Weight loss

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,{{cite web |author1=US Department of Health and Human Services. |title=2015–2020 Dietary Guidelines for Americans - health.gov |url=https://health.gov/dietaryguidelines/2015/ |website=health.gov |publisher=Skyhorse Publishing Inc. |access-date=30 September 2019 |date=2017}}{{cite journal |last1=Arnett |first1=Donna K. |last2=Blumenthal |first2=Roger S. |last3=Albert |first3=Michelle A. |last4=Buroker |first4=Andrew B. |last5=Goldberger |first5=Zachary D. |last6=Hahn |first6=Ellen J. |last7=Himmelfarb |first7=Cheryl D. |last8=Khera |first8=Amit |last9=Lloyd-Jones |first9=Donald |last10=McEvoy |first10=J. William |last11=Michos |first11=Erin D. |last12=Miedema |first12=Michael D. |last13=Muñoz |first13=Daniel |last14=Smith |first14=Sidney C. |last15=Virani |first15=Salim S. |last16=Williams |first16=Kim A. |last17=Yeboah |first17=Joseph |last18=Ziaeian |first18=Boback |title=2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease |journal=Circulation |volume=140 |issue=11 |pages=e596–e646 |date=17 March 2019 |doi=10.1161/CIR.0000000000000678 |pmid=30879355 |pmc=7734661 |doi-access=free }} and there is substantial evidence this can prevent progression from prediabetes to type 2 diabetes with a 7–10% weight loss and manage cardiometabolic health for diabetic people with a 5–15% weight loss.{{cite journal |last1=Evert |first1=Alison B. |last2=Dennison |first2=Michelle |last3=Gardner |first3=Christopher D. |last4=Garvey |first4=W. Timothy |author-link4=W. Timothy Garvey |last5=Lau |first5=Ka Hei Karen |last6=MacLeod |first6=Janice |last7=Mitri |first7=Joanna |last8=Pereira |first8=Raquel F. |last9=Rawlings |first9=Kelly |last10=Robinson |first10=Shamera |last11=Saslow |first11=Laura |last12=Uelmen |first12=Sacha |last13=Urbanski |first13=Patricia B. |last14=Yancy |first14=William S. |date=May 2019 |title=Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report |journal=Diabetes Care |type=Professional society guidelines |volume=42 |issue=5 |pages=731–754 |doi=10.2337/dci19-0014 |pmc=7011201 |pmid=31000505}}

Weight loss in individuals who are overweight or obese can reduce health risks, increase fitness,{{cite web|last=Institute for Quality and Efficiency in Health Care|title=Health benefits of losing weight|url=https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0004993/|work=Fact sheet, Informed Health Online|date=8 March 2012 |publisher=Institute for Quality and Efficiency in Health Care|access-date=27 June 2013}} and may delay the onset of diabetes.{{cite journal|last=LeBlanc|first=E |title=Screening for and management of obesity and overweight in adults |url=https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0016399/ |journal=Evidence Syntheses, No. 89 |publisher=U.S. Agency for Healthcare Research and Quality (AHRQ) |access-date=27 June 2013 |author2=O'Connor, E |author3=Whitlock, EP |date=October 2011 |pmid=22049569 }} 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.{{Failed verification|date=May 2016}} Weight loss is achieved by adopting a lifestyle in which fewer calories are consumed than are expended.{{cite web |publisher=National Health Service |title=Health Weight – Understanding Calories |url=https://www.nhs.uk/live-well/healthy-weight/understanding-calories/ |date=19 August 2016}} Depression, stress or boredom may contribute to unwanted weight gain or loss depending on the individual,{{Cite web|url=https://www.psychologytoday.com/us/blog/the-antidepressant-diet/201708/moods-overeating-good-bad-and-bored|title=Moods for Overeating: Good, Bad, and Bored|website=Psychology Today|language=en-US|access-date=2018-10-17}}{{cite journal |last1=Simmons |first1=W. Kyle |last2=Burrows |first2=Kaiping |last3=Avery |first3=Jason A. |last4=Kerr |first4=Kara L. |last5=Bodurka |first5=Jerzy |last6=Savage |first6=Cary R. |last7=Drevets |first7=Wayne C. |title=Depression-Related Increases and Decreases in Appetite: Dissociable Patterns of Aberrant Activity in Reward and Interoceptive Neurocircuitry |journal=American Journal of Psychiatry |date=April 2016 |volume=173 |issue=4 |pages=418–428 |doi=10.1176/appi.ajp.2015.15020162 |pmid=26806872 |pmc=4818200 }} 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.{{Cite journal |last1=Nedeltcheva |first1=AV |last2=Kilkus |first2=JM |last3=Imperial |first3=J |last4=Schoeller |first4=DA |last5=Penev |first5=PD |title=Insufficient sleep undermines dietary efforts to reduce adiposity |journal=Annals of Internal Medicine |volume=153 |issue=7 |pages=435–41 |year=2010 |pmid=20921542 |pmc=2951287 |doi=10.7326/0003-4819-153-7-201010050-00006 }}{{cite web |author=Harmon, Katherine |url=https://blogs.scientificamerican.com/observations/sleep-might-help-dieters-shed-more-fat/ |title=Sleep might help dieters shed more fat |work=Scientific American |date=4 October 2010 |access-date=20 October 2010}} Though hypothesized that supplementation of vitamin D may help, studies do not support this.{{Cite journal|last1=Pathak|first1=K.|last2=Soares|first2=M. J.|last3=Calton|first3=E. K.|last4=Zhao|first4=Y.|last5=Hallett|first5=J.|date=2014-06-01|title=Vitamin D supplementation and body weight status: a systematic review and meta-analysis of randomized controlled trials|pmid=24528624|journal=Obesity Reviews|volume=15|issue=6|pages=528–37|doi=10.1111/obr.12162|s2cid=8660739|issn=1467-789X}} The majority of dieters regain weight over the long term.{{cite journal |doi=10.1042/CS20120223 |title=The defence of body weight: A physiological basis for weight regain after weight loss |year=2013 |last1=Sumithran |first1=Priya |last2=Proietto |first2=Joseph |journal=Clinical Science |volume=124 |issue=4 |pages=231–41 |pmid=23126426}} 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.{{cite web |url=http://health.gov/dietaryguidelines/2015/guidelines/executive-summary/ |title=Executive Summary |work=Dietary Guidelines 2015–2020 |access-date=2 May 2016 }}

