BOSTON — Losing weight, in many contexts, is a positive. Whether looking to slim down for the summer or find a few hidden abs, weight loss routinely ranks among the most common goals people work toward, usually through a mix of dieting and exercise. However, if you’ve been losing weight without even trying lately, a new study suggests it’s time to see a doctor. Scientists at the Dana-Farber Cancer Institute have found an association between unintentional weight loss and an increased risk of a cancer diagnosis over the next year.
“If you are losing weight and you aren’t trying to lose weight by making changes in your exercise routine or diet, people should see their doctor to consider possible causes,” says lead investigator Brian Wolpin, MD, MPH, Director of the Gastrointestinal Cancer Center at Dana-Farber and Director of the Hale Family Center for Pancreatic Cancer Research, in a media release. “There are many conditions that can result in unexpected weight loss. Your doctor can determine if there is something that needs evaluation.”
In comparison with other participants who did not lose weight, recent weight loss showed an association with a significant increase in the risk of numerous cancers, including upper gastrointestinal tract (including esophageal, stomach, liver, biliary tract, and pancreatic cancer), hematological (including non-Hodgkin lymphoma, multiple myeloma, and leukemia), colorectal, and lung cancers. However, recent weight loss did not correlate with an increased risk of other cancers (breast, genitourinary, brain, melanoma).
“Unexpected weight loss can come from cancer or many other conditions,” Dr. Wolpin explains. “Sometimes weight loss is due to more exercise or a healthier diet, and this can be beneficial to people’s health. However, when a patient experiences unintentional weight loss not due to healthier behaviors, seeing your primary care doctor is appropriate, so they can determine whether additional evaluation is necessary for other causes of weight loss, including cancer.”
Study authors analyzed a total of 157,474 people who participated in two large longitudinal studies: The Nurses’ Health Study, which began enrolling middle-aged nurses (ages 30-55) in 1976, and The Health Professionals Follow-Up Study, which enrolled male health professionals (ages 40-75) beginning in 1986. The researchers in charge of both projects tracked participants until 2016.
Participants reported their weight every other year using a biennial questionnaire that included questions related to physical activity. The questionnaire also asked about dietary changes every four years. That data, in particular, is what made it possible for Dr. Wolpin and his team to analyze each person’s level of weight loss-promoting behaviors. Researchers divided these behaviors into different categories: “high” for people making both dietary improvements and increases in physical activity, “medium” if they made just one change, and “low” if they made no changes to either diet or exercise.
“We wanted to differentiate healthy weight loss from unhealthy weight loss,” concludes Qiaoli Wang, MD, PhD, a research fellow at Dana-Farber and the manuscript’s first author. “Healthy weight loss can come from dietary changes or increased exercise. But unhealthy weight loss that occurs unexpectedly can be due to an underlying cancer.”
It’s very common for advanced cancer patients to lose weight, but weight loss usually isn’t thought of as an early-stage cancer symptom. This project found that similar levels of weight loss occurred before diagnosis of both early and late-stage cancer disease. Early detection and treatment of cancer can increase a patient’s survival odds significantly. These findings indicate unintentional weight loss could be a sign of developing cancer that could help lead to a much earlier diagnosis when there’s a chance for more effective treatment.
Precisely how and why cancer results in unintended weight loss varies depending on the type of cancer in question. Still, this project strengthened findings from past research that connected unexpected weight loss with an increased cancer risk. During prior studies, doctors collected weight data from patients potentially seeking out care for an illness. This time around, weight data collection continued prospectively and routinely for decades, and it was not dependent on doctor visits. This study also accounted for all varieties of cancer. All that being acknowledged, researchers admit the two analyzed studies focused solely on health professionals, which is not a group that is fully representative of the U.S. population.
The study is published in JAMA.