|Classification and external resources|
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 and/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.
Unintentional weight loss may result from loss of body fats, loss of body fluids, muscle atrophy, or even a combination of these. It is generally regarded as a medical problem when at least 10% of a person's body weight has been lost in six months or 5% in the last month. Another criterion used for assessing weight that is too low is the body mass index (BMI). However, even lesser amounts of weight loss can be a cause for serious concern in a frail elderly person.
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.
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.
Serious weight loss may reduce quality of life, impair treatment effectiveness or recovery, worsen disease processes and be a risk factor for high mortality rates. Malnutrition can affect every function of the human body, from the cells to the most complex body functions, including:
- immune response;
- wound healing;
- muscle strength (including respiratory muscles);
- renal capacity and depletion leading to water and electrolyte disturbances;
- thermoregulation; and
Unintentional weight loss can be the characteristic leading to diagnosis of diseases such as cancer and type 1 diabetes.
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. According to data in the UK using the Malnutrition Universal Screening Tool ('MUST'), which incorporates unintentional weight loss, more than 10% of the population over the age of 65 is at risk of malnutrition. A high proportion (10-60%) of hospital patients are also at risk, along with a similar proportion in care homes.
|Impaired intake|| Poor appetite can be a direct symptom of an illness, or an illness could make eating painful or induce nausea. Illness can also cause food aversion.
Inability to eat can result from: diminished consciousness or confusion, or physical problems affecting the arm or hands, swallowing or chewing. Eating restrictions may also be imposed as part of treatment or investigations. Lack of food can result from: poverty, difficulty in shopping or cooking, and poor quality meals.
|Impaired digestion &/or absorption||This can result from conditions that affect the digestive system.|
|Altered requirements||Changes to metabolic demands can be caused by illness, surgery and organ dysfunction.|
|Excess nutrient losses|| Losses from the gastrointestinal can occur because of symptoms such as vomiting or diarrhea, as well as fistulae and stomas. There can also be losses from drains, including nasogastric tubes.
Other losses: Conditions such as burns can be associated with losses such as skin exudates.
Weight loss issues related to specific diseases include:
- As chronic obstructive pulmonary disease (COPD) advances, about 35% of patients experience severe weight loss called pulmonary cachexia, including diminished muscle mass. Around 25% experience moderate to severe weight loss, and most others have some weight loss. Greater weight loss is associated with poorer prognosis. Theories about contributing factors include appetite loss related to reduced activity, additional energy required for breathing, and the difficulty of eating with dyspnea (labored breathing).
- Cancer, a very common and sometimes fatal cause of unexplained (idiopathic) weight loss. About one-third of unintentional weight loss cases are secondary to malignancy. Cancers to suspect in patients with unexplained weight loss include gastrointestinal, prostate, hepatobilary (hepatocellular carcinoma, pancreatic cancer), ovarian, hematologic or lung malignancies.
- People with HIV often experience weight loss, and it is associated with poorer outcomes. Wasting syndrome is an AIDS-defining condition.
- Gastrointestinal disorders are another common cause of unexplained weight loss – in fact they are the most common non-cancerous cause of idiopathic weight loss. 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.
- Infection. Some infectious diseases can cause weight loss. Fungal illnesses, endocarditis, many parasitic diseases, AIDS, 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
- Neurologic disease, including dementia
- Oral, taste or dental problems (including infections) can reduce nutrient intake leading to weight loss.
Many patients will be in pain and have a loss of appetite after surgery. Part of the body's response to surgery is to direct energy to wound healing, which increases the body's overall energy requirements. Surgery affects nutritional status indirectly, particularly during the recovery period, as it can interfere with wound healing and other aspects of recovery. Surgery directly affects nutritional status if a procedure permanently alters the digestive system. Enteral nutrition (tube feeding) is often needed. However a policy of 'nil by mouth' for all gastrointestinal surgery has not been shown to benefit, with some suggestion it might hinder recovery.
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.
Social conditions such as poverty, social isolation and inability to get or prepare preferred foods can cause unintentional weight loss, and this may be particularly common in older people. Nutrient intake can also be affected by culture, family and belief systems. Ill-fitting dentures and other dental or oral health problems can also affect adequacy of nutrition.
Weight loss in individuals who are overweight or obese can reduce health risks, increase fitness, and may delay the onset of diabetes. It could reduce pain and increase movement in people with osteoarthritis of the knee. Weight loss can lead to a reduction in hypertension (high blood pressure), however whether this reduces hypertension-related harm is unclear.