For weight loss to be permanent, changes in diet and lifestyle must be permanent as well.{{cite book |last1=Hart |first1=Katherine |editor1-last=Hankey |editor1-first=Catherine |title=Advanced nutrition and dietetics in obesity |date=2018 |publisher=Wiley |isbn=9780470670767 |pages=177–182 |language=en |chapter=4.6 Fad diets and fasting for weight loss in obesity.}}{{Cite book|url=https://books.google.com/books?id=ky5ADwAAQBAJ|title=Advanced Nutrition and Dietetics in Obesity|last=Hankey|first=Catherine|date=2017-11-23|publisher=John Wiley & Sons|isbn=9781118857977|pages=179–181|language=en}}{{cite web|url=https://www.bda.uk.com/foodfacts/faddiets.pdf|title=Fact Sheet—Fad diets|year=2014|publisher=British Dietetic Association|access-date=12 December 2015|quote=Fad-diets can be tempting as they offer a quick-fix to a long-term problem.}} 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.{{Cite journal|last=The Look AHEAD Research Group|date=2014|title=Eight-year weight losses with an intensive lifestyle intervention: The look AHEAD study: 8-Year Weight Losses in Look AHEAD|journal=Obesity|language=en|volume=22|issue=1|pages=5–13|doi=10.1002/oby.20662|pmc=3904491|pmid=24307184}} Meal replacements, orlistat, a very-low-calorie diet, and primary care intensive medical interventions can also support meaningful weight loss.{{cite journal |last1=Thom |first1=G |last2=Lean |first2=M |title=Is There an Optimal Diet for Weight Management and Metabolic Health? |journal=Gastroenterology |date=May 2017 |volume=152 |issue=7 |pages=1739–1751 |doi=10.1053/j.gastro.2017.01.056 |pmid=28214525|url=http://eprints.gla.ac.uk/137779/7/137779.pdf }}{{Cite journal |last1=Katzmarzyk |first1=Peter T. |last2=Martin |first2=Corby K. |last3=Newton |first3=Robert L. |last4=Apolzan |first4=John W. |last5=Arnold |first5=Connie L. |last6=Davis |first6=Terry C. |last7=Price-Haywood |first7=Eboni G. |last8=Denstel |first8=Kara D. |last9=Mire |first9=Emily F. |last10=Thethi |first10=Tina K. |last11=Brantley |first11=Phillip J. |last12=Johnson |first12=William D. |last13=Fonseca |first13=Vivian |last14=Gugel |first14=Jonathan |last15=Kennedy |first15=Kathleen B. |date=2020-09-03 |title=Weight Loss in Underserved Patients — A Cluster-Randomized Trial |journal=New England Journal of Medicine |language=en |volume=383 |issue=10 |pages=909–918 |doi=10.1056/NEJMoa2007448 |issn=0028-4793 |pmc=7493523 |pmid=32877581}}

{{See also|Management of obesity}}

File:Obesity Med2008.JPG (Xenical), a commonly used anti-obesity medication, and sibutramine (Meridia), a withdrawn medication due to cardiovascular side effects]]

