Yoga gurus from India later introduced yoga to the West,[16] following the success of Swami Vivekananda in the late 19th and early 20th century with his adaptation of yoga tradition, excluding asanas.[16] In the 1980s, a very different form of modern yoga, with an increasing number of asanas and few other practices, became popular as a system of exercise across the Western world.[15] Yoga in Indian traditions, however, is more than physical exercise; it has a meditative and spiritual core.[17] One of the six major orthodox schools of Hinduism is also called Yoga, which has its own epistemology and metaphysics, and is closely related to Hindu Samkhya philosophy.[18]
Samuel states that Tantrism is a contested concept.[182] Tantra yoga may be described, according to Samuel, as practices in 9th to 10th century Buddhist and Hindu (Saiva, Shakti) texts, which included yogic practices with elaborate deity visualizations using geometrical arrays and drawings (mandala), fierce male and particularly female deities, transgressive life stage related rituals, extensive use of chakras and mantras, and sexual techniques, all aimed to help one's health, long life and liberation.[182][265]
The first known appearance of the word "yoga", with the same meaning as the modern term, is in the Katha Upanishad,[10][95] probably composed between the fifth and third century BCE,[96][97] where it is defined as the steady control of the senses, which along with cessation of mental activity, leading to a supreme state.[67][note 13] Katha Upanishad integrates the monism of early Upanishads with concepts of samkhya and yoga. It defines various levels of existence according to their proximity to the innermost being Ātman. Yoga is therefore seen as a process of interiorization or ascent of consciousness.[99][100] It is the earliest literary work that highlights the fundamentals of yoga. White states:
"When going out for fast food, I used to get the large-size value meal. Now, I satisfy a craving by ordering just one item: a small order of fries or a six-piece box of chicken nuggets. So far, I've shaved off 16 pounds in seven weeks, and I'm on track to being thinner than my high school self for my 10-year reunion later this year." —Miranda Jarrell, Birmingham, AL
Personal health depends partially on the active, passive, and assisted cues people observe and adopt about their own health. These include personal actions for preventing or minimizing the effects of a disease, usually a chronic condition, through integrative care. They also include personal hygiene practices to prevent infection and illness, such as bathing and washing hands with soap; brushing and flossing teeth; storing, preparing and handling food safely; and many others. The information gleaned from personal observations of daily living – such as about sleep patterns, exercise behavior, nutritional intake and environmental features – may be used to inform personal decisions and actions (e.g., "I feel tired in the morning so I am going to try sleeping on a different pillow"), as well as clinical decisions and treatment plans (e.g., a patient who notices his or her shoes are tighter than usual may be having exacerbation of left-sided heart failure, and may require diuretic medication to reduce fluid overload).[57]

This terse definition hinges on the meaning of three Sanskrit terms. I. K. Taimni translates it as "Yoga is the inhibition (nirodhaḥ) of the modifications (vṛtti) of the mind (citta)".[142]Swami Vivekananda translates the sutra as "Yoga is restraining the mind-stuff (Citta) from taking various forms (Vrittis)."[143] Edwin Bryant explains that, to Patanjali, "Yoga essentially consists of meditative practices culminating in attaining a state of consciousness free from all modes of active or discursive thought, and of eventually attaining a state where consciousness is unaware of any object external to itself, that is, is only aware of its own nature as consciousness unmixed with any other object."[144][145][146]
Gastrointestinal disorders are another common cause of unexplained weight loss – in fact they are the most common non-cancerous cause of idiopathic weight loss.[citation needed] Possible gastrointestinal etiologies of unexplained weight loss include: celiac disease, peptic ulcer disease, inflammatory bowel disease (crohn's disease and ulcerative colitis), pancreatitis, gastritis, diarrhea and many other GI conditions.
According to Geoffrey Samuel, our "best evidence to date" suggests that yogic practices "developed in the same ascetic circles as the early śramaṇa movements (Buddhists, Jainas and Ajivikas), probably in around the sixth and fifth centuries BCE." This occurred during what is called the ‘Second Urbanisation’ period.[9] According to Mallinson and Singleton, these traditions were the first to use psychophysical techniques, mainly known as dhyana and tapas. but later described as yoga, to strive for the goal of liberation (moksha, nirvana) from samsara (the round of rebirth).[78]
Virtual gastric band uses hypnosis to make the brain think the stomach is smaller than it really is and hence lower the amount of food ingested. This brings as a consequence weight reduction. This method is complemented with psychological treatment for anxiety management and with hypnopedia. Research has been conducted into the use of hypnosis as a weight management alternative.[16][17][18][19] In 1996 a study found that cognitive-behavioral therapy (CBT) was more effective for weight reduction if reinforced with hypnosis.[17] Acceptance and Commitment Therapy ACT, a mindfulness approach to weight loss, has also in the last few years been demonstrating its usefulness.[20]
Pre-philosophical speculations of yoga begin to emerge in the texts of c. 500 – c. 200 BCE. Between 200 BCE and 500 CE, philosophical schools of Hinduism, Buddhism, and Jainism were taking form and a coherent philosophical system of yoga began to emerge.[50] The Middle Ages saw the development of many satellite traditions of yoga. Yoga came to the attention of an educated western public in the mid 19th century along with other topics of Indian philosophy.

