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Researchers say people with obesity who are considered metabolically healthy still face higher cancer risks. EMS-FORSTER-PRODUCTIONS/Getty Images
  • Obesity is an established risk factor for a number of weight-related cancers.
  • New research shows that both metabolically healthy and unhealthy forms of obesity are associated with an increased risk of obesity-related cancers.
  • Experts say the study highlights the need to treat conditions such as high blood pressure and high blood sugar levels in people with obesity.

Metabolically healthy and unhealthy forms of obesity are both associated with an increased risk of various obesity-related cancers.

That’s according to an article published in the Journal of the National Cancer Institute.

Researchers looked at the medical records of 797,193 European individuals. They calculated an individual’s metabolic score that comprised blood pressure, plasma glucose, and triglycerides to provide a measure of healthy or unhealthy metabolic status and determined the relative risk for overall and site-specific cancers. Comparisons were made with metabolically healthy people of normal weight.

Combining different metabolic scores and BMIs, the researchers divided the participants into six categories based on their health status:

  • Metabolically unhealthy obesity – (nearly 7% of participants)
  • Metabolically healthy obesity – (3% of participants)
  • Metabolically unhealthy overweight – (15% of participants)
  • Metabolically healthy overweight – (nearly 20% of participants)
  • Metabolically unhealthy average weight – (12% of participants)
  • Metabolically healthy average weight – (42% of participants)

Some of the scientists’ findings included:

  • Metabolically unhealthy obesity compared to metabolically healthy normal weight was associated with an increased risk of obesity-related cancers, such as colon, rectal, pancreatic, endometrial, liver, gallbladder, and renal cell cancer. The highest risk was for endometrial, liver, and renal cell cancer.
  • Metabolically unhealthy women with obesity, had a 21% increased risk of colon cancer, were three times more likely to have endometrial cancer, and were 2.4 times more likely to develop kidney cancer compared to metabolically healthy women with normal weight.
  • Even metabolically healthy women with obesity had 2.4 times increased risk of endometrial cancer and a 77% increased risk of kidney cancer. However, there was no significant increase in the risk of colon cancer.
  • Metabolically unhealthy men with obesity, compared to metabolically healthy men of average weight, had 2.6 times the risk of kidney cancer, an 85% higher risk of colon cancer, and a 32% higher risk of both pancreatic and rectal cancer. Metabolically healthy men with obesity had a 67% increased risk of kidney cancer and a 42% increased risk of colon cancer, but there was no significant relationship with pancreatic or rectal cancer.

The scientists noted one unusual finding.

Both metabolically healthy and unhealthy men who were overweight had about a 50% increased risk of multiple myeloma, a blood cancer. Neither metabolically healthy nor unhealthy men with obesity had an increased risk of this cancer.

Metabolically healthy obesity often leads to metabolically unhealthy obesity, so early weight control measures are essential, the researchers said.

“Overall, this study highlights the importance of metabolic abnormalities in addition to obesity for increase in risk of obesity-related cancers,” said Dr. Rohan Garje, the chief of Genitourinary Medical Oncology at Miami Cancer Institute, part of Baptist Health in Florida who was not involved in the study.

“They observed an increased risk of cancers in metabolically unhealthy obese when compared to metabolically healthy normal weight. Metabolically healthy obesity also had increased risk of cancers, but the risk relationships were weaker,” Garje told Medical News Today.

“However, we must be cognizant about the limitations of the study as it was one-time assessment of metabolic abnormalities,” he added. “It’s important to understand that these categories are not fixed and can change over time. Metabolically healthy obesity can progress to metabolically unhealthy obesity as individuals age or develop additional risk factors, such as a sedentary lifestyle, poor diet, or genetic predispositions. Additionally, there are additional other factors that predispose someone to cancer, such as dietary patterns, medications, genetics, environmental exposures, and other health comorbidities which were not considered. Smoking history was accounted for in the study.”

“This study reminds us that all obese patients are not the same,” said Dr. Anton Bilchik, a surgical oncologist and division chair of general surgery at Providence Saint John’s Health Center and chief of medicine and director of the Gastrointestinal and Hepatobiliary Program at Saint John’s Cancer Institute in California who was not involved in the study.

“It was a large population study with a long follow-up. It is a unique study that divided the participants into healthy or unhealthy and found that they have a disproportionally high risk of cancer if they are unhealthy,” he told Medical News Today.

“This study provides newer data regarding the increased association of risk of cancers with metabolically unhealthy obesity,” Garje said. “It provides evidence to strongly support the need to address high blood pressure, abnormal lipid levels, and elevated blood sugar levels.”

Metabolic syndrome is a group of conditions that raise the risk of coronary heart disease, diabetes, stroke, and other serious health problems, according to the National Heart, Lung, and Blood Institute.

According to the new study, it might also cause cancer in some people.

“Although many think cancer arises secondary to poor luck and genetic mutation, it is, in fact, a disease of Western civilization,” says Dr. Mitchel Roslin, the chief of bariatric surgery at Lenox Hill Hospital in New York.

“In contrast, many believe that obesity results from an unhealthy lifestyle. This article demonstrates that obesity and metabolic dysfunction are strongly associated with an increased risk of many common, deadly tumors. The importance of these findings cannot be understated,” he told Medical News Today.

“Unfortunately, metabolic dysfunction is rarely treated unless there is clear evidence of diabetes, hyperlipidemia, or hypertension,” Roslin added. “However, metabolic aberrations start many years before these conditions are apparent. Most often, it begins with an increased level of insulin being produced to control blood sugar. As insulin promotes growth, when it is elevated, an ideal environment for tumor growth is created. Insulin also promotes increased fat storage. Increased fat burden or adiposity also changes key hormonal levels. In females, high insulin can block the conversion of testosterone to estrogen. In others, peripheral fat cells can cause an increased estrogen level, which has been linked to uterine cancer. The net result is that obesity and metabolic dysfunction can increase the likelihood of cancer sixfold.”