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.{{cite journal | last1=Varkevisser | first1=R. D. M. | last2=van Stralen | first2=M. M. | last3=Kroeze | first3=W. | last4=Ket | first4=J. C. F. | last5=Steenhuis | first5=I. H. M. | title=Determinants of weight loss maintenance: a systematic review | journal=Obesity Reviews| volume=20 | issue=2 | date=2018-10-16 | issn=1467-7881 | pmid=30324651 | pmc=7416131 | doi=10.1111/obr.12772 | pages=171–211}} The World Health Organization recommends that people combine a reduction of processed foods high in saturated fats, sugar and salt,{{cite news |url=http://news.bbc.co.uk/2/hi/health/2814253.stm |title=World Health Organization recommends eating less processed food|work=BBC News| date=3 March 2003}} and reduced caloric intake with an increase in physical activity.{{cite web |url=https://www.niddk.nih.gov/health-information/weight-management/choosing-a-safe-successful-weight-loss-program |title=Choosing a safe and successful weight loss program |work=Weight-control Information Network |publisher=National Institute of Diabetes and Digestive and Kidney Diseases |date=July 2017 |access-date=2020-07-17}} Both long-term exercise programs and anti-obesity medications reduce abdominal fat volume.{{cite journal|display-authors=3| last1=Rao | first1=S | last2=Pandey | first2=A | last3=Garg | first3=S | last4=Park | first4=B | last5=Mayo | first5=H | last6=Després | first6=JP | last7=Kumbhani | first7=D | last8=de Lemos | first8=JA | last9=Neeland | first9=IJ | title=Effect of Exercise and Pharmacological Interventions on Visceral Adiposity: A Systematic Review and Meta-analysis of Long-term Randomized Controlled Trials. | journal=Mayo Clinic Proceedings | volume=94 | issue=2 | year=2019 | pages=211–224 | pmid=30711119 | pmc=6410710| doi=10.1016/j.mayocp.2018.09.019 }}

Self-monitoring of diet, exercise, and weight are beneficial strategies for weight loss,{{Cite journal|last1=Burke|first1=Lora E.|last2=Wang|first2=Jing|last3=Sevick|first3=Mary Ann|date=2011|title=Self-Monitoring in Weight Loss: A Systematic Review of the Literature|journal=Journal of the American Dietetic Association|language=en|volume=111|issue=1|pages=92–102|doi=10.1016/j.jada.2010.10.008|pmc=3268700|pmid=21185970}}{{Cite journal|last1=Steinberg|first1=Dori M.|last2=Tate|first2=Deborah F.|last3=Bennett|first3=Gary G.|last4=Ennett|first4=Susan|last5=Samuel-Hodge|first5=Carmen|last6=Ward|first6=Dianne S.|date=2013|title=The efficacy of a daily self-weighing weight loss intervention using smart scales and e-mail: Daily Self-Weighing Weight Loss Intervention|journal=Obesity|language=en|volume=21|issue=9|pages=1789–97|doi=10.1002/oby.20396|pmc=3788086|pmid=23512320}} particularly early in weight loss programs.{{Cite journal|last1=Krukowski|first1=Rebecca A.|last2=Harvey-Berino|first2=Jean|last3=Bursac|first3=Zoran|last4=Ashikaga|first4=Taka|last5=West|first5=Delia Smith|date=2013|title=Patterns of success: Online self-monitoring in a web-based behavioral weight control program.|journal=Health Psychology|language=en|volume=32|issue=2|pages=164–170|doi=10.1037/a0028135|issn=1930-7810|pmc=4993110|pmid=22545978}} 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.{{Cite journal|last1=Harvey|first1=Jean|last2=Krukowski|first2=Rebecca|last3=Priest|first3=Jeff|last4=West|first4=Delia|date=2019|title=Log Often, Lose More: Electronic Dietary Self-Monitoring for Weight Loss: Log Often, Lose More|journal=Obesity|language=en|volume=27|issue=3|pages=380–384|doi=10.1002/oby.22382|pmc=6647027|pmid=30801989}}

Permanent weight loss depends on maintaining a negative energy balance and not the type of macronutrients (such as carbohydrate) consumed.{{cite journal |last1=Bayer |first1=Sandra |last2=Holzapfel |first2=Christina |title=Carbohydrate intake – current knowledge on weight management |journal=Current Opinion in Clinical Nutrition & Metabolic Care |date=July 2022 |volume=25 |issue=4 |pages=265–270 |doi=10.1097/MCO.0000000000000840 |pmid=35762163 |s2cid=250078610 |issn=1363-1950}} 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.{{cite journal |last1=Magkos |first1=Faidon |title=Protein-Rich Diets for Weight Loss Maintenance |journal=Current Obesity Reports |date=2020 |volume=9 |issue=3 |pages=213–218 |doi=10.1007/s13679-020-00391-0|pmid=32542589 |s2cid=219691446 |doi-access=free }}

