The research adds to the reasons to shed some pounds
A new JAMA review concludes that excess body weight contributes to about 10% of new cancer diagnoses in the U.S. each year by triggering biological changes that promote tumor growth.
Researchers say chronic inflammation, hormone changes, immune system suppression, and alterations in the gut microbiome are among the key mechanisms linking obesity to cancer.
The review suggests losing more than 10% of body weight may help reduce obesity-related cancer risk, although preventing obesity remains the most effective strategy.
A new scientific review published in JAMA is shedding new light on why obesity substantially increases cancer risk, detailing the complex biological processes that allow excess body fat to create an environment where cancer can develop and thrive.
The review, authored by researchers from Memorial Sloan Kettering Cancer Center, the University of Kansas Cancer Center, and Emory University's Winship Cancer Institute, concludes that overweight and obesity account for roughly 10% of all new cancer diagnoses in the United States each year. The findings synthesize evidence from laboratory research, clinical trials, and large population studies.
The researchers say obesity is far more than an issue of excess weight. It represents a widespread disruption of normal metabolism that affects nearly every system in the body.
"When we think about obesity, we need to think beyond body size," said Dr. Kristy Brown, co-leader of the Obesity, Metabolic Health, and Cancer research program at the University of Kansas Cancer Center and a co-author of the review. "We have the epidemiological data, we have the mechanistic data, and we have the clinical data that show the impact of obesity on outcomes for patients."
How obesity promotes cancer
According to the review, obesity alters the body's fat tissue, causing it to become chronically inflamed. That inflammation produces chemical signals that can stimulate tumor growth, while weakening the immune system's ability to detect and destroy emerging cancer cells.
The researchers identified several key mechanisms behind the increased risk:
Persistent, low-grade inflammation that promotes tumor development.
Increased production of estrogen and other hormones that can fuel hormone-sensitive cancers.
Elevated insulin and altered metabolism that encourage cancer cell growth.
Oxidative stress that damages DNA.
Changes in the gut microbiome that may further promote inflammation and cancer development.
Suppression of immune cells that normally eliminate abnormal cells before they become cancerous.
These biological changes have been linked to at least 13 cancers, including colorectal, pancreatic, liver, kidney, ovarian, thyroid, and postmenopausal breast and endometrial cancers. The strongest associations are seen with endometrial and certain liver and biliary tract cancers.
Weight loss may reduce risk
The review also examined evidence on whether losing weight lowers cancer risk.
Observational studies involving patients who underwent bariatric surgery or used GLP-1 receptor agonist medications found modest reductions in obesity-related cancer incidence among people who lost more than 10% of their body weight. The authors caution that additional research is needed, but the findings suggest meaningful weight loss may help reverse some of the biological changes associated with obesity.
Researchers noted that preventing obesity in the first place is likely to provide the greatest benefit because some obesity-related biological changes become more difficult to reverse after years of excess weight.
A growing public health concern
The findings come as obesity rates continue to climb in the United States and worldwide. The review notes that nearly half of U.S. adults are projected to have obesity by 2030, while global obesity rates are also expected to rise sharply over the next decade. At the same time, cancer diagnoses are increasing worldwide, making obesity prevention an increasingly important component of cancer prevention efforts.
The authors conclude that addressing obesity should be viewed not only as a strategy for improving cardiovascular and metabolic health, but also as an important opportunity to reduce future cancer risk.
Posted: 2026-07-01 12:44:26

