In the early 11th century, the Persian scholar Al Biruni visited India, lived with Hindus for 16 years, and with their help translated several significant Sanskrit works into Arabic and Persian languages. One of these was Patanjali's Yogasutras.[290][291] Al Biruni's translation preserved many of the core themes of Patañjali 's Yoga philosophy, but certain sutras and analytical commentaries were restated making it more consistent with Islamic monotheistic theology.[290][292] Al Biruni's version of Yoga Sutras reached Persia and Arabian peninsula by about 1050 AD. Later, in the 16th century, the hath yoga text Amritakunda was translated into Arabic and then Persian.[293] Yoga was, however, not accepted by mainstream Sunni and Shia Islam. Minority Islamic sects such as the mystic Sufi movement, particularly in South Asia, adopted Indian yoga practises, including postures and breath control.[294][295] Muhammad Ghawth, a Shattari Sufi and one of the translators of yoga text in 16th century, drew controversy for his interest in yoga and was persecuted for his Sufi beliefs.[296]
The hymns in Book 2 of the Shvetashvatara Upanishad, another late first millennium BCE text, states a procedure in which the body is held in upright posture, the breath is restrained and mind is meditatively focussed, preferably inside a cave or a place that is simple, plain, of silence or gently flowing water, with no noises nor harsh winds.[102][103][100]
Classical yoga incorporates epistemology, metaphysics, ethical practices, systematic exercises and self-development techniques for body, mind and spirit.[144] Its epistemology (pramana) and metaphysics is similar to that of the Sāṅkhya school. The metaphysics of Classical Yoga, like Sāṅkhya, is mainly dualistic, positing that there are two distinct realities. These are prakriti (nature), which is the eternal and active unconscious source of the material world and is composed of three gunas, and the puruṣas (persons), the plural consciousnesses which are the intelligent principles of the world, and are multiple, inactive and eternal witnesses. Each person has a individual puruṣa, which is their true self, the witness and the enjoyer, and that which is liberated. This metaphysical system holds that puruṣas undergo cycles of reincarnation through its interaction and identification with prakirti. Liberation, the goal of this system, results from the isolation (kaivalya) of puruṣa from prakirti, and is achieved through a meditation which detaches oneself from the different forms (tattvas) of prakirti.[240] This is done by stilling one's thought waves (citta vritti) and resting in pure awareness of puruṣa.
Sleep is an essential component to maintaining health. In children, sleep is also vital for growth and development. Ongoing sleep deprivation has been linked to an increased risk for some chronic health problems. In addition, sleep deprivation has been shown to correlate with both increased susceptibility to illness and slower recovery times from illness.[47] In one study, people with chronic insufficient sleep, set as six hours of sleep a night or less, were found to be four times more likely to catch a cold compared to those who reported sleeping for seven hours or more a night.[48] Due to the role of sleep in regulating metabolism, insufficient sleep may also play a role in weight gain or, conversely, in impeding weight loss.[49] Additionally, in 2007, the International Agency for Research on Cancer, which is the cancer research agency for the World Health Organization, declared that "shiftwork that involves circadian disruption is probably carcinogenic to humans," speaking to the dangers of long-term nighttime work due to its intrusion on sleep.[50] In 2015, the National Sleep Foundation released updated recommendations for sleep duration requirements based on age and concluded that "Individuals who habitually sleep outside the normal range may be exhibiting signs or symptoms of serious health problems or, if done volitionally, may be compromising their health and well-being."[51]
Yoga may have pre-Vedic elements.[45][46] Some state yoga originated in the Indus Valley Civilization.[51] Marshall,[52] Eliade[10] and other scholars note that the Pashupati seal discovered in an Indus Valley Civilization site depicts a figure in a position resembling an asana used for meditation, Mulabandhasana. This interpretation is considered speculative and uncertain by more recent analysis of Srinivasan[10] and may be a case of projecting "later practices into archeological findings".[53]
The earliest extant systematic account of yoga and a bridge from the earlier Vedic uses of the term is found in the Hindu Katha Upanisad (Ku), a scripture dating from about the third century BCE[…] [I]t describes the hierarchy of mind-body constituents—the senses, mind, intellect, etc.—that comprise the foundational categories of Sāmkhya philosophy, whose metaphysical system grounds the yoga of the Yogasutras, Bhagavad Gita, and other texts and schools (Ku3.10–11; 6.7–8).[101]
"When going out for fast food, I used to get the large-size value meal. Now, I satisfy a craving by ordering just one item: a small order of fries or a six-piece box of chicken nuggets. So far, I've shaved off 16 pounds in seven weeks, and I'm on track to being thinner than my high school self for my 10-year reunion later this year." —Miranda Jarrell, Birmingham, AL