Increasing water intake can reduce weight by increasing thermogenesis, by reducing food intake, and by increasing fat oxidation.{{cite journal | vauthors=Dazıroğlu ME, Tek NA | title=Water Consumption: Effect on Energy Expenditure and Body Weight Management | journal=Current Obesity Reports | volume=12 | issue=2 | pages=99–107 | year=2023 | doi= 10.1007/s13679-023-00501-8 | pmid=37036559}} Persons dieting for weight loss have demonstrated the weight-reducing effects of increased water consumption.{{cite journal | vauthors=Muckelbauer R, Sarganas G, Grüneis A, Müller-Nordhorn J | title=Association between water consumption and body weight outcomes: a systematic review | journal=The American Journal of Clinical Nutrition | volume=98 | issue=2| pages=282–299 | year=2013 | doi= 10.3945/ajcn.112.055061 | pmid=23803882| doi-access=free }} Among adults in the U.S. there is a significant association between inadequate hydration and obesity.{{cite journal | vauthors = Chang T, Ravi N, Davis MM | title=Inadequate Hydration, BMI, and Obesity Among US Adults: NHANES 2009–2012 | journal=Annals of Family Medicine | volume=14 | issue=4 | pages=320–324 | year=2016 | doi= 10.1370/afm.1951 | pmc=4940461 | pmid=27401419}}

{{main|Anti-obesity medication}}

Other methods of weight loss include use of anti-obesity drugs that decrease appetite, block fat absorption, or reduce stomach volume.{{citation needed|date=September 2022}} Obesity has been resistant to drug-based therapies, with a 2021 review stating that existing medications are "often delivering insufficient efficacy and dubious safety".{{cite journal |last1=Müller |first1=Timo D. |last2=Blüher |first2=Matthias |last3=Tschöp |first3=Matthias H. |last4=DiMarchi |first4=Richard D. |title=Anti-obesity drug discovery: advances and challenges |journal=Nature Reviews Drug Discovery |date=2022 |volume=21 |issue=3 |pages=201–223 |doi=10.1038/s41573-021-00337-8 |pmid=34815532 |pmc=8609996 |language=en |issn=1474-1784}} Semaglutide has also become popular recently as an aid in weight loss.{{Cite web |last=Mazaheri |first=Dr. Mehdi K. |title=How to Stop Rebound Weight Gain After Taking Semaglutide |url=https://drmazaheri.com/how-to-stop-rebound-weight-gain-after-taking-semaglutide/ |access-date=September 19, 2023 |website=Dr. Mazaheri|date=19 September 2023 }} It is particularly beneficial for those with type 2 diabetes and obesity.

Bariatric surgery may be indicated in cases of severe obesity. Two common bariatric surgical procedures are gastric bypass and gastric banding.{{cite web|last=Albgomi|title=Bariatric Surgery Highlights and Facts|url=http://www.bariatricguide.org/what-is-bariatric-surgery/|work=Bariatric Surgery Information Guide|publisher=bariatricguide.org|access-date=13 June 2013}} 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{{cite web |url=http://www.mayoclinic.com/health/gastric-bypass/my00825/dsection=risks|title=Gastric bypass risks|publisher=Mayo Clinic|date=2009-02-09}} that should be considered in consultation with a physician.

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.{{cite web |url=http://www.cfsan.fda.gov/~dms/wgtloss.html |publisher=US Food and Drug Administration |title=The facts about weight loss products and programs |work=DHHS Publication No (FDA) 92-1189 |year=1992 |access-date=2013-05-14 |url-status=dead |archive-url=https://web.archive.org/web/20060926035920/http://www.cfsan.fda.gov/~dms/wgtloss.html |archive-date=26 September 2006 }} Dietary supplements, though widely used, are not considered a healthy option for weight loss, and have no clinical evidence of efficacy.{{Cite journal |title=Weight control behaviors among adult men and women: Cause for concern? |last1=Neumark-Sztainer |first1=Dianne |last2=Sherwood |first2=Nancy E. |last3=French |first3=Simone A. |last4=Jeffery |first4=Robert W. |journal=Obesity Research |volume=7 |issue=2 |pages=179–88 |date=March 1999 |doi=10.1002/j.1550-8528.1999.tb00700.x |pmid= 10102255|doi-access=free }} Herbal products have not been shown to be effective.{{Cite journal|last1=Maunder|first1=Alison|last2=Bessell|first2=Erica|last3=Lauche|first3=Romy|last4=Adams|first4=Jon|last5=Sainsbury|first5=Amanda|last6=Fuller|first6=Nicholas R.|date=2020-01-27|title=Effectiveness of herbal medicines for weight loss: A systematic review and meta-analysis of randomized controlled trials|journal=Diabetes, Obesity & Metabolism|volume=22|issue=6|pages=891–903|doi=10.1111/dom.13973|issn=1463-1326|pmid=31984610|doi-access=free}}

