Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue or lean mass, namely bone mineral deposits, muscle, tendon, and other connective tissue. Weight loss can either occur unintentionally due to malnourishment or an underlying disease or arise from a conscious effort to improve an actual or perceived overweight or obese state. "Unexplained" weight loss that is not caused by reduction in calorific intake or exercise is called cachexia and may be a symptom of a serious medical condition. Intentional weight loss is commonly referred to as slimming.
Genetics, or inherited traits from parents, also play a role in determining the health status of individuals and populations. This can encompass both the predisposition to certain diseases and health conditions, as well as the habits and behaviors individuals develop through the lifestyle of their families. For example, genetics may play a role in the manner in which people cope with stress, either mental, emotional or physical. For example, obesity is a significant problem in the United States that contributes to bad mental health and causes stress in the lives of great numbers of people. (One difficulty is the issue raised by the debate over the relative strengths of genetics and other factors; interactions between genetics and environment may be of particular importance.)
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. Health and illness can co-exist, as even people with multiple chronic diseases or terminal illnesses can consider themselves healthy.
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.
During the Gupta period (4th to 5th centuries), a movement of northern Mahāyāna Buddhism termed Yogācāra began to be systematized with the writings of the Buddhist scholars Asanga and Vasubandhu. Yogācāra Buddhism received the name as it provided a "yoga," a systematic framework for engaging in the practices that lead through the path of the bodhisattva towards awakening and full Buddhahood. Its teachings can be found in the comprehensive and encyclopedic work, the Yogācārabhūmi-Śāstra (Treatise on the Foundation for Yoga Practitioners), which was also translated into Tibetan and Chinese and thus exerted a profound influence on the East Asian Buddhist and Tibetan Buddhist traditions. According to Mallinson and Singleton, the study of Yogācāra Buddhism is essential for the understanding of yoga's early history, and its teachings influenced the text of the Pātañjalayogaśāstra.
Public health also takes various actions to limit the health disparities between different areas of the country and, in some cases, the continent or world. One issue is the access of individuals and communities to health care in terms of financial, geographical or socio-cultural constraints to accessing and using services. Applications of the public health system include the areas of maternal and child health, health services administration, emergency response, and prevention and control of infectious and chronic diseases.
During the period between the Mauryan and the Gupta eras (c. 200 BCE–500 CE) the Indic traditions of Hinduism, Buddhism and Jainism were taking form and coherent systems of yoga began to emerge. This period witnessed many new texts from these traditions discussing and systematically compiling yoga methods and practices. Some key works of this era include the Yoga Sūtras of Patañjali, the Yoga-Yājñavalkya, the Yogācārabhūmi-Śāstra and the Visuddhimagga.
Śaradatilaka of Lakshmanadesikendra, a Shakta Tantra work 11th century CE "Yogic experts state that yoga is the oneness of the individual soul (jiva) with the atman. Others understand it to be the ascertainment of Siva and the soul as non-different. The scholars of the Agamas say that it is a Knowledge which is of the nature of Siva’s Power. Other scholars say it is the knowledge of the primordial soul." (SaTil 25.1–3b)
An influential text which teaches yoga from an Advaita perspective of nondualistic idealism is the Yoga-Vāsiṣṭha. This work uses numerous short stories and anecdotes to illustrate its main ideas. It teaches seven stages or bhumis of yogic practice. It was a major reference for medieval Advaita Vedanta yoga scholars and before the 12th century, it was one of the most popular texts on Hindu yoga.
Ascetic practices, concentration and bodily postures described in the Vedas may have been precursors to yoga. According to Geoffrey Samuel, "Our best evidence to date suggests that [yogic] practices developed in the same ascetic circles as the early sramana movements (Buddhists, Jainas and Ajivikas), probably in around the sixth and fifth centuries BCE."
According to Tattvarthasutra, 2nd century CE Jain text, yoga is the sum of all the activities of mind, speech and body. Umasvati calls yoga the cause of "asrava" or karmic influx as well as one of the essentials—samyak caritra—in the path to liberation. In his Niyamasara, Acarya Kundakunda, describes yoga bhakti—devotion to the path to liberation—as the highest form of devotion. Acarya Haribhadra and Acarya Hemacandra mention the five major vows of ascetics and 12 minor vows of laity under yoga. This has led certain Indologists like Prof. Robert J. Zydenbos to call Jainism, essentially, a system of yogic thinking that grew into a full-fledged religion. The five yamas or the constraints of the Yoga Sutras of Patanjali bear a resemblance to the five major vows of Jainism, indicating a history of strong cross-fertilization between these traditions.[note 16]
Yoga may have pre-Vedic elements. Some state yoga originated in the Indus Valley Civilization. Marshall, Eliade 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 and may be a case of projecting "later practices into archeological findings".
Continuing weight loss may deteriorate into wasting, a vaguely defined condition called cachexia. Cachexia differs from starvation in part because it involves a systemic inflammatory response. It is associated with poorer outcomes. In the advanced stages of progressive disease, metabolism can change so that they lose weight even when they are getting what is normally regarded as adequate nutrition and the body cannot compensate. This leads to a condition called anorexia cachexia syndrome (ACS) and additional nutrition or supplementation is unlikely to help. Symptoms of weight loss from ACS include severe weight loss from muscle rather than body fat, loss of appetite and feeling full after eating small amounts, nausea, anemia, weakness and fatigue.
Health, as defined by the World Health Organization (WHO), is "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity." This definition has been subject to controversy, as it may have limited value for implementation. Health may be defined as the ability to adapt and manage physical, mental and social challenges throughout life.
The focus of public health interventions is to prevent and manage diseases, injuries and other health conditions through surveillance of cases and the promotion of healthy behavior, communities, and (in aspects relevant to human health) environments. Its aim is to prevent health problems from happening or re-occurring by implementing educational programs, developing policies, administering services and conducting research. In many cases, treating a disease or controlling a pathogen can be vital to preventing it in others, such as during an outbreak. Vaccination programs and distribution of condoms to prevent the spread of communicable diseases are examples of common preventive public health measures, as are educational campaigns to promote vaccination and the use of condoms (including overcoming resistance to such).