by Sandeep (Anu) Kaur, MS, RDN, RYT-500 and Sat Bir Khalsa, Ph.D
Obesity, defined as a Body Mass Index (BMI) of 30 or greater, is an epidemic in the US and a pivotal link between increased risk of cardiovascular disease, cancer, and other chronic diseases. Yoga, a mind-body approach, has been increasingly practiced for improving overall health. Most yoga practitioners indicate that the top reason for starting a yoga practice is to improve their health and manage weight. Yoga’s goal of “union of mind-body-spirit” along with the utilization of physical postures, breathing techniques, deep relaxation, and meditative/mindfulness practices offers an internal self-contemplative state that differentiates yoga from conventional exercise such as strength/weight training or aerobic exercise.
Previous studies have established that despite initial psychological and physiological benefits from traditional diet and exercise programs, these weight loss strategies and other conventional medical treatments are relatively poor with respect to long-term adherence to healthy lifestyle changes. This remains a major barrier and weakness in these conventional health approaches. A number of different healthy behaviors are known to influence weight control such as increased exercise, decreased meal portions, and decreased fat and sugar intake. As a form of fat-burning exercise, preliminary clinical trials suggest that yoga practice may or may not contribute strongly to cardiovascular fitness, depending upon the specific yoga style and physical exercises practiced. More recently, research has been conducted on the role of increased mind-body awareness which is connected to both mindful eating behavior and body image awareness.
Most lineages/styles of yoga engender greater body awareness that is associated with a healthier relationship with food and greater body satisfaction. There is also a relationship between chronic stress and weight regulation. Evidence indicates that activation of the stress system is associated with increased consumption of high fat, high sugar foods, and abdominal weight gain. This may be due to increased hypothalamic-pituitary adrenal axis stimulation that elevates levels of the stress hormone cortisol and the activation of the autonomic nervous system (enhanced sympathetic activity and release of adrenaline and reduction of parasympathetic vagal activity). It is well known that yoga is highly effective for regulation of these stress systems, and therefore may mitigate stress-induced binge eating and poor dietary choices (such as so-called comfort foods) that are high in carbohydrates, sugar, and fat. These beneficial psychophysiological characteristics with respect to weight regulation likely account for the observation that regular practitioners of integrative, complementary, and mind-body techniques, including yoga, report healthier weight regulation.
With respect to broader populations, a 2014 study at Columbia University looked at associations between lifestyle behaviors such as dietary changes, conventional supplement use, exercise, and complementary modalities such as yoga. They found those that those using complementary and alternative medicine (CAM) were 4.7 times more likely to engage in healthy lifestyle behaviors than individuals not using CAM. More recently in 2016, in a large sample of internet-using adult volunteers in France, a study examined if practice of any mind-body technique was associated with weight. This study found that 13.8% of the general population were practicing a mind-body modality and the most common practices were meditation (7.6%) and yoga (4.8%) with 7.9% regular users and 5.8% occasional users. Consistent mind-body technique users were the least likely to be obese or overweight. These associations suggest that CAM users (who include a large proportion of mind-body and yoga practitioners) may be a population committed to overall wellness. More specific to yoga, there are now a number of studies examining subpopulations of yoga practitioners with respect to weight regulation.
In a large observational study, Dr. Emily White, Dr. Alan R. Kristal, and colleagues at the University of Washington were one of the first to retrospectively examine the relationship between weight and yoga practice in healthy men and women between the ages of 53 to 57 from the national Vitamins and Lifestyle study (VITAL) with 15,550 participants in 2000-2002. A relatively small number of individuals reported having a yoga practice 7.5% (n=1,039), a statistic similar to that from the national yoga prevalence reported in the national cross-sectional 2002 National Health Interview Survey (NHIS). They found yoga practice during the previous 10 years, since age 45, was associated with attenuated weight gain as compared with non-practitioners for those who were overweight or obese. There were also significant trends for healthier diet patterns and more physical activity in yoga practitioners than in non-yoga practitioners.
Yoga researcher Gurjeet Birdee, MD and colleagues examined the NHIS survey data from 2002 to evaluate yoga’s use for health. They found yoga practitioners were more likely to be healthy and fewer were obese, with most yoga users reporting yoga as significant in maintaining their overall health. Similarly, a more recent study of the prevalence, trends, and correlates of yoga practice in England between 1997 and 2008, using the Health Survey for England data, found that those practicing yoga (as defined by any yoga practice in the last 4 weeks) had a lower BMI, better self-rated general health, and reported a higher frequency of moderate-to-vigorous level of physical activity. Other studies have directly and specifically approached and examined yoga practitioners.
Yoga researcher Nina Moliver and colleagues using an internet survey assessed whether long term yoga practice was associated with BMI in middle-aged women. They interviewed 211 female yoga practitioners (ages 45 to 80) to evaluate if BMI varied based on the length and frequency of their yoga practice. They found a significant inverse relationship such that an increase in yoga experience predicted a lower BMI. Additionally, 49 individuals who had 25 or more years of yoga practice had no obesity. Furthermore, a comparison of the yoga practitioners with general population values of those with similar age and gender revealed a lower BMI in the yoga practitioners.
Perhaps the best research of this kind has been conducted recently by Alyson Ross and colleagues at the National Institutes of Health. They conducted a national survey of American yoga practitioners and observed that higher frequency of practice was associated with decreased BMI. Rather than years of yoga practice or class participation, it was frequency of yoga practice outside of class that was repeatedly a predictor of facets of health including BMI, fruit and vegetable consumption, mindfulness, and subjective well-being.