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.{{cite press release |url=https://www.reuters.com/article/pressRelease/idUS107630+21-Apr-2008+PRN20080421 |title=Profiting From America's Portly Population |work=Reuters |publisher=PR Newswire |date=21 April 2008 |access-date=2009-01-17 |url-status=dead |archive-url=https://web.archive.org/web/20090311065323/https://www.reuters.com/article/pressRelease/idUS107630+21-Apr-2008+PRN20080421 |archive-date=2009-03-11}}

In Western Europe, sales of weight-loss products, excluding prescription medications, topped €1,25 billion (£900 million/$1.4 billion) in 2009.{{cite web |url=https://www.sciencedaily.com/releases/2010/07/100712103445.htm |title=No evidence that popular slimming supplements facilitate weight loss, new research finds |date=14 July 2010 |access-date=2010-07-19}}

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.{{cite journal |last1=Thom |first1=G |last2=Lean |first2=M |title=Is There an Optimal Diet for Weight Management and Metabolic Health? |journal=Gastroenterology |date=May 2017 |volume=152 |issue=7 |pages=1739–1751 |doi=10.1053/j.gastro.2017.01.056 |pmid=28214525 |type=Review|url=http://eprints.gla.ac.uk/137779/7/137779.pdf }}{{cite journal |last1=Wadden |first1=Thomas A. |last2=Webb |first2=Victoria L. |last3=Moran |first3=Caroline H. |last4=Bailer |first4=Brooke A. |title=Lifestyle Modification for Obesity |journal=Circulation |date=6 March 2012 |volume=125 |issue=9 |pages=1157–1170 |doi=10.1161/CIRCULATIONAHA.111.039453 |pmid=22392863 |pmc=3313649 |type=Narrative review}}{{cite journal |last1=Atallah |first1=R. |last2=Filion |first2=K. B. |last3=Wakil |first3=S. M. |last4=Genest |first4=J. |last5=Joseph |first5=L. |last6=Poirier |first6=P. |last7=Rinfret |first7=S. |last8=Schiffrin |first8=E. L. |last9=Eisenberg |first9=M. J. |title=Long-Term Effects of 4 Popular Diets on Weight Loss and Cardiovascular Risk Factors: A Systematic Review of Randomized Controlled Trials |journal=Circulation: Cardiovascular Quality and Outcomes |date=11 November 2014 |volume=7 |issue=6 |pages=815–827 |doi=10.1161/CIRCOUTCOMES.113.000723 |pmid=25387778 |type=Systematic review of RCTs|doi-access=free }}{{cite book |last1=Avery |first1=Amanda |editor1-last=Hankey |editor1-first=Catherine |title=Advanced nutrition and dietetics in obesity |date=2018 |publisher=Wiley |isbn=9780470670767 |pages=177–182 |language=en |chapter=4.7 Commercial weight management organisations for weight loss in obesity.}}{{cite journal |last1=Tsai |first1=AG |last2=Wadden |first2=TA |title=Systematic review: an evaluation of major commercial weight loss programs in the United States. |journal=Annals of Internal Medicine |date=4 January 2005 |volume=142 |issue=1 |pages=56–66 |doi=10.7326/0003-4819-142-1-200501040-00012 |pmid=15630109 |s2cid=2589699 |type=Systematic review}}{{cite book |last1=Allan |first1=Karen |editor1-last=Hankey |editor1-first=Catherine |title=Advanced nutrition and dietetics in obesity |date=2018 |publisher=Wiley |isbn=9780470670767 |pages=164–168 |language=en |chapter=4.4 Group-based interventions for weight loss in obesity.}} Commercial diets result in modest weight loss in the long term, with similar results regardless of the brand,{{cite journal |last1=Vakil |first1=RM |last2=Doshi |first2=RS |last3=Mehta |first3=AK |last4=Chaudhry |first4=ZW |last5=Jacobs |first5=DK |last6=Lee |first6=CJ |last7=Bleich |first7=SN |last8=Clark |first8=JM |last9=Gudzune |first9=KA |title=Direct comparisons of commercial weight-loss programs on weight, waist circumference, and blood pressure: a systematic review. |journal=BMC Public Health |date=1 June 2016 |volume=16 |pages=460 |doi=10.1186/s12889-016-3112-z |pmid=27246464 |pmc=4888663 |type=Systematic review |doi-access=free }} and similarly to non-commercial diets and standard care.{{cite journal |last1=Jensen |first1=MD |last2=Ryan |first2=DH |last3=Apovian |first3=CM |last4=Ard |first4=JD |last5=Comuzzie |first5=AG |last6=Donato |first6=KA |last7=Hu |first7=FB |last8=Hubbard |first8=VS |last9=Jakicic |first9=JM |last10=Kushner |first10=RF |last11=Loria |first11=CM |last12=Millen |first12=BE |last13=Nonas |first13=CA |last14=Pi-Sunyer |first14=FX |last15=Stevens |first15=J |last16=Stevens |first16=VJ |last17=Wadden |first17=TA |last18=Wolfe |first18=BM |last19=Yanovski |first19=SZ |last20=Jordan |first20=HS |last21=Kendall |first21=KA |last22=Lux |first22=LJ |last23=Mentor-Marcel |first23=R |last24=Morgan |first24=LC |last25=Trisolini |first25=MG |last26=Wnek |first26=J |last27=Anderson |first27=JL |last28=Halperin |first28=JL |last29=Albert |first29=NM |last30=Bozkurt |first30=B |last31=Brindis |first31=RG |last32=Curtis |first32=LH |last33=DeMets |first33=D |last34=Hochman |first34=JS |last35=Kovacs |first35=RJ |last36=Ohman |first36=EM |last37=Pressler |first37=SJ |last38=Sellke |first38=FW |last39=Shen |first39=WK |last40=Smith SC |first40=Jr |last41=Tomaselli |first41=GF |last42=American College of Cardiology/American Heart Association Task Force on Practice |first42=Guidelines. |last43=Obesity |first43=Society. |title=2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and The Obesity Society. |journal=Circulation |date=24 June 2014 |volume=129 |issue=25 Suppl 2 |pages=S102-38 |doi=10.1161/01.cir.0000437739.71477.ee |pmid=24222017|pmc=5819889 |type=Professional society guideline}} Comprehensive diet programs, providing counseling and targets for calorie intake, are more efficient than dieting without guidance ("self-help"),{{cite journal |last1=Kernan |first1=Walter N. |last2=Inzucchi |first2=Silvio E. |last3=Sawan |first3=Carla |last4=Macko |first4=Richard F. |last5=Furie |first5=Karen L. |title=Obesity – A Stubbornly Obvious Target for Stroke Prevention |journal=Stroke |date=January 2013 |volume=44 |issue=1 |pages=278–286 |doi=10.1161/STROKEAHA.111.639922 |pmid=23111440 |type=Review|doi-access=free }}{{cite journal|last1=Gudzune|first1=KA|last2=Doshi|first2=RS|last3=Mehta|first3=AK|last4=Chaudhry|first4=ZW|last5=Jacobs|first5=DK|last6=Vakil|first6=RM|last7=Lee|first7=CJ|last8=Bleich|first8=SN|last9=Clark|first9=JM|title=Efficacy of commercial weight-loss programs: an updated systematic review.|journal=Annals of Internal Medicine|date=7 April 2015|volume=162|issue=7|pages=501–512|pmid=25844997|pmc=4446719|doi=10.7326/M14-2238}} 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.

