Yoga benefits, as ancient yoga books teach, are in breathing less air automatically and 24/7, even less than the tiny medical respiratory norm. Then one can expect more oxygen in the brain and other organs, and experience true benefits from yoga. Millions of people think and believe in a myth that yoga progress is about more and more difficult asanas or spiritual enlightenment. However, one can start yoga for beginners and can practice asanas for months or years, but this does not provide any guarantee that your health is going to improve. You can eat tons of supplements and super-foods, drink canisters of herbal drinks, have hundreds of colonic irrigations, and practice yoga for many hours every day, but if your body oxygen level remains the same, you will suffer from the same symptoms and require the same dosage of medication. You can also have years of spiritual practices while getting sicker and sicker with cancer, diabetes, weight gain and some other conditions. Only 2-3 generations ago, yoga did cure chronic diseases. Old American health journals and yoga books from the 1920's and 30's were full of advertisements of yoga courses with money back guarantees. Those yoga courses were for people with asthma, hypertension, chronic fatigue, weight loss, insomnia and other common conditions who successfully restored their health with old, traditional yoga. The main yoga benefit relates to better body oxygenation or correct automatic breathing. If you get this yoga benefit, all other benefits will follow. Then you can get an astonishing level of energy, perfect digestion, excellent sleep, and greatly improved physical fitness. Why could modern yoga teachers not replicate the same success? What is wrong or different in contemporary yoga leaders and their teaching of yoga for beginners and masters? Why most yoga courses provide almost no benefits to yoga students for weight loss and other conditions? Modern yoga teachers cannot explain, in exact numbers, the ideal breathing pattern that provides maximum body O2 levels. What do they say? Most yoga teachers claim that we need to breathe more air (even at rest) and expel "toxic" CO2. Modern science testify about solid physiological foundation of ancient yoga: when we breathe more air at rest (hyperventilation), we have less O2 in body cells. Breathing more air does not increase blood oxygenation to any significant degree. A person can breathe twice less or several times more than the medical norm, but blood oxygenation will be about the same, or about 97-99 %. But CO2 is the crucial factor for O2 transport. The book explains why slow and small breathing (with more CO2) provides more O2 for the cells. Thousands of recent research studies have proven beyond all doubts that chronic health problems, on a cell level, are based on low O2 levels. This relates to heart disease, cancer, diabetes, obesity, arthritis, inflammatory conditions, cystic fibrosis, HIV-AIDS and many other conditions. You cannot have normal body oxygenation and a lifestyle disease. Therefore, freedom from diseases is among main yoga health benefits. There are also hundreds of research studies that measured breathing of healthy people, ordinary people and people with chronic diseases. Dozens of these studies and their exact results are quoted in this book. These studies testify about the triumph of ancient yoga and its benefits. Deep breathing, as during pranayama, only looks deep. In reality, pranayama should be done with maximum breath holds and accumulation of CO2 in order to have slower breathing after the practice and 24/7. Only with progress in pranayama, one can get main yoga benefits. Progress in yoga for beginners and masters can be measured using a simple DIY body-oxygen test that is described in this book. If you get over 40 seconds of O2 for this easy test, then you will be astonished with changes in your health and real yoga benefits.