Weight loss occurs when the body is expending more energy in work and metabolism than it is absorbing from food or other nutrients. It will then use stored reserves from fat or muscle, gradually leading to weight loss.
For athletes seeking to improve performance or to meet required weight classification for participation in a sport, it is not uncommon to seek additional weight loss even if they are already at their ideal body weight. Others may be driven to lose weight to achieve an appearance they consider more attractive. Being underweight is associated with health risks such as difficulty fighting off infection, osteoporosis, decreased muscle strength, trouble regulating body temperature and even increased risk of death.
Low-calorie diets are also referred to as balanced percentage diets. Due to their minimal detrimental effects, these types of diets are most commonly recommended by nutritionists. In addition to restricting calorie intake, a balanced diet also regulates macronutrient consumption. From the total number of allotted daily calories, it is recommended that 55% should come from carbohydrates, 15% from protein, and 30% from fats with no more than 10% of total fat coming from saturated forms. For instance, a recommended 1,200 calorie diet would supply about 660 calories from carbohydrates, 180 from protein, and 360 from fat. Some studies suggest that increased consumption of protein can help ease hunger pains associated with reduced caloric intake by increasing the feeling of satiety. Calorie restriction in this way has many long-term benefits. After reaching the desired body weight, the calories consumed per day may be increased gradually, without exceeding 2,000 net (i.e. derived by subtracting calories burned by physical activity from calories consumed). Combined with increased physical activity, low-calorie diets are thought to be most effective long-term, unlike crash diets, which can achieve short-term results, at best. Physical activity could greatly enhance the efficiency of a diet. The healthiest weight loss regimen, therefore, is one that consists of a balanced diet and moderate physical activity.
Weight gain has been associated with excessive consumption of fats, (added) sugars, refined carbohydrates in general, and alcohol consumption. Depression, stress or boredom may also contribute to weight increase, 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.
According to 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. According to the U.S. Food and Drug Administration (FDA), healthy individuals seeking to maintain their weight should consume 2,000 calories (8.4 MJ) per day.
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. The World Health Organization recommended that people combine a reduction of processed foods high in saturated fats, sugar and salt and caloric content of the diet with an increase in physical activity.
An increase in fiber intake is also recommended for regulating bowel movements.
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.
Dietary supplements, though widely used, are not considered a healthy option for weight loss. Many are available, but very few are effective in the long term.
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. In 1996 a study found that cognitive-behavioral therapy (CBT) was more effective for weight reduction if reinforced with hypnosis. Acceptance and Commitment Therapy ACT, a mindfulness approach to weight loss, has also in the last few years been demonstrating its usefulness.
Permanent weight loss
In order for weight loss to be permanent, changes in diet and lifestyle must be permanent as well. Short-term dieting has not been shown to produce either long term weight loss or better health, and may even be counterproductive.
Weight loss industry
There is a substantial market for products which promise 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.
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.
A 1-kg loss of body weight has been associated with an approximate 1-mm Hg drop in blood pressure.
- National Cancer Institute (November 2011). "Nutrition in cancer care (PDQ)". Physician Data Query. National Cancer Institute. Retrieved 3 July 2013.
- Huffman, GB (Feb 15, 2002). "Evaluating and treating unintentional weight loss in the elderly". American family physician. 65 (4): 640–50. PMID 11871682.
- Payne, C; Wiffen, PJ; Martin, S (Jan 18, 2012). Payne, Cathy, ed. "Interventions for fatigue and weight loss in adults with advanced progressive illness". The Cochrane database of systematic reviews. 1: CD008427. doi:10.1002/14651858.CD008427.pub2. PMID 22258985.
- Institute of Medicine (U.S.). Committee on Nutrition Services for Medicare Beneficiaries. The role of nutrition in maintaining health in the nation's elderly: evaluating coverage of nutrition services for the Medicare population. p. 67. ISBN 978-0-309-06846-8.
- National Collaborating Centre for Acute Care (UK) (February 2006). "Nutrition Support for Adults: Oral Nutrition Support, Enteral Tube Feeding and Parenteral Nutrition". NICE Clinical Guidelines, No. 32. National Collaborating Centre for Acute Care (UK).
- Yaxley, A; Miller, MD; Fraser, RJ; Cobiac, L (February 2012). "Pharmacological interventions for geriatric cachexia: a narrative review of the literature.". The journal of nutrition, health & aging. 16 (2): 148–54. doi:10.1007/s12603-011-0083-8. PMID 22323350.