{{See also|Eating disorder}}

Unintentional weight loss may result from loss of body fats, loss of body fluids, muscle atrophy, or 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{{cite journal|last=National Cancer Institute|title=Nutrition in cancer care (PDQ)|url=https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0032688/|journal=Physician Data Query|publisher=National Cancer Institute|access-date=3 July 2013|date=November 2011|pmid=26389293 }} or 5% in the last month.{{cite book|url=https://archive.org/details/roleofnutritioni0000inst |url-access=registration |page=[https://archive.org/details/roleofnutritioni0000inst/page/67 67]|title=The role of nutrition in maintaining health in the nation's elderly: evaluating coverage of nutrition services for the Medicare population |publisher=National Academies Press |author=Institute of Medicine (U.S.). Committee on Nutrition Services for Medicare Beneficiaries|isbn=978-0-309-06846-8|date=2000-06-09}} 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.{{cite journal|last=Yaxley|first=A|author2=Miller, MD |author3=Fraser, RJ |author4= Cobiac, L |title=Pharmacological interventions for geriatric cachexia: a narrative review of the literature.|journal=The Journal of Nutrition, Health & Aging|date=February 2012|volume=16|issue=2|pages=148–54|pmid=22323350|url=https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0052255/|doi=10.1007/s12603-011-0083-8|s2cid=30473679|doi-access=free}}

