Unintentional weight loss is often defined as weight loss of at least 5% of the patient’s usual body weight that occurs within the preceding 6 to 12 months, and that is not the expected consequence of treatment of a known illness.[1]Wong CJ. Involuntary weight loss. Med Clin North Am. 2014;98:625-43.
http://www.ncbi.nlm.nih.gov/pubmed/24758965?tool=bestpractice.com
Unintentional weight loss is a diagnostic challenge because, while an underlying illness may be found after a thorough history and physical examination, the aetiology may remain elusive and only be discovered through additional testing, the passage of time, or not at all. The most pressing concern is the assessment for the presence of cancer or other conditions for which early diagnosis may lead to better outcomes. There is a broad range of causes of unintentional weight loss including medical diseases, psychiatric illnesses, and social factors. These conditions may occur in isolation or in combination.
Classification
There is no formal consensus definition of unintentional weight loss; however, the weight loss must be considered unintentional by the patient and treating practitioner. The degree of unintentional weight loss has been defined in case series as being between 5% and 10% weight loss compared with usual body weight.[2]Marton KI, Sox HC, Krupp JR. Involuntary weight loss: diagnostic and prognostic significance. Ann Intern Med. 1981;95:568-74.
http://www.ncbi.nlm.nih.gov/pubmed/7294545?tool=bestpractice.com
[3]Rabinovitz M, Pitlik SD, Leifer M, et al. Unintentional weight loss: a retrospective analysis of 154 cases. Arch Intern Med. 1986;146:186-7.
http://www.ncbi.nlm.nih.gov/pubmed/3942450?tool=bestpractice.com
[4]Thompson MP, Morris LK. Unexplained weight loss in the ambulatory elderly. J Am Geriatr Soc. 1991;39:497-500.
http://www.ncbi.nlm.nih.gov/pubmed/2022802?tool=bestpractice.com
[5]Wallace JI, Schwartz RS, LaCroix AZ, et al. Involuntary weight loss in older outpatients: incidence and clinical significance. J Am Geriatr Soc. 1995;43:329-37.
http://www.ncbi.nlm.nih.gov/pubmed/7706619?tool=bestpractice.com
[6]Bilbao-Garay J, Barba R, Losa-Garcia JE, et al. Assessing clinical probability of organic disease in patients with involuntary weight loss: a simple score. Eur J Intern Med. 2002;13:240-5.
http://www.ncbi.nlm.nih.gov/pubmed/12067819?tool=bestpractice.com
[7]Chen SP, Peng LN, Lin MH, et al. Evaluating probability of cancer among older people with unexplained, unintentional weight loss. Arch Gerontol Geriatr. 2010;50(suppl 1):S27-9.
http://www.ncbi.nlm.nih.gov/pubmed/20171452?tool=bestpractice.com
[8]Wu JM, Lin MH, Peng LN, et al. Evaluating diagnostic strategy of older patients with unexplained unintentional body weight loss: a hospital-based study. Arch Gerontol Geriatr. 2011;53:51-4.
http://www.ncbi.nlm.nih.gov/pubmed/21071102?tool=bestpractice.com
[9]Bosch X, Monclús E, Escoda O, et al. Unintentional weight loss: Clinical characteristics and outcomes in a prospective cohort of 2677 patients. PLoS One. 2017 Apr 7;12(4):e0175125.
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0175125
http://www.ncbi.nlm.nih.gov/pubmed/28388637?tool=bestpractice.com
Similarly, there is no strict definition of the time period in which the unintentional weight loss should occur; however, most case series used the criteria of weight loss developing within the preceding 3 to 12 months.
Related syndromes include cachexia and sarcopenia. Cachexia is a syndrome of weight loss characterised by decreased muscle mass in the presence of the metabolic effects of an underlying illness such as some types of cancer or advanced heart failure.[10]Evans WJ, Morley JE, Argiles J, et al. Cachexia: a new definition. Clin Nutr. 2008;27:793-9.
http://www.ncbi.nlm.nih.gov/pubmed/18718696?tool=bestpractice.com
[11]Arends J, Strasser F, Gonella S, et al. Cancer cachexia in adult patients: ESMO clinical practice guidelines(☆). ESMO Open. 2021 Jun;6(3):100092.
https://www.esmoopen.com/article/S2059-7029(21)00049-1/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/34144781?tool=bestpractice.com
[12]Vest AR, Chan M, Deswal A, et al. Nutrition, obesity, and cachexia in patients with heart failure: a consensus statement from the Heart Failure Society of America Scientific Statements Committee. J Card Fail. 2019 May;25(5):380-400.
http://www.ncbi.nlm.nih.gov/pubmed/30877038?tool=bestpractice.com
While all patients with cachexia have unintentional weight loss, not all patients with unintentional weight loss have cachexia. Sarcopenia is a geriatric syndrome of diminished muscle mass and function, which may or may not be accompanied by unintentional weight loss.[13]Cruz-Jentoft AJ, Bahat G, Bauer J, et al. Sarcopenia: revised European consensus on definition and diagnosis. Age Ageing. 2019 Jan 1;48(1):16-31.
