Weight loss

Last revised by Dr Daniel J Bell on 14 Oct 2021

A clinical presentation of weight loss is extremely common and often a source of marked anxiety for the patient. The commonest cause of unintentional weight loss (UWI) is gastrointestinal tract disease, and not malignancy.

The published literature lacks a consistent definition of what constitutes clinically-significant unintended weight loss. A loss of body weight of ≥5% in ≤6 months is often employed for this purpose 2. Although in the context of lymphoma, the presence of weight loss, as one of the B symptoms, is defined as a loss of body weight of ≥10% within six months 3.

Although severe weight loss (in adults) is almost always a feature of cachexia, the latter term refers specifically to a complex metabolic syndrome seen in the context of malignancy and other chronic diseases in which there is severe decrease in muscle bulk (sarcopenia5

  • gastrointestinal
  • malignancy
  • infections
  • psychosocial
  • endocrine
  • cardiopulmonary
  • alcohol excess
  • rheumatological 
  • miscellaneous
  • dieting/starvation
  • physical exercise
  • surgery: bariatric surgery, cosmetic surgery (e.g. liposuction)
  • medications (purgatives, anxiolytics, diuretics, etc.)
  • self-induced vomiting

On cross-sectional imaging, the most striking feature of a patient who has lost a large amount of weight is usually the distinct lack of subcutaneous and intra-abdominal fat. This often makes studies difficult to read as the solid organs, bowel loops and nodes may be difficult to separate visually, especially on non-contrast CT examinations.

The use of imaging to identify the underlying cause of unintentional weight loss is increasingly common. In a retrospective study of 200 patients with unexplained weight loss, from 2018, whole body CT was able to elucidate the primary cause in a third of patients (33.5%) 4.

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