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.{{cite journal|last=Huffman|first=GB|title=Evaluating and treating unintentional weight loss in the elderly|journal=American Family Physician|date=15 February 2002|volume=65|issue=4|pages=640–50|pmid=11871682}}{{cite journal|last=Itoh|first=M|author2=Tsuji, T |author3=Nemoto, K |author4=Nakamura, H |author5= Aoshiba, K |title=Undernutrition in patients with COPD and its treatment|journal=Nutrients|date=18 April 2013|volume=5|issue=4|pages=1316–35|pmid=23598440|doi=10.3390/nu5041316|pmc=3705350|doi-access=free}}{{cite journal |author=Mangili A, Murman DH, Zampini AM, Wanke CA |title=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 |journal=Clin. Infect. Dis. |volume=42 |issue=6 |pages=836–42 |year=2006 |pmid=16477562 |doi=10.1086/500398|last2=Murman |last3=Zampini |last4=Wanke |doi-access=free }}{{cite journal|last=Nygaard|first=B|title=Hyperthyroidism (primary) |journal=Clinical Evidence|date=19 July 2010|volume=2010|pmid=21418670|pmc=3275323|pages=0611}} 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.{{cite journal|last=Payne|first=C|author2=Wiffen, PJ |author3=Martin, S |title=Interventions for fatigue and weight loss in adults with advanced progressive illness|journal=The Cochrane Database of Systematic Reviews|date=18 January 2012|volume=1|pages=CD008427|pmid=22258985|doi=10.1002/14651858.CD008427.pub2|s2cid=261730608|editor1-last=Payne|editor1-first=Cathy}} {{Retracted|doi=10.1002/14651858.CD008427.pub3|pmid=28387447|intentional=yes}} 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
• menstruation.

Malnutrition can lead to vitamin and other deficiencies and to inactivity, which in turn may pre-dispose to other problems, such as pressure sores. Unintentional weight loss can be the characteristic leading to diagnosis of diseases such as cancer and type 1 diabetes.{{Cite book|last=National Collaborating Centre for Chronic Conditions (UK)|title=Type 1 diabetes in adults: National clinical guideline for diagnosis and management in primary and secondary care |url=https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0016045/ |work=NICE Clinical Guidelines, No. 15.1 |publisher=Royal College of Physicians UK |access-date=3 July 2013|isbn=978-1860162282 |year=2004 }} 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.

Disease-related malnutrition can be considered in four categories:

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, hepatobiliary (hepatocellular carcinoma, pancreatic cancer), ovarian, hematologic or lung malignancies.
• People with HIV often experience weight loss, and it is associated with poorer outcomes.{{cite journal|last=Mangili|first=A|author2=Murman, DH |author3=Zampini, AM |author4= Wanke, CA |title=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 |journal=Clinical Infectious Diseases |date=15 March 2006|volume=42|issue=6|pages=836–42|pmid=16477562|doi=10.1086/500398|doi-access=free}} 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.{{citation needed|date=October 2013}} 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, chronic mesenteric ischemia{{cite journal |last1=Bakhtiar |first1=A |last2=Yousphi |first2=AS |last3=Ghani |first3=AR |last4=Ali |first4=Z |last5=Ullah |first5=W |title=Weight Loss: A Significant Cue To The Diagnosis of Chronic Mesenteric Ischemia. |journal=Cureus |date=7 August 2019 |volume=11 |issue=8 |pages=e5335 |doi=10.7759/cureus.5335 |doi-access=free |pmid=31598442|pmc=6778047 }} 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.

Medical treatment can directly or indirectly cause weight loss, impairing treatment effectiveness and recovery that can lead to further weight loss in a vicious cycle. 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.{{Cite book|last=National Collaborating Centre for Acute Care (UK)|title=Nutrition Support for Adults: Oral Nutrition Support, Enteral Tube Feeding and Parenteral Nutrition|chapter=Malnutrition and the principles of nutrition support |chapter-url=https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0009169/|journal=NICE Clinical Guidelines, No. 32|publisher=National Collaborating Centre for Acute Care (UK)|date=February 2006}} 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 weak evidence suggesting it might hinder recovery.{{Cite journal|last1=Herbert|first1=Georgia|last2=Perry|first2=Rachel|last3=Andersen|first3=Henning Keinke|last4=Atkinson|first4=Charlotte|last5=Penfold|first5=Christopher|last6=Lewis|first6=Stephen J.|last7=Ness|first7=Andrew R.|last8=Thomas|first8=Steven|date=2018|title=Early enteral nutrition within 24 hours of lower gastrointestinal surgery versus later commencement for length of hospital stay and postoperative complications|journal=The Cochrane Database of Systematic Reviews|volume=10|issue=10 |pages=CD004080|doi=10.1002/14651858.CD004080.pub3|issn=1469-493X|pmc=6517065|pmid=30353940}} Early post-operative nutrition is a part of Enhanced Recovery After Surgery protocols.{{Cite journal |last1=Sowerbutts |first1=Anne Marie |last2=Burden |first2=Sorrel |last3=Sremanakova |first3=Jana |last4=French |first4=Chloe |last5=Knight |first5=Stephen R. |last6=Harrison |first6=Ewen M. |date=2024-04-08 |title=Preoperative nutrition therapy in people undergoing gastrointestinal surgery |journal=The Cochrane Database of Systematic Reviews |volume=2024 |issue=4 |pages=CD008879 |doi=10.1002/14651858.CD008879.pub3 |issn=1469-493X |pmc=11001290 |pmid=38588454}} 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.{{cite journal|last=Alibhai|first=SM|author2=Greenwood, C |author3=Payette, H |title=An approach to the management of unintentional weight loss in elderly people |journal=Canadian Medical Association Journal|date=15 March 2005 |volume=172|issue=6|pages=773–80 |pmid=15767612 |doi=10.1503/cmaj.1031527 |pmc=552892 }} 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.

