Today join me in welcoming Matthew Papaconstantinou from Weight Loss Triumph as he surveys decades of research into the weight loss and heart health benefits of yoga.
When you hear the advice that “diet and exercise are the keys to weight loss,” you probably think of running, kick-boxing, aerobics, or speed walking as the kind of exercise being recommended. But what about yoga? Isn’t it just about flexibility?
Actually, scientific studies published over three decades indicate that yoga may be a good choice as an exercise to help reduce risk for cardiovascular disease and for insulin resistance syndrome (IRS, also known as metabolic disorder, is a combination of medical disorders related to metabolism that increase the risk for cardiovascular disease).
Researchers at the Center for the Study of Complementary and Alternative Therapies at the University of Virginia Health Systems, led by Dr. Kim Innes, reviewed clinical studies published between 1970 and 2004 that evaluated the effects of yoga on cardiovascular disease and IRS. While Innes and her team concluded that there were some limitations in the way most of the studies were conducted, the results were generally quite positive, suggesting that yoga can reduce the factors for cardiovascular disease and IRS.
As a researcher working on cardiovascular-related diseases, with a personal interest in best diet programs for weight loss, I’m fascinated by these findings, which suggest that one of the oldest forms of intentional exercise might help us meet a lot of our health-related goals.
Cardiovascular Disease, IRS, and Obesity
The leading cause of premature death and disease in the U.S. and other industrialized countries is cardiovascular disease. Insulin resistance syndrome (IRS or metabolic syndrome) is a cluster of symptoms including insulin resistance, glucose intolerance, elevated levels of bad cholesterol, high blood pressure, and belly fat.
The various components of metabolic disorder are associated with increased risk of cardiovascular disease, and they are also associated in a complicated circle of cause and effect with lifestyle characteristics such as poor eating habits, smoking, and lack of exercise. Obese individuals often have metabolic disorder, and whether the disorder then feeds the obesity and the risk of cardiovascular disease.
In addition, recent research has suggested that chronic stress and negative emotion are also implicated in the cycle (causing bad lifestyle habits and perhaps even contributing to the development of metabolic syndrome).
Yoga: An Attractive Option for Intervening in the IRS-Obesity-Cardiovascular Disease Cycle
Yoga has been used in India since ancient times for the management of high blood pressure, diabetes, and related physical disorders. It is a mind-body discipline, involving meditation, controlled breathing, strength, and flexibility. There are a variety of types of yoga. If you’re thinking of yoga in the U.S. in the 1970s, you’re thinking of Mantra yoga, popularized by Maharishi Mahesh Yogi, the founder of Transcendental Meditation. Also popular in the U.S. today are Hatha yoga (also known as forceful yoga) and Raja yoga (classical yoga).
Yoga is safe, easy to learn, and can be practiced even by people with limited mobility. It doesn’t require much of anything in the way of specialized equipment, and overall, it is a form of exercise that once begun is well maintained.
The Virginia Study of Yoga, CVD, and IRS
Innes and the other researchers at the Center for the Study of Complementary and Alternative Therapies knew there was evidence that yoga could aid in reducing or improving metabolic syndrome and cardiovascular disease, including the risk of early death from cardiovascular disease, but they also found that no one had conducted a systematic review of the studies (a standard way scientists start to draw conclusions from research).
They did a systematic review of the research published between 1970 and 2004, and they including studies that evaluated the effects of yoga on various components of metabolic syndrome, including insulin resistance, cholesterol levels, body weight or BMI, blood pressure, and other medical signs of cardiovascular health. They found a total of 70 studies, most of them published between 1990 and 2004. The results were encouraging.
Effects of Yoga on Insulin Resistance
Insulin resistance is a condition in which cells fail to take up and use glucose for energy and metabolism. As I’ve noted, it’s a key component of metabolic disorder, which is implicated in obesity and cardiovascular disease. The Virginia researchers found a number of studies that evaluated the effects of yoga on insulin resistance.
Specifically, they found that studies using controls (that is, studies that compare the effects of the treatment to the effects on another group that did not receive the treatment) found that patients who practiced yoga experienced improvements in their levels of fasting glucose, glucose measured after a meal, and glycohemoglobin (a form of hemoglobin formed when high levels of glucose are available in the blood), all indicators of insulin resistance. Results for fasting glucose varied from a modest average 5.4% decrease to a whopping 33.4% decrease.
The researchers also found significant clinical results indicating that yoga has positive effects on lipid profiles, reducing LDL (bad cholesterol) and triglyceride levels and increasing HDL (good cholesterol). Results varied, but were as strong as an average decrease of 25.2% decrease in total cholesterol.
Weight Loss and Body Composition
A number of the studies reported favorable effects on weight and body composition following yoga programs lasting between a month and a year. The average weight loss ranged between 1.5% and 13.6% reduction in body weight.
The researchers found that most of the clinical studies had focused on the effects of yoga on blood pressure. Over 75% of the studies that evaluated effects on blood pressure found significant improvements in blood pressure with yoga. The studies that found these improvements in blood pressure were based on yoga programs lasting between a month and a year. Even the short-term studies found meaningful reductions in blood pressure.
Antioxidants and Free Radicals
The researchers also examined the reported effects of yoga on oxidative stress. Oxidative stress is the process that doctors are trying to counteract when they tell you to eat your green leafy vegetables or take antioxidant vitamins: the production of free radicals, those highly reactive molecules that damage proteins, membranes and genes.
Yoga, according to the published research, reduces oxidative stress by increasing antioxidants.
Effect of Yoga on Cardio-Respiratory Function and the Vagus Nerve
A number of studies over the years have focused on the effect of yoga on the vagus nerve, which regulates the activity of the lungs and heart. Yoga stimulates the vagus nerve and helps to reduce heart rate and blood pressure. Studies have found effects including reductions in cortisol (the “stress hormone”), reductions in catecholamine (“fight-or-flight” hormones), and other measures of stress on the heart and body, including heart rate and rate of respiration.
Psychosocial Risk Factors
Chronic stress and depression, through mechanisms that are only beginning to be understood, also effect cardiovascular health. The studies reviewed by the Virginia team provide evidence that yoga is also a positive force in reducing these psychosocial risk factors. Yoga has been reported to decrease perceived stress and reactivity to stressors, enhance stress-related coping, reduce symptoms of depression and anxiety, and decrease anger, tension, and tiredness. Yoga may also improve sleep.
The Bottom Line
It’s all good: yoga, an easy, inexpensive form of exercise with very low risk of injury, can be used to improve various aspects of metabolic disorder, including glucose tolerance, insulin sensitivity, lipid profiles, weight and body composition, blood pressure, vagal function, and stress and anxiety. While the researchers call for more tightly controlled studies to fine-tune the results, the research since 1970 strongly suggests that yoga is a good option for those looking to lose weight and improve their cardiovascular health.
As a researcher whose work is funded by the American Heart Association, Matthew Papaconstantinou maintains a web site where he regularly publishes news from the scientific findings about weight loss; his site also provides a free online personal counter for calories and offers a Medifast diet discount. Matt is currently a postdoctoral research fellow at Washington University School of Medicine in St. Louis, MO.