Your weight is a critical piece of your health puzzle — it can signal a problem or be the cause of health issues. If your weight unexpectedly drops without a reason, you may have an underlying health problem.
“Unexplained weight loss is a red flag,” says Christine Goukasian, RDN, MS, senior dietitian with the UCLA Division of Clinical Nutrition. “It’s not typical to have a noticeable drop in weight without changing how much you’re eating, being more physically active or trying to lose weight.”
When is weight loss concerning?
It’s normal for weight to fluctuate daily due to water retention, hormones and other variables. But most people experience weight changes of 2 to 3 pounds in either direction.
“Weight loss becomes a concern when it’s 10 pounds or at least 5% of your original weight during a six-to-12-month period,” Goukasian says.
Older adults are at higher risk for unexplained weight loss, especially if they live in a community living setting. Studies show that as many as 20% of older adults experience unexplained weight loss. For nursing home residents, that number increases to 60%, likely because the prevalence of issues causing unintentional weight loss (including cancer, gastrointestinal conditions and psychological issues) may be greater in this population.
What can cause sudden weight loss?
Weight loss cannot always be explained, especially in older adults. But, in nearly 75% of cases, an identifiable underlying issue causes the weight loss.
The most common causes of unexpected weight loss include:
Cancer
Cancer is the most common cause of unintentional weight loss — more than 35% of people who see their doctor for weight loss have undiagnosed cancer. Adults with unexplained weight loss are at least 12 times more likely to have cancer than people who aren’t experiencing weight loss.
Weight loss is often the first symptom of cancer — approximately 40% of cancer diagnoses begin this way. While many people believe that cancer-related weight loss signals advanced cancer, it can also occur in the early stage of some cancers. Researchers report that people with early-stage colorectal, pancreatic and lung cancer have reported weight loss. Recognizing unexpected weight loss can help identify and treat cancer earlier.
Digestive diseases and conditions
Gastrointestinal (GI) issues account for 10% to 20% of unexpected weight loss cases. Digestive diseases can cause inflammation and malabsorption, which may affect your metabolism and hinder the body’s ability to take in calories and macronutrients.
GI conditions that commonly lead to sudden weight loss include:
- Celiac disease
- Chronic diarrhea
- Inflammatory bowel diseases
- Overuse of laxatives, often suggesting an eating disorder
Mental health issues
Mental health disorders are responsible for unintentional weight loss approximately 10% to 23% of the time. Your appetite may be affected by:
“If you don’t have much interest in eating or sleeping so much you are missing meals, you are going to lose weight,” Goukasian says.
For some people, weight loss can also be the result of side effects associated with medications used to treat mental health disorders. Some medicines can cause nausea, reduce appetite or tamper with your sense of smell and taste.
Other possible causes of unintentional weight loss
While cancer and GI issues and mental health cause most unintentional weight loss, there are many other reasons you might suddenly lose weight, including:
- Dementia, due to changes in mealtime habits
- Endocrine issues, including thyroid disorders and diabetes
- Medication side effects, which can cause dry mouth, vomiting, nausea or altered senses that interfere with eating
- Oral disorders, including gum disease, dysphagia (trouble swallowing) or any condition that makes it uncomfortable to eat
- Social factors, such as alcoholism, financial limitations or difficulty getting food
“There are so many factors that influence your weight and can contribute to weight loss,” Goukasian says. “Not all weight loss is because of a life-threatening disease. Many times, the underlying cause is treatable or manageable.”
What to do if you are losing weight without trying
If you’ve lost a concerning amount of weight in recent months, the first step should be consulting with your primary care physician (PCP). To pinpoint the cause of your weight loss, your physician may recommend a diagnostic process that includes:
- Physical exam and medical history to identify additional symptoms or risks
- Blood tests to measure important factors such as metabolism and thyroid function
- Urine analysis to identify any infections and check kidney and bladder function
- Mental health screening to pinpoint emotional and mental issues that may interfere with your appetite or eating
- Imaging, such as MRI or a CT scan, to rule out tumors or other diseases
“Identifying an underlying cause of unexplained weight loss can be challenging and may require a lot of diagnostic testing and time,” Goukasian says. “But the important thing is that you’re being proactive about your health and paying attention to your body."