- Itoh, M; Tsuji, T; Nemoto, K; Nakamura, H; Aoshiba, K (Apr 18, 2013). "Undernutrition in patients with COPD and its treatment". Nutrients. 5 (4): 1316–35. doi:10.3390/nu5041316. PMC 3705350. PMID 23598440.
- Mangili A, Murman DH, Zampini AM, Wanke CA; Murman; Zampini; Wanke (2006). "Nutrition and HIV infection: review of weight loss and wasting in the era of highly active antiretroviral therapy from the nutrition for healthy living cohort". Clin. Infect. Dis. 42 (6): 836–42. doi:10.1086/500398. PMID 16477562.
- Nygaard, B (Jul 19, 2010). "Hyperthyroidism (primary)". Clinical evidence. 2010: 0611. PMC 3275323. PMID 21418670.
- National Collaborating Centre for Chronic Conditions (UK). "Type 1 diabetes in adults: National clinical guideline for diagnosis and management in primary and secondary care". NICE Clinical Guidelines, No. 15.1. Royal College of Physicians UK. Retrieved 3 July 2013.
- Mangili, A; Murman, DH; Zampini, AM; Wanke, CA (Mar 15, 2006). "Nutrition and HIV infection: review of weight loss and wasting in the era of highly active antiretroviral therapy from the nutrition for healthy living cohort". Clinical Infectious Diseases. 42 (6): 836–42. doi:10.1086/500398. PMID 16477562.
- Massompoor SM (April 2004). "Unintentional weight loss". Shiraz E-Medical Journal. 5 (2).
- Andersen, HK; Lewis, SJ; Thomas, S (Oct 18, 2006). Andersen, Henning Keinke, ed. "Early enteral nutrition within 24h of colorectal surgery versus later commencement of feeding for postoperative complications". The Cochrane Database of Systematic Reviews (4): CD004080. doi:10.1002/14651858.CD004080.pub2. PMID 17054196. Lay summary.
- Burden, S; Todd, C; Hill, J; Lal, S (2012). Burden, Sorrel, ed. "Pre‐operative Nutrition Support in Patients Undergoing Gastrointestinal Surgery". The Cochrane Database of Systematic Reviews. 11 (11): CD008879. doi:10.1002/14651858.CD008879.pub2. PMID 23152265. Lay summary.
- Mariotti, KC; Rossato, LG; Fröehlich, PE; Limberger, RP (Nov 2013). "Amphetamine-type medicines: a review of pharmacokinetics, pharmacodynamics, and toxicological aspects". Current clinical pharmacology. 8 (4): 350–7. doi:10.2174/15748847113089990052. PMID 23342978.
- Sarnes, E; Crofford, L; Watson, M; Dennis, G; Kan, H; Bass, D (Oct 2011). "Incidence and US costs of corticosteroid-associated adverse events: a systematic literature review". Clinical therapeutics. 33 (10): 1413–32. doi:10.1016/j.clinthera.2011.09.009. PMID 21999885.
- Serretti, A; Mandelli, L (October 2010). "Antidepressants and body weight: a comprehensive review and meta-analysis". The Journal of Clinical Psychiatry. 71 (10): 1259–72. doi:10.4088/JCP.09r05346blu. PMID 21062615.
- Alibhai, SM; Greenwood, C; Payette, H (Mar 15, 2005). "An approach to the management of unintentional weight loss in elderly people". Canadian Medical Association Journal. 172 (6): 773–80. doi:10.1503/cmaj.1031527. PMC 552892. PMID 15767612.
- LeBlanc, E; O'Connor, E; Whitlock, EP (October 2011). "Screening for and management of obesity and overweight in adults". Evidence Syntheses, No. 89. U.S. Agency for Healthcare Research and Quality (AHRQ). Retrieved 27 June 2013.
- Institute for Quality and Efficiency in Health Care. "Health benefits of losing weight". Fact sheet, Informed Health Online. Institute for Quality and Efficiency in Health Care. Retrieved 27 June 2013.
- "Being underweight poses health risks". Mayo Clinic. Archived from the original on 4 March 2007. Retrieved 13 January 2007.
- "High-Protein Diet for Weight Loss". WebMD.
- Nedeltcheva, AV; Kilkus, JM; Imperial, J; Schoeller, DA; Penev, PD (2010). "Insufficient sleep undermines dietary efforts to reduce adiposity". Annals of Internal Medicine. 153 (7): 435–41. doi:10.1059/0003-4819-153-7-201010050-00006 (inactive 2015-01-01). PMC 2951287. PMID 20921542.
- Harmon, Katherine (4 October 2010). "Sleep might help dieters shed more fat". Scientific American. Retrieved 20 October 2010.
