Unintentional weight loss can occur because of an inadequately nutritious diet relative to a person's energy needs (generally called malnutrition). Disease processes, changes in metabolism, hormonal changes, medications or other treatments, disease- or treatment-related dietary changes, or reduced appetite associated with a disease or treatment can also cause unintentional weight loss.[25][26][27][31][32][33] Poor nutrient utilization can lead to weight loss, and can be caused by fistulae in the gastrointestinal tract, diarrhea, drug-nutrient interaction, enzyme depletion and muscle atrophy.[27]
Many patients will be in pain and have a loss of appetite after surgery.[25] Part of the body's response to surgery is to direct energy to wound healing, which increases the body's overall energy requirements.[25] Surgery affects nutritional status indirectly, particularly during the recovery period, as it can interfere with wound healing and other aspects of recovery.[25][29] Surgery directly affects nutritional status if a procedure permanently alters the digestive system.[25] Enteral nutrition (tube feeding) is often needed.[25] However a policy of 'nil by mouth' for all gastrointestinal surgery has not been shown to benefit, with some suggestion it might hinder recovery.[37][needs update]

Unintentional weight loss may result from loss of body fats, loss of body fluids, muscle atrophy, or even a combination of these.[25][26] It is generally regarded as a medical problem when at least 10% of a person's body weight has been lost in six months[25][27] or 5% in the last month.[28] Another criterion used for assessing weight that is too low is the body mass index (BMI).[29] However, even lesser amounts of weight loss can be a cause for serious concern in a frail elderly person.[30]
This period also saw the rise of anabolic steroids in bodybuilding and many other sports. In bodybuilding lore, this is partly attributed to the rise of "mass monsters", beginning with Arnold Schwarzenegger, Sergio Oliva, and Lou Ferrigno in the late 1960s and early 1970s, and continuing through the 1980s with Lee Haney, the 1990s with Dorian Yates, Ronnie Coleman, and Markus Rühl, and up to the present day. Bodybuilders such as Greg Kovacs attained mass and size never seen previously but were not successful at the pro level. Others were renowned for their spectacular development of a particular body part, like Tom Platz or Paul Demayo for their leg muscles. At the time of shooting Pumping Iron, Schwarzenegger (while never admitting to steroid use until long after his retirement) said that "you have to do anything you can to get the advantage in competition".[citation needed] He would later say that he does not regret using anything.[8]
An increase in fiber intake is also recommended for regulating bowel movements. Other methods of weight loss include use of drugs and supplements that decrease appetite, block fat absorption, or reduce stomach volume. Bariatric surgery may be indicated in cases of severe obesity. Two common bariatric surgical procedures are gastric bypass and gastric banding.[12] Both can be effective at limiting the intake of food energy by reducing the size of the stomach, but as with any surgical procedure both come with their own risks[13] that should be considered in consultation with a physician. Dietary supplements, though widely used, are not considered a healthy option for weight loss.[14] Many are available, but very few are effective in the long term.[15] https://www.facebook.com/Business-Insights-1341803259306201/