While shedding a few pounds might typically be seen as beneficial, unintentional weight loss can be an indicator of serious health issues, according to Christine Goukasian, senior dietitian at UCLA’s Division of Clinical Nutrition. Goukasian cautions that unexplained weight loss without changes in diet, physical activity, or an intention to lose weight can be a “red flag” and warrants further investigation.

Goukasian notes that slight fluctuations in weight due to water retention, hormonal shifts, and daily activities are normal. However, “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,” she said in a UCLA news release.

Unexpected weight loss can be particularly concerning in older adults. Nearly 20% of older individuals experience unintentional weight loss, a figure that escalates to 60% among seniors in community housing, where underlying health issues are often more prevalent.

The leading cause of unintentional weight loss is cancer, which accounts for over a third of cases in patients seeking medical advice for sudden weight loss. According to UCLA data, weight loss is often an early warning sign, with about 40% of cancer diagnoses beginning with unexpected weight loss. Colon, pancreatic, and lung cancers, even in their early stages, may present with this symptom.

Beyond cancer, gastrointestinal (GI) issues also play a significant role, accounting for 10% to 20% of cases. Conditions such as chronic diarrhea, inflammatory bowel disease, and celiac disease can lead to weight loss, as can the overuse of laxatives, often linked to eating disorders.

Mental health disorders, including anxiety, depression, and obsessive-compulsive disorder, can also contribute to a decreased appetite. “If you don’t have much interest in eating or are sleeping so much that you’re missing meals, you are going to lose weight,” Goukasian explains. Medications prescribed for mental health can further affect appetite, taste, and even trigger nausea.

In addition to these causes, other culprits include thyroid disorders, diabetes, dementia, gum disease, and swallowing difficulties. Financial struggles or limited access to adequate food can also contribute to unintentional weight loss, particularly in vulnerable populations.

“Not all weight loss is because of a life-threatening disease,” Goukasian assures, emphasizing that many underlying causes are treatable. To identify the source of unintentional weight loss, a healthcare provider may conduct a comprehensive physical and mental health assessment, along with blood work, urine tests, and imaging.

“Identifying an underlying cause of unexplained weight loss can be challenging and may require a lot of diagnostic testing and time,” Goukasian acknowledges. “But the important thing is that you're being proactive about your health and paying attention to your body.”

If you or a loved one is experiencing unintentional weight loss, medical experts encourage consulting a healthcare provider promptly to address potential underlying health issues before they worsen.