- Pathak, K.; Soares, M. J.; Calton, E. K.; Zhao, Y.; Hallett, J. (2014-06-01). "Vitamin D supplementation and body weight status: a systematic review and meta-analysis of randomized controlled trials". Obesity Reviews: An Official Journal of the International Association for the Study of Obesity. 15 (6): 528–537. doi:10.1111/obr.12162. ISSN 1467-789X. PMID 24528624.
- Sumithran, Priya; Proietto, Joseph (2013). "The defence of body weight: A physiological basis for weight regain after weight loss". Clinical Science. 124 (4): 231–41. doi:10.1042/CS20120223. PMID 23126426.
- "Executive Summary". Dietary Guidelines 2015-2020. Retrieved 2 May 2016.
- "World Health Organization recommends eating less processed food". BBC News. 3 March 2003.
- "Choosing a safe and successful weight loss program". Weight-control Information Network. National Institute of Diabetes and Digestive and Kidney Diseases. April 2008. Retrieved 2011-01-26.
- Albgomi. "Bariatric Surgery Highlights and Facts". Bariatric Surgery Information Guide. bariatricguide.org. Retrieved 13 June 2013.
- "Gastric bypass risks". Mayo Clinic. 2009-02-09.
- Neumark-Sztainer, Dianne; Sherwood, Nancy E.; French, Simone A.; Jeffery, Robert W. (March 1999). "Weight control behaviors among adult men and women: Cause for concern?". Obesity Research. 7 (2): 179–188. doi:10.1002/j.1550-8528.1999.tb00700.x. PMID 10102255.
- Thomas, Paul R. (January–February 2005). "Dietary Supplements For Weight Loss?". Nutrition Today. 40 (1): 6–12.
- Barabasz, Marianne; Spiegel, David (1989). "Hypnotizability and weight loss in obese subjects". International Journal of Eating Disorders. 8 (3): 335–341. doi:10.1002/1098-108X(198905)8:3<335::AID-EAT2260080309>3.0.CO;2-O.
- Kirsch, I. (June 1996). "Hypnotic enhancement of cognitive-behavioral weight loss treatments–another meta-reanalysis". Journal of Consulting and Clinical Psychology. 64 (3): 517–9. doi:10.1037/0022-006X.64.3.517. PMID 8698945. INIST:3143031.
- Andersen, M. S. (1985). "Hypnotizability as a factor in the hypnotic treatment of obesity". International Journal of Clinical and Experimental Hypnosis. 33 (2): 150–159. doi:10.1080/00207148508406645. PMID 4018924.
- Allison, David B.; Faith, Myles S. (June 1996). "Hypnosis as an adjunct to cognitive-behavioral psychotherapy for obesity: A meta-analytic reappraisal". Journal of Consulting and Clinical Psychology. 64 (3): 513–516. doi:10.1037/0022-006X.64.3.513. PMID 8698944.
- Ruiz, F. J. (2010). "A review of Acceptance and Commitment Therapy (ACT) empirical evidence: Correlational, experimental psychopathology, component and outcome studies". International Journal of Psychology and Psychological Therapy. 10 (1): 125–62.
- Mann, T; Tomiyama, AJ; Westling, E; Lew, AM; Samuels, B; Chatman, J (April 2007). "Medicare's search for effective obesity treatments: diets are not the answer". The American Psychologist. 62 (3): 220–33. doi:10.1037/0003-066x.62.3.220. PMID 17469900.
In sum, there is little support for the notion that diets ["severely restricting one’s calorie intake"] lead to lasting weight loss or health benefits.
- "The facts about weight loss products and programs". DHHS Publication No (FDA) 92-1189. US Food and Drug Administration. 1992. Archived from the original on 26 September 2006. Retrieved 2013-05-14.
- "Profiting From America's Portly Population". PRNewswire (Press release). Reuters. 21 April 2008. Retrieved 2009-01-17.
- "No evidence that popular slimming supplements facilitate weight loss, new research finds". 14 July 2010. Retrieved 2010-07-19.
- Harsha, D. W.; Bray, G. A. (2008). "Weight Loss and Blood Pressure Control (Pro)". Hypertension. 51 (6): 1420–1425. doi:10.1161/HYPERTENSIONAHA.107.094011. ISSN 0194-911X.
|Wikimedia Commons has media related to Weight loss.|
- Weight loss at DMOZ
- Health benefits of losing weight By IQWiG at PubMed Health
- Weight-control Information Network U.S. National Institutes of Health
- Nutrition in cancer care By NCI at PubMed Health
- Unintentional weight loss