https://academic.oup.com/ageing/article/48/1/16/5126243?login=false
http://www.ncbi.nlm.nih.gov/pubmed/30312372?tool=bestpractice.com
A consensus definition of malnutrition includes unintentional weight loss (>5% in 3 months, or >10% of indefinite time) as a component of one set of diagnostic criteria.[14]Cederholm T, Bosaeus I, Barazzoni R, et al. Diagnostic criteria for malnutrition: an ESPEN consensus statement. Clin Nutr. 2015;34:335-40.
http://www.clinicalnutritionjournal.com/article/S0261-5614%2815%2900075-8/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/25799486?tool=bestpractice.com
In the US, the Centers for Medicare and Medicaid Services require that long-term care facilities conduct an assessment when a resident has an unplanned weight loss problem (5% change in 30 days or 10% change in 180 days), together with another area of decline.[15]Centers for Medicare and Medicaid Services. State operations manual, appendix PP - guidance to surveyors for long term care facilities. Feb 2023 [internet publication].
https://www.cms.gov/medicare/provider-enrollment-and-certification/guidanceforlawsandregulations/downloads/appendix-pp-state-operations-manual.pdf
Epidemiology
In population-based cohort studies, the prevalence of unintentional weight loss varies between 7% and 13%, with differences attributable to both demographics and duration of follow-up.[16]Gregg EW, Gerzoff RB, Thompson TJ, et al. Intentional weight loss and death in overweight and obese U.S. adults 35 years of age and older. Ann Intern Med. 2003;138:383-9.
http://annals.org/article.aspx?articleid=716098
http://www.ncbi.nlm.nih.gov/pubmed/12614090?tool=bestpractice.com
[17]Wannamethee SG, Shaper AG, Lennon L. Reasons for intentional weight loss, unintentional weight loss, and mortality in older men. Arch Intern Med. 2005;165:1035-40.
http://archinte.jamanetwork.com/article.aspx?articleid=1152796
http://www.ncbi.nlm.nih.gov/pubmed/15883243?tool=bestpractice.com
[18]Sahyoun NR, Serdula MK, Galuska DA. The epidemiology of recent involuntary weight loss in the United States population. J Nutr Health Aging. 2004;8:510-7.
http://www.ncbi.nlm.nih.gov/pubmed/15543425?tool=bestpractice.com
The prevalence in older adults (those aged >65 years) is reportedly 15% to 20%; however, clinical and epidemiological studies have reported even higher prevalence in certain populations, with as many as 27% of community-dwelling elderly people and 50% to 60% of nursing home residents being affected.[19]Alibhai SM, Greenwood C, Payette H. An approach to the management of unintentional weight loss in elderly people. CMAJ. 2005 Mar 15;172(6):773-80.
https://www.doi.org/10.1503/cmaj.1031527
http://www.ncbi.nlm.nih.gov/pubmed/15767612?tool=bestpractice.com
[20]Bouras EP, Lange SM, Scolapio JS. Rational approach to patients with unintentional weight loss. Mayo Clin Proc. 2001 Sep;76(9):923-9.
https://www.doi.org/10.4065/76.9.923
http://www.ncbi.nlm.nih.gov/pubmed/11560304?tool=bestpractice.com
For patients with the most clinically applicable presentation (i.e., weight loss occurring within the preceding 6 months), the prevalence is approximately 7%.[18]Sahyoun NR, Serdula MK, Galuska DA. The epidemiology of recent involuntary weight loss in the United States population. J Nutr Health Aging. 2004;8:510-7.
http://www.ncbi.nlm.nih.gov/pubmed/15543425?tool=bestpractice.com
A significant association between mortality and unintentional weight loss in older people, and in overweight and obese subjects, has been demonstrated in sub-group analysis of one systematic review and meta-analysis.[21]De Stefani FDC, Pietraroia PS, Fernandes-Silva MM, et al. Observational evidence for unintentional weight loss in all-cause mortality and major cardiovascular events: a systematic review and meta-analysis. Sci Rep. 2018 Oct 18;8(1):15447.
https://www.nature.com/articles/s41598-018-33563-z
http://www.ncbi.nlm.nih.gov/pubmed/30337578?tool=bestpractice.com
In an earlier observational study, patients with recent unintentional weight loss (i.e., within 6 months), a weight loss of ≥5% was associated with an increase in subsequent mortality.[18]Sahyoun NR, Serdula MK, Galuska DA. The epidemiology of recent involuntary weight loss in the United States population. J Nutr Health Aging. 2004;8:510-7.
