Many people associate unexplained weight loss with cancer. Though unintentional weight loss can be a warning sign of cancer, there are other reasons for unexplained weight loss as well.

Read on to learn more about unexplained weight loss, including when it’s concerning and its other causes.

Your weight can fluctuate for various reasons. A life-changing or stressful event can cause you to lose weight unintentionally. Even having an especially busy schedule for a while can cause a temporary change in your food intake and activity level, causing you to lose a few pounds.

There aren’t any firm guidelines. But some experts follow the rule of thumb that an unintentional weight loss of more than five percent of your body weight in a period of six months to a year calls for a medical evaluation.

According to the American Cancer Society, unexplained weight loss is often the first noticeable symptom of cancers of the esophagus, pancreas, stomach, and lung.

Other cancers, such as ovarian cancer, are more likely to cause weight loss when a tumor grows large enough to press on the stomach. This can make you feel full faster.

Other types of cancer can also cause symptoms that make eating difficult, such as:

  • nausea
  • lack of appetite
  • difficulty chewing or swallowing

Cancer also increases inflammation. Inflammation is part of your body’s immune response to a tumor, which produces pro-inflammatory cytokines and alters your body’s metabolism. This disrupts the hormones that regulate your appetite. It also promotes the breakdown of fat and muscle.

Finally, a growing tumor uses a significant amount of your body’s energy, which may increase your resting energy expenditure (REE). REE is how much energy your body burns at rest.

Not all cancers cause symptoms in their early stages. And those that do often cause vague symptoms that are commonly caused by less serious conditions.

Cancers known to cause unintended weight loss early on will likely also cause other symptoms.

These include:

Again, while these can all be early cancer symptoms, they can also be caused by a range of other conditions, most of which are much more common — and less serious — than cancer.

Most cases of unexplained weight loss aren’t caused by cancer. Still, it’s a good idea to follow up with your healthcare provider about any significant weight loss that can’t be explained by changes in your diet or activity levels.

Generally, losing more than 5 percent of your body weight within 6 to 12 months warrants a visit. And if you’re an older adult with other health issues, even a smaller amount of weight loss may be reason to see your healthcare provider.

Your provider will begin by taking your medical history, including any medications you are taking. Urine and blood tests, as well as imaging scans, can find signs of cancer or another condition that may be behind your weight loss.

Seek immediate treatment if your weight loss is accompanies by any of the following symptoms:

It’s understandable to worry about cancer when you have unexplained weight loss, but there are many other possible causes. If you’re concerned about your weight loss and have other concerning symptoms, make an appointment with your healthcare provider.