Unintentional weight loss may be a warning sign of cancer, according to a recent large-scale study.

When someone loses weight without planning to and without making changes to their diet or exercise routine, it is considered an unintentional weight loss.

Earlier studies have shown an association between weight loss and a cancer diagnosis.

Among the health professionals examined in a recent study published in the journal JAMA Network, researchers noted that those who lost over 10% of their body weight in the past two years were at a greater risk of developing cancer in the subsequent 12 months compared to those who did not have weight loss.

The risk of developing cancer in the upper gastrointestinal tract was particularly common among participants with recent weight loss compared to those without.

The researchers evaluated 157,000 participants who were part of the Nurse's Health Study or the Health Professional's Follow-Up Study, who had a median age of 62.

During the follow-up (of 1.64 million person-years), researchers identified 15,809 new cancer cases, resulting in an incidence rate of 964 cases per 100,000 person-years.

"Among participants diagnosed with cancer during the year following weight assessment, 15% had weight loss of greater than 5.0% of body weight and 5% had weight loss of greater than 10.0% before cancer diagnosis. The mean length of time between reported weight change and subsequent cancer diagnosis was 6.5 months (SD, 3.5 months) for participants with weight loss of 5.1% to 10.0% of body weight and was 6.0 months (SD, 3.5 months) for those with weight loss of greater than 10.0%," the researchers wrote.

"Compared with no recent weight loss, any recent weight loss of greater than 10.0% was significantly associated with higher rates of specific cancer diagnoses," they added.

The risk of getting cancer was higher in the initial 12 months after weight loss compared to the following two years. The researchers could not find an association between recent weight loss and certain types of cancers including breast, genital, urinary, brain and melanoma.

There was no association between the amount of weight lost and the cancer stage.

The study had certain limitations. The body weights of the participants were based on self-reported data, which were not verified with measurement. Also, the weights were assessed only once in two years, so the rapidity of weight loss could not be precisely determined.

Unintentional weight loss could also be due to other medical conditions such as depression, anxiety, eating disorders, diabetes, celiac disease, irritable bowel syndrome, overactive thyroid and heart failure.

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