Rapid Weight Loss: Symptoms & Causes

by John Staughton (BASc, BFA) last updated -

Weight loss can be a goal for most. But unplanned, unexplained, and rapid weight loss can be a sign of deteriorating health or an underlying health condition, and thus a cause for concern.

What is Rapid Weight Loss?

If your body quickly loses weight, especially without you making any lifestyle and diet changes, it is considered to be unhealthy, rapid weight loss. The weight loss rate of 1.1 to 2.2 pounds (0.5 kg to 1 kg) is considered normal and healthy. [1]


However, any unintended loss of body mass might be a symptom of some other serious underlying condition. The condition could also be accompanied by the following symptoms:

  • muscle weakness and fatigue
  • depression
  • slower metabolism
  • loss of appetite
  • increase in illnesses (weakened immune system)
  • a change in your frequency of going to the bathroom

Depending on the root cause of your unexplained weight loss, your symptoms may differ significantly, possibly including shortness of breath, cognitive confusion, stiff muscles, low blood pressure, blood in the stool, abdominal cramps, vomiting, coughing, irregular heartbeat, slow healing of bruises and cuts, numbness, and anxiety. Unexplained weight loss often affects older people or those who have had issues with malnutrition in the past, but as the causes below illustrate, this condition can affect anyone. [2] [3]

Causes of Unexplained Weight Loss

Some of the more worrying causes of unexplained weight loss include diabetes, peptic ulcers, celiac disease, cancer, depression, HIV/AIDS, stomach ulcers, ulcerative colitis, hypo/hyperthyroidism, COPD, Addison’s disease, and rheumatoid arthritis. This is not an exhaustive list, rather some of the most common causes of inexplicable weight loss.


When you first develop diabetes, often before you realize you are suffering from the condition, your body is expelling glucose that it can’t use, which results in frequent urination. Furthermore, to compensate for the lack of nutrients it is absorbing, the body will start to leech nutrients from muscles, which causes a loss in overall weight. [4]

Celiac Disease

This inability of the body to absorb or process gluten also causes inflammation in the gut, which makes nutrient uptake far less efficient. This is often accompanied by diarrhea and stomach upset, which can kill your appetite and result in less calorie intake every day (American Family Physician). Fortunately, going gluten-free is easier now than ever before, given the broader awareness of the Celiac disease in the population. [5]

Woman who has lost weight wearing over-sized denims

Weight loss is good but rapid weight loss indicates an underlying health problem. Photo Credit: Shutterstock

Thyroid Issues

If you suffer from hyperthyroidism, it often means that your body’s metabolism is working too quickly, burning more energy and resources than it actually needs, which makes it difficult to keep up with the calories being demanded by the body. [6]

Eating Disorders

Even if you don’t self-identify having an eating disorder, anorexia is quite common in people who are stressed, overworked or dealing with self-image problems. Consistently cutting back on the quantity of food you eat, without altering any other aspects of your physical fitness or behavioral patterns, can cause rapid weight loss. [7]


When anxiety and depression strike, your appetite is often affected by the flood of stress hormones in the body, making the idea of eating food very unpleasant. When your body begins losing weight, many people suffering from chronic depression don’t even realize it until the weight loss has reached dangerous levels of malnutrition. [8]


The growth of tumors in the gastrointestinal or digestive system can cause inflammation that prevents nutrient absorption, causing food to simply pass through your body, without all the calories being taken in by the body. The general weakness and discomfort of cancerous symptoms can also make eating unpleasant, even negatively affecting the taste of food. According to Elsevier’s The American Journal of Medicine, it can cause sudden unexplained weight loss. This could also happen in the case of lung and pancreatic cancer. [9] [10]

Stomach Problems

Various conditions affecting the stomach, such as ulcerative colitis, stomach ulcers, stomach cancer, peptic ulcers, or parasitic infections like hookworms, can cause severe inflammation in the stomach. According to The Lancet, preventing the proper absorption of nutrients from the food we eat, which will eventually lead to weight loss. [11]


If you suffer from COPD, you may burn up to 10 times as many calories while breathing like a normal person, meaning that your body will often burn more calories than you are taking in a given day, leading to rapid weight loss. [12]

Rheumatoid Arthritis

This autoimmune disease attacks the body’s own tissues, but this isn’t limited to the joints and ligaments. It can also affect tissues in the gut, which are responsible for digestion, making nutrient uptake more difficult, leading to unexplained weight loss. [13]

Addison’s Disease

This condition affects the adrenal glands, which are crucial to many different bodily processes including the production of cortisol, adrenaline, and aldosterone. These are some of the most important hormones in the body, and without their regular presence in the body, it will cause fatigue, loss of appetite and rapid weight loss. [14]


If you are suffering from this condition, the medication you may be prescribed could kill your appetite, or even make it more difficult for your body to absorb nutrients. [15]

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About the Author

John Staughton is a traveling writer, editor, publisher and photographer with English and Integrative Biology degrees from the University of Illinois in Champaign-Urbana (USA). He co-founded the literary journal, Sheriff Nottingham, and now serves as the Content Director for Stain’d Arts, a non-profit based in Denver, Colorado. On a perpetual journey towards the idea of home, he uses words to educate, inspire, uplift and evolve.

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