Loss of hope, status or social contact and spiritual distress can cause depression, which may be associated with reduced nutrition, as can fatigue.

Some popular beliefs attached to weight loss have been shown to either have less effect on weight loss than commonly believed or are actively unhealthy. According to Harvard Health, the idea of metabolic rate being the "key to weight" is "part truth and part myth" as while metabolism does affect weight loss, external forces such as diet and exercise have an equal effect.{{Cite news|url=https://www.health.harvard.edu/diet-and-weight-loss/does-metabolism-matter-in-weight-loss|title=Does Metabolism Matter in Weight Loss? |work=Harvard Health|access-date=2018-06-18|language=en-US}} They also commented that the idea of changing one's rate of metabolism is under debate. Diet plans in fitness magazines are also often believed to be effective but may actually be harmful by limiting the daily intake of important calories and nutrients which can be detrimental depending on the person and are even capable of driving individuals away from weight loss.{{Cite book|title=The Gale Encyclopedia of Senior Health|last=Long|first=Jacqueline|publisher=Gale|year=2015|isbn=978-1573027526|location=Detroit, MI}}

{{Further|Obesity#Effects on health}}

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 {{convert|1|kg}} loss of body weight has been associated with an approximate {{convert|1|mmHg}} drop in blood pressure.{{cite journal|last1=Harsha|first1=D. W.|last2=Bray|first2=G. A.|title=Weight Loss and Blood Pressure Control (Pro)|journal=Hypertension|volume=51|issue=6|year=2008|pages=1420–25|issn=0194-911X|doi=10.1161/HYPERTENSIONAHA.107.094011|pmid=18474829|citeseerx=10.1.1.547.1622}} Intentional weight loss is associated with cognitive performance improvements in overweight and obese individuals.{{cite journal |last1=Veronese |first1=N |last2=Facchini |first2=S |last3=Stubbs |first3=B |last4=Luchini |first4=C |last5=Solmi |first5=M |last6=Manzato |first6=E |last7=Sergi |first7=G |last8=Maggi |first8=S |last9=Cosco |first9=T |last10=Fontana |first10=L |title=Weight loss is associated with improvements in cognitive function among overweight and obese people: A systematic review and meta-analysis. |journal=Neuroscience & Biobehavioral Reviews |date=January 2017 |volume=72 |pages=87–94 |doi=10.1016/j.neubiorev.2016.11.017 |pmid=27890688|s2cid=207093523 |url=http://arro.anglia.ac.uk/701220/1/Veronese%20et%20al%202016%20NBBR%20weight%20loss%20and%20cognition%20accepted.pdf }}

• Anorexia
• Cigarette smoking for weight loss
• Weight gain

{{Reflist}}

{{Medical resources

| ICD10 = {{ICD10|R|63|4}}

| ICD9 = {{ICD9|783.21}}

| DiseasesDB=28440

| MeSH=D015431

}}

{{Commons category}}

{{Wikibooks|Lentis/The Weight Loss Industry in the United States}}

{{Wikibooks|Fundamentals of Human Nutrition/Weight management}}

• [http://win.niddk.nih.gov/publications/index.htm Weight-control Information Network] {{Webarchive|url=https://web.archive.org/web/20150212190429/http://win.niddk.nih.gov/publications/index.htm |date=12 February 2015 }} U.S. National Institutes of Health
• [https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0032508/ Nutrition in cancer care, US National Library of Medicine]
• {{MedlinePlusEncyclopedia|003107|Weight loss - unintentional}}

{{Nutritional pathology}}

{{Authority control}}

Category:Dietetics

Category:Obesity

Category:Symptoms and signs