http://www.ncbi.nlm.nih.gov/pubmed/15543425?tool=bestpractice.com
Unintentional weight loss has been associated with increased perioperative complications in patients undergoing gynecological surgery, colorectal surgery, and surgery for disseminated cancer.[22]Pache B, Grass F, Hübner M, et al. Prevalence and consequences of preoperative weight loss in gynecologic surgery. Nutrients. 2019 May 17;11(5):1094.
https://www.mdpi.com/2072-6643/11/5/1094
http://www.ncbi.nlm.nih.gov/pubmed/31108841?tool=bestpractice.com
[23]Moghadamyeghaneh Z, Hanna MH1, Hwang G, et al. Outcome of preoperative weight loss in colorectal surgery. Am J Surg. 2015;210:291-7.
http://www.ncbi.nlm.nih.gov/pubmed/25990792?tool=bestpractice.com
[24]Thirunavukarasu P, Sanghera S, Singla S, et al. Pre-operative unintentional weight loss as a risk factor for surgical outcomes after elective surgery in patients with disseminated cancer. Int J Surg. 2015;18:7-13.
http://www.ncbi.nlm.nih.gov/pubmed/25865083?tool=bestpractice.com
Unintentional weight loss has been associated with high rates of hospital admission in an outpatient cohort and in patients with dementia in care home settings.[25]Duan R, Zhang Q, Zhu J, et al. The association between GLIM criteria-defined malnutrition and 2-year unplanned hospital admission in outpatients with unintentional weight loss: a retrospective cohort study. JPEN J Parenter Enteral Nutr. 2023 Jul;47(5):624-34.
http://www.ncbi.nlm.nih.gov/pubmed/37094973?tool=bestpractice.com
[26]Afonso-Argilés FJ, Meyer G, Stephan A, et al. Emergency department and hospital admissions among people with dementia living at home or in nursing homes: results of the European RightTimePlaceCare project on their frequency, associated factors and costs. BMC Geriatr. 2020 Nov 5;20(1):453.
https://bmcgeriatr.biomedcentral.com/articles/10.1186/s12877-020-01835-x
http://www.ncbi.nlm.nih.gov/pubmed/33153444?tool=bestpractice.com
Unintentional weight loss represents a striking contrast to the epidemics of obesity in many countries and the commonplace experience of unsuccessful attempts at intentional weight reduction. Furthermore, unintentional weight loss may be under-recognised in the primary care setting.[27]El-Kareh R, Pazo V, Wright A, et al. Losing weights: failure to recognize and act on weight loss documented in an electronic health record. J Innov Health Inform. 2015;22:316-22.
http://hijournal.bcs.org/index.php/jhi/article/view/137/840
http://www.ncbi.nlm.nih.gov/pubmed/26577421?tool=bestpractice.com
Pathophysiology
The pathophysiology varies depending on the aetiology. Weight homeostasis is a complex process that includes the availability of food, physical activity, possible environmental exposures, and hormonal control with peptides such as leptin, cholecystokinin, and ghrelin.[28]Guyenet SJ, Schwartz MW. Regulation of food intake, energy balance, and body fat mass: implications for the pathogenesis and treatment of obesity. J Clin Endocrinol Metab. 2012;97:745-55.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319208
http://www.ncbi.nlm.nih.gov/pubmed/22238401?tool=bestpractice.com
Unintentional weight loss owing to cachexia is associated with cytokines (e.g., tumour necrosis factor-alpha) that suppress appetite, promote muscle and fat breakdown, and increase energy expenditure.[29]Fearon KC, Glass DJ, Guttridge DC. Cancer cachexia: mediators, signaling, and metabolic pathways. Cell Metabolism. 2012;16:153-66.
http://www.ncbi.nlm.nih.gov/pubmed/22795476?tool=bestpractice.com
[30]Argiles JM, Busquets S, Felipe A, et al. Molecular mechanisms involved in muscle wasting in cancer and ageing: cachexia versus sarcopenia. Int J Biochem Cell Biol. 2005;37:1084-104.
http://www.ncbi.nlm.nih.gov/pubmed/15743680?tool=bestpractice.com
Normal homeostasis signaling is disrupted in cachexia syndromes, while these mechanisms are preserved in the setting of weight loss due purely to inadequate caloric intake.
Differential diagnosis
The differential diagnosis is extremely broad. In case series, the most common aetiologies are:[31]McMinn J, Steel C, Bowman A. Investigation and management of unintentional weight loss in older adults. BMJ. 2011 Mar 29;342:d1732.
http://www.ncbi.nlm.nih.gov/pubmed/21447571?tool=bestpractice.com
Other aetiologies that should be considered include:
Cachexia syndromes associated with organ failure (e.g., heart failure, chronic obstructive pulmonary disease, stage 5 chronic kidney disease)
Endocrinopathies (e.g., hyperthyroidism, diabetes mellitus, adrenal insufficiency)
Serious infections (e.g., tuberculosis, HIV)
Medication adverse effects
Substance misuse
Social factors that prevent adequate access to food
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