In medicine, health, or physical fitness, weight loss is a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other connective tissue). Weight loss can either occur unintentionally because of malnourishment or an underlying disease, or 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 increase in exercise is called cachexia and may be a symptom of a serious medical condition.

Description

Weight loss typically occurs when fewer calories are consumed (also known as a caloric deficit) than is expended by daily activities, physiological processes and physical exercise. If enough weight is lost due to a reduction in body fat, an individual may move from being overweight (25.0-29.9) or obese (30+) into a healthy weight range (18.5-24.9); however, continued weight loss beyond this point can lead to becoming underweight (< 18.5).

Intentional

Intentional weight loss is the loss of total body mass as a result of efforts to improve fitness and health, or to change appearance through slimming. Weight loss is the main treatment for obesity,

Weight loss in individuals who are overweight or obese can reduce health risks, and may delay the onset of diabetes. It could reduce pain and increase movement in people with osteoarthritis of the knee. Depression, stress or boredom may contribute to unwanted weight gain or loss depending on the individual, and in these cases, individuals are advised to seek medical help. A 2010 study found that dieters who got a full night's sleep lost more than twice as much fat as sleep-deprived dieters. Though hypothesized that supplementation of vitamin D may help, studies do not support this. The majority of dieters regain weight over the long term. According to the UK National Health Service and the Dietary Guidelines for Americans, those who achieve and manage a healthy weight do so most successfully by being careful to consume just enough calories to meet their needs, and being physically active. There is evidence that counseling or exercise alone do not result in weight loss, whereas dieting alone results in meaningful long-term weight loss, and a combination of dieting and exercise provides the best results. Meal replacements, orlistat, a very-low-calorie diet, and primary care intensive medical interventions can also support meaningful weight loss.

Techniques

thumb|alt=The cardboard packaging of two medications used to treat obesity. Orlistat is shown above under the brand name Xenical in a white package with Roche branding. Sibutramine is below under the brand name Meridia. Orlistat is also available as Alli in the United Kingdom. The A of the Abbott Laboratories logo is on the bottom half of the package.|right|[[Orlistat (Xenical), a commonly used anti-obesity medication, and sibutramine (Meridia), a withdrawn medication due to cardiovascular side effects]]

Diet and exercise

The least intrusive weight loss methods, and those most often recommended, are adjustments to eating patterns and increased physical activity, generally in the form of exercise. Weight training has been recommended as a type of exercise to burn fat, because of its ability to increase muscle mass, which increases metabolism. The World Health Organization recommends that people combine a reduction of processed foods high in saturated fats, sugar and salt, and reduced caloric intake with an increase in physical activity. Both long-term exercise programs and anti-obesity medications reduce abdominal fat volume.

Self-monitoring of diet, exercise, and weight are beneficial strategies for weight loss, particularly early in weight loss programs. Research indicates that those who log their foods about three times per day and about 20 times per month are more likely to achieve clinically significant weight loss.

Permanent weight loss depends on maintaining a negative energy balance and not the type of macronutrients (such as carbohydrate) consumed. High protein diets have shown greater efficacy in the short term (under 12 months) for people eating ad libitum due to increased thermogenesis and satiety, however this effect tends to dissipate over time.

Hydration

Increasing water intake can reduce weight by increasing thermogenesis, by reducing food intake, and by increasing fat oxidation. Persons dieting for weight loss have demonstrated the weight-reducing effects of increased water consumption. Among adults in the U.S. there is a significant association between inadequate hydration and obesity.

Medications

Other methods of weight loss include use of anti-obesity drugs that decrease appetite, block fat absorption, or reduce stomach volume. Obesity has been resistant to drug-based therapies, with a 2021 review stating that existing medications are "often delivering insufficient efficacy and dubious safety". Semaglutide has also become popular recently as an aid in weight loss. It is particularly beneficial for those with type 2 diabetes and obesity.

Bariatric surgery

Bariatric surgery may be indicated in cases of severe obesity. Two common bariatric surgical procedures are gastric bypass and gastric banding. 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 that should be considered in consultation with a physician.

Weight loss industry

There is a substantial market for products which claim to make weight loss easier, quicker, cheaper, more reliable, or less painful. These include books, DVDs, CDs, cremes, lotions, pills, rings and earrings, body wraps, body belts and other materials, fitness centers, clinics, personal coaches, weight loss groups, and food products and supplements. Dietary supplements, though widely used, are not considered a healthy option for weight loss, and have no clinical evidence of efficacy. Herbal products have not been shown to be effective.

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 per year was spent on weight-loss supplements. About 70 percent of Americans' dieting attempts are of a self-help nature.

The scientific soundness of commercial diets by commercial weight management organizations varies widely, being previously non-evidence-based, so there is only limited evidence supporting their use, because of high attrition rates. Commercial diets result in modest weight loss in the long term, with similar results regardless of the brand, Comprehensive diet programs, providing counseling and targets for calorie intake, are more efficient than dieting without guidance ("self-help"), although the evidence is very limited. The National Institute for Health and Care Excellence devised a set of essential criteria to be met by commercial weight management organizations to be approved. Another criterion used for assessing weight that is too low is the body mass index (BMI).

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. 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. 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. In the UK, up to 5% of the general population is underweight, but more than 10% of those with lung or gastrointestinal diseases and who have recently had surgery. Wasting syndrome is an AIDS-defining condition. and many other GI conditions.

  • Infection. Some infectious diseases can cause weight loss. Fungal illnesses, endocarditis, many parasitic diseases, AIDS, Whipple's disease and some other subacute or occult infections may cause weight loss.
  • Renal disease. Patients who have uremia often have poor or absent appetite, vomiting and nausea. This can cause weight loss.
  • Cardiac disease. Cardiovascular disease, especially congestive heart failure, may cause unexplained weight loss.
  • Connective tissue disease
  • Oral, taste or dental problems (including infections) can reduce nutrient intake leading to weight loss. Surgery directly affects nutritional status if a procedure permanently alters the digestive system. Early post-operative nutrition is a part of Enhanced Recovery After Surgery protocols. These protocols also include carbohydrate loading in the 24 hours before surgery, but earlier nutritional interventions have not been shown to have a significant impact. Nutrient intake can also be affected by culture, family and belief systems. They also commented that the idea of changing one's rate of metabolism is under debate.

Health effects

Obesity is a risk factor for certain conditions, including diabetes, cancer, cardiovascular disease, high blood pressure, and non-alcoholic fatty liver disease. Reduction of obesity lowers those risks. A loss of body weight has been associated with an approximate drop in blood pressure. Intentional weight loss is associated with cognitive performance improvements in overweight and obese individuals.

See also

  • Anorexia
  • Cigarette smoking for weight loss
  • Weight gain

References

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  • Weight-control Information Network U.S. National Institutes of Health
  • Nutrition in cancer care, US National Library of Medicine