非故意性体重减轻通常定义为在之前 6 至 12 个月内患者体重至少减轻了正常体重的 5%，而且并不是治疗已知疾病的预期结果。[1]Wong CJ. Involuntary weight loss. Med Clin North Am. 2014;98:625-643.http://www.ncbi.nlm.nih.gov/pubmed/24758965?tool=bestpractice.com 在诊断上存在困难，因为虽然获得详尽的病史和查体可能帮助发现某种潜在疾病，但也可能仍然难以查明病因，只有通过进一步的检查或随着时间的推移才能发现病因，或者根本无法发现病因。最紧迫的问题是评估是否存在肿瘤或其他疾病，如果存在，早期诊断可能会带来更好的结局。非故意性体重减轻可有广泛的病因，包括躯体疾病、精神疾病和社会因素。这些情况可能单独发生，也可能同时存在。
阅读更多
分类
关于非故意性体重减轻，没有正式的统一定义；但是，患者和治疗医生必须确认患者没有有意地减轻体重。 在一系列的病例研究中，判断体重减轻的标准被定义为与正常体重相比体重减轻 5%~10%。[2]Marton KI, Sox HC, Krupp JR. Involuntary weight loss: diagnostic and prognostic significance. Ann Intern Med. 1981;95:568-574.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;146:186-187.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;43:329-337.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;13:240-245.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-S29.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;53:51-54.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.0175125http://www.ncbi.nlm.nih.gov/pubmed/28388637?tool=bestpractice.com类似地，也没有严格定义非故意性体重减轻应在多长时间内出现；但是，大多数病例系列研究使用的标准为在之前的 3 至 12 个月内出现体重减轻。
相关症状包括恶病质和肌少症。 恶病质是一种体重减轻综合征，其特征为因存在一种潜在疾病（如某些类型的癌症或晚期心力衰竭）的代谢作用而出现肌肉组织重量减少。[10]Evans WJ, Morley JE, Argiles J, et al. Cachexia: a new definition. Clin Nutr. 2008;27:793-799.http://www.ncbi.nlm.nih.gov/pubmed/18718696?tool=bestpractice.com 尽管所有恶病质患者都会出现非故意性体重减轻，但并不是所有非故意性体重减轻患者都有恶病质。 肌少症是一种以肌肉组织重量减少和功能衰退为表现的老年综合征，可能伴或不伴非故意性体重减轻。
营养不良的共识定义将非故意性体重减轻（3 个月内减轻＞5%，或非确定时间内减轻＞10%）纳入诊断标准之一。[11]Cederholm T, Bosaeus I, Barazzoni R, et al. Diagnostic criteria for malnutrition: an ESPEN consensus statement. Clin Nutr. 2015;34:335-340.http://www.clinicalnutritionjournal.com/article/S0261-5614%2815%2900075-8/fulltexthttp://www.ncbi.nlm.nih.gov/pubmed/25799486?tool=bestpractice.com
流行病学
在基于人群的队列研究中，非故意性体重减轻的发生率为 7% 至 13%，差异可归因为人口统计学因素和随访持续的时间。[12]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;138:383-389.http://annals.org/article.aspx?articleid=716098http://www.ncbi.nlm.nih.gov/pubmed/12614090?tool=bestpractice.com[13]Wannamethee SG, Shaper AG, Lennon L. Reasons for intentional weight loss, unintentional weight loss, and mortality in older men. Arch Intern Med. 2005;165:1035-1040.http://archinte.jamanetwork.com/article.aspx?articleid=1152796http://www.ncbi.nlm.nih.gov/pubmed/15883243?tool=bestpractice.com[14]Sahyoun NR, Serdula MK, Galuska DA. The epidemiology of recent involuntary weight loss in the United States population. J Nutr Health Aging. 2004;8:510-517.http://www.ncbi.nlm.nih.gov/pubmed/15543425?tool=bestpractice.com 对于大多数符合临床表现定义的患者（例如在前 6 个月内发生体重减轻），发生率约为 7%。[14]Sahyoun NR, Serdula MK, Galuska DA. The epidemiology of recent involuntary weight loss in the United States population. J Nutr Health Aging. 2004;8:510-517.http://www.ncbi.nlm.nih.gov/pubmed/15543425?tool=bestpractice.com 在超重和肥胖受试者中，[12]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;138:383-389.http://annals.org/article.aspx?articleid=716098http://www.ncbi.nlm.nih.gov/pubmed/12614090?tool=bestpractice.com 以及出现非故意性体重减轻的老年患者中。[15]Wijnhoven HA, van Zon SK, Twisk J, et al. Attribution of causes of weight loss and weight gain to 3-year mortality in older adults: results from the Longitudinal Aging Study Amsterdam. J Gerontol A Biol Sci Med Sci. 2014;69:1236-1243.http://www.ncbi.nlm.nih.gov/pubmed/24522392?tool=bestpractice.com 对于最近（即，6 个月内）出现非故意性体重减轻的患者，体重减轻 5% 或以上会使死亡率增加。[14]Sahyoun NR, Serdula MK, Galuska DA. The epidemiology of recent involuntary weight loss in the United States population. J Nutr Health Aging. 2004;8:510-517.http://www.ncbi.nlm.nih.gov/pubmed/15543425?tool=bestpractice.com 非故意性体重减轻与接受结肠直肠手术和播散性癌症手术患者的围手术期并发症增加有关。[16]Moghadamyeghaneh Z, Hanna MH1, Hwang G, et al. Outcome of preoperative weight loss in colorectal surgery. Am J Surg. 2015;210:291-297.http://www.ncbi.nlm.nih.gov/pubmed/25990792?tool=bestpractice.com[17]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
与非故意性体重减轻形成显著对比的是，在许多国家/地区肥胖迅速蔓延，尝试有意减轻体重却不成功的经历颇为常见。此外，初级保健机构可能未充分识别出非故意性体重减轻。[18]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;22:316-322.http://hijournal.bcs.org/index.php/jhi/article/view/137/840http://www.ncbi.nlm.nih.gov/pubmed/26577421?tool=bestpractice.com
病理生理学
病理生理学表现因病因的不同而有所不同。 保持体重平稳是一个复杂的过程，影响因素包括可获得的食物、体育活动、所处的环境和肽类物质对激素水平的调节（如瘦素、胆囊收缩素和胃饥饿素）。[19]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;97:745-755.http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3319208/http://www.ncbi.nlm.nih.gov/pubmed/22238401?tool=bestpractice.com 由于恶病质而出现的非故意性体重减轻与细胞因子（例如肿瘤坏死因子 α）有关，这种因子会抑制食欲，促进肌肉和脂肪分解，增加能量消耗。[20]Fearon KC, Glass DJ, Guttridge DC. Cancer cachexia: mediators, signaling, and metabolic pathways. Cell Metabolism. 2012;16:153-166.http://www.ncbi.nlm.nih.gov/pubmed/22795476?tool=bestpractice.com[21]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;37:1084-1104.http://www.ncbi.nlm.nih.gov/pubmed/15743680?tool=bestpractice.com 在恶病质综合征患者中，正常的稳态调节机制被打乱，而这些机制在单纯性热量摄入不足而导致的体重减轻的患者中是正常的。
鉴别诊断
鉴别诊断所涉及的范围极广。 在病例系列研究中，最常见的病因是：
应考虑的其他病因包括：
