Alexander the Great reached India in the 4th century BCE. Along with his army, he took Greek academics with him who later wrote memoirs about geography, people and customs they saw. One of Alexander's companion was Onesicritus, quoted in Book 15, Sections 63–65 by Strabo, who describes yogins of India.[107] Onesicritus claims those Indian yogins (Mandanis ) practiced aloofness and "different postures – standing or sitting or lying naked – and motionless".[108]
^ * Wynne states that "The Nasadiyasukta, one of the earliest and most important cosmogonic tracts in the early Brahminic literature, contains evidence suggesting it was closely related to a tradition of early Brahminic contemplation. A close reading of this text suggests that it was closely related to a tradition of early Brahminic contemplation. The poem may have been composed by contemplatives, but even if not, an argument can be made that it marks the beginning of the contemplative/meditative trend in Indian thought."[73]
Personal health also depends partially on the social structure of a person's life. The maintenance of strong social relationships, volunteering, and other social activities have been linked to positive mental health and also increased longevity. One American study among seniors over age 70, found that frequent volunteering was associated with reduced risk of dying compared with older persons who did not volunteer, regardless of physical health status.[58] Another study from Singapore reported that volunteering retirees had significantly better cognitive performance scores, fewer depressive symptoms, and better mental well-being and life satisfaction than non-volunteering retirees.[59]

Yoga is discussed in the ancient foundational Sutras of Hindu philosophy. The Vaiśeṣika Sūtra of the Vaisheshika school of Hinduism, dated to have been composed sometime between 6th and 2nd century BCE discusses Yoga.[note 14] According to Johannes Bronkhorst, an Indologist known for his studies on early Buddhism and Hinduism and a professor at the University of Lausanne, Vaiśeṣika Sūtra describes Yoga as "a state where the mind resides only in the soul and therefore not in the senses".[120] This is equivalent to pratyahara or withdrawal of the senses, and the ancient Sutra asserts that this leads to an absence of sukha (happiness) and dukkha (suffering), then describes additional yogic meditation steps in the journey towards the state of spiritual liberation.[120]
In 1989 and 2003, the Vatican issued two documents: Aspects of Christian meditation and "A Christian reflection on the New Age," that were mostly critical of eastern and New Age practices. The 2003 document was published as a 90-page handbook detailing the Vatican's position.[286] The Vatican warned that concentration on the physical aspects of meditation "can degenerate into a cult of the body" and that equating bodily states with mysticism "could also lead to psychic disturbance and, at times, to moral deviations." Such has been compared to the early days of Christianity, when the church opposed the gnostics' belief that salvation came not through faith but through a mystical inner knowledge.[280] The letter also says, "one can see if and how [prayer] might be enriched by meditation methods developed in other religions and cultures"[287] but maintains the idea that "there must be some fit between the nature of [other approaches to] prayer and Christian beliefs about ultimate reality."[280] Some[which?] fundamentalist Christian organizations consider yoga to be incompatible with their religious background, considering it a part of the New Age movement inconsistent with Christianity.[288]

The Bhakti movement was a development in medieval Hinduism which advocated the concept of a personal God (or "Supreme Personality of Godhead"). The movement was initiated by the Alvars of South India in the 6th to 9th centuries, and it started gaining influence throughout India by the 12th to 15th centuries.[177] Shaiva and Vaishnava bhakti traditions integrated aspects of Yoga Sutras, such as the practical meditative exercises, with devotion.[178] Bhagavata Purana elucidates the practice of a form of yoga called viraha (separation) bhakti. Viraha bhakti emphasizes one pointed concentration on Krishna.[179]
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]
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]
These meditations were seen as being supported by the other elements of the eightfold path, such as the practice of ethics, right exertion, sense restraint and right view.[244] Two mental qualities are said to be indispensable for yogic practice in Buddhism, samatha (calm, stability) and vipassanā (insight, clear seeing).[245] Samatha is the quality of a stable, relaxed and calm mind. It is also associated with samadhi (mental unification, focus) and dhyana (a state of meditative absorption). Vipassanā meanwhile, is a kind of insight or penetrative understanding into the true nature of phenomena. It is also defined as "seeing things as they truly are" (yathābhūtaṃ darśanam). The true nature of things is defined and explained in different ways, but an important and unique feature of classical Buddhism is its understanding of all phenomena (dhammas) as being empty of a self (atman) or inherent essence, a doctrine termed Anatta ("not-self") and Śūnyatā (emptiness).[246][247] This is in sharp contrast with most other Indian traditions, whose goals are founded either on the idea of an individual soul (atman, jiva, purusha) or a universal monistic consciousness ( Brahman). Vipassanā also requires an understanding of suffering or dukkha (and thus the four noble truths), impermanence (anicca) and interdependent origination.
Vajrayana is also known as Tantric Buddhism and Tantrayāna. Its texts were compiled starting with 7th century and Tibetan translations were completed in 8th century CE. These tantra yoga texts were the main source of Buddhist knowledge that was imported into Tibet.[185] They were later translated into Chinese and other Asian languages, helping spread ideas of Tantric Buddhism. The Buddhist text Hevajra Tantra and Caryāgiti introduced hierarchies of chakras.[186] Yoga is a significant practice in Tantric Buddhism.[187][188][189]
The origins of yoga are a matter of debate.[44] There is no consensus on its chronology or specific origin other than that yoga developed in ancient India. Suggested origins are the Indus Valley Civilization (3300–1900 BCE)[45] and pre-Vedic Eastern states of India,[46] the Vedic period (1500–500 BCE), and the śramaṇa movement.[47] According to Gavin Flood, continuities may exist between those various traditions:

In Iran, as of May 2014, according to its Yoga Association, there were approximately 200 yoga centres in the country, a quarter of them in the capital Tehran, where groups can often be seen practising in parks. This has been met by opposition among conservatives.[305] In May 2009, Turkey's head of the Directorate of Religious Affairs, Ali Bardakoğlu, discounted personal development techniques such as reiki and yoga as commercial ventures that could lead to extremism. His comments were made in the context of reiki and yoga possibly being a form of proselytization at the expense of Islam.[306]
Focusing more on lifestyle issues and their relationships with functional health, data from the Alameda County Study suggested that people can improve their health via exercise, enough sleep, maintaining a healthy body weight, limiting alcohol use, and avoiding smoking.[27] Health and illness can co-exist, as even people with multiple chronic diseases or terminal illnesses can consider themselves healthy.[28]
‡The results presented here are from the combined studies supporting FDA approval of Qsymia. Qsymia was studied in 2 large trials that involved 3754 patients whose BMI was 27 kg/m2 or greater. The average baseline weight of the subjects in the 2 studies was 256 lbs and 227 lbs. Patients were randomized to placebo, phentermine 3.75 mg/topiramate 23 mg, phentermine 7.5 mg/topiramate 46 mg, or phentermine 15 mg/topiramate 92 mg.
In 2008 between US$33 billion and $55 billion was spent annually in the US on weight-loss products and services, including medical procedures and pharmaceuticals, with weight-loss centers taking between 6 and 12 percent of total annual expenditure. Over $1.6 billion a year was spent on weight-loss supplements. About 70 percent of Americans' dieting attempts are of a self-help nature.[23][24]