Significant link found between recent weight loss and increased cancer risk

By Dr. Liji Thomas, MDJan 23 2024

Many patients who present to primary care physicians do so with a history of weight loss in the recent past. With rising rates of cancer detection, a new study that recently appeared in The Journal of the American Medical Association deals with the question of whether recent weight loss is linked to an excess of cancer diagnoses during the subsequent 12 months.

Study: Cancer Diagnoses After Recent Weight Loss. Image Credit: 279photo Studio / Shutterstock

Increasing life expectancy in the USA means that one in five deaths nowadays is due to cancer, mostly diagnosed after symptoms set in. Among the common symptoms at presentation is unintentional weight loss, which has been associated with a higher risk of cancer diagnosis during the subsequent few months.

The current study was motivated by the fact that serial weight recordings have not been exploited to yield data on the association of weight loss with cancer and by the need to include all cancer diagnoses in a large group. Intention to lose weight must also be accounted for when attempting to quantify the association with cancer.

The study included females aged at least 40 years within the Nurses’ Health Study, followed up over 38 years, and males from the Health Professionals Follow-Up Study, also aged 40 years or more, monitored for 28 years. All participants were checked for weight change as determined by the weights recorded twice a year.

The researchers stratified weight change by intention to do so, considering changes in physical activity and diet quality. If both changed, high intentionality was attributed, with medium and low intentionality if only one or neither changed.

What did the study show?

The study included over 157,000 participants, with a median age of 62. Over 70% were female, and 95% were White. The follow-up covered a total of 1.64 million person-years (PY). About 5% of newly diagnosed cancer patients lost 10% of their body weight or more during the 12 months before their cancer diagnosis.

During this cumulative period, there were almost 16,000 new cancer diagnoses, at 964 per 100,000 PY. However, the incidence rate increased to 1,300 per 100,000 PY when limited to those diagnosed within 12 months of recent weight change, amounting to more than 10% of body weight. In contrast, among those who did not lose weight within the last 12 months, the incidence of cancer was ~870 per 100,000 PY.

Thus, there was an excess of nearly 500 cases per 100,000 PY among people who had recently lost 10% or more of their body weight.

When categorized by intentionality, those who lost this amount of weight in the last 12 months with low intentionality markers had a cancer incidence of nearly 2,300 per 100,000 PY, but only 1200 per 100,000 PY for those who did not lose weight. That is, there were almost 1,500 more cases of cancer newly diagnosed per 100,000 PY among those who lost weight without meaning to.

Cancers among people who lost weight were most likely to be in the upper gastrointestinal tract, that is, the esophagus, stomach, liver and biliary tract, and pancreas. These comprised 173 per 100,000 PY in the recent weight loss category but only 36 per 100,000 PY among the others. Thus, there was an excess of about 140 cases per 100,000 PY in the weight loss group.

These cancers continued to be identified at a higher rate among those with unintentional weight loss for the next two years.

Other cancers also showed similar patterns, with intergroup differences of 105, 80, and 63 cases per 100,000 PY for lung, blood, and colorectal cancers, respectively. The more the weight loss, the higher the incidence rate rose. There was no significant difference between the sexes or in the presence of other medical conditions.

Cancer incidence was also higher over the next six months among those who lost between 5% and 10% of body weight compared to those who did not lose weight. However, the extent of weight loss was not associated with the stage of cancer.

Weight loss and a history of smoking also predicted a higher cancer incidence rate than weight loss without a smoking history. Among people aged 60 years or more, over 3% of those who lost 10% or more of their body weight unintentionally would be diagnosed with cancer over the next 12 months. This strengthens the earlier recommendation that “individuals aged 60 years or older with unexplained weight loss should undergo evaluation for cancer.”  

Important exceptions to this pattern were cancers of the breast, urogenital tract, brain, and melanoma.

What are the implications?

“Health professionals with weight loss within the prior 2 years had a significantly higher risk of cancer during the subsequent 12 months compared with those without recent weight loss.” The most common type was upper gastrointestinal cancer in this group.