABA rise of 27 percent. By contrast, the comparison group experienced no change whatsoever. Moreover, the yoga practitioners with the most experience or who practiced the most during the week tended to have real GABA surges. For instance, the practitioner who had done yoga for a decade experienced a GABA rise of 47 percent. One participant who practiced yoga five times a week had an increase of 80 percent, the levels of the neurotransmitter almost doubling.

The scientists concluded that yoga showed much promise for treating anxiety and depression. Perry F. Renshaw, a senior author of the study and director of brain imaging at the McLean Hospital, noted with understatement that any proven therapy that is cheap, widely available, and shows no side effects has “clear public health advantages.”

Encouraged, the team embarked on a new study. This time the scientists looked at nineteen subjects and a control group of fifteen people who walked for exercise, which was seen as having the same metabolic expenditure as yoga. The main subjects had no significant yoga experience. They learned the Iyengar style from scratch and practiced it for three months.

The findings were published in 2010. They showed that even beginning yogis experienced major rises in the neurotransmitter along with improved moods and lessened anxiety. The average GABA rise was less than in the previous study—13 percent versus 27 percent, or about half as much. Still, the new yogis did better than the walkers. And, judging from the evidence, they felt much better about themselves.