Dr. Johnston reviews a 2025 observational study of more than 86,000 matched adults with overweight or obesity, with and without diabetes. Cancer rates were lower among GLP-1 users, including 17% lower relative risk overall. He notes the study cannot prove GLP-1 drugs prevent cancer.
Could one of the biggest breakthroughs in weight loss treatment also prevent cancer?
We've known for decades obesity is not just cosmetic. It increases your risk of a host of diseases, including cancer. And your family history will tell you a lot about the kind of diseases you're at risk for in life. Both of my parents were overweight and both of them had diabetes. I don't want diabetes. It's one of the things that keeps me going to the gym.
>> I don't want to be fat. I don't want to be fat. I don't want to be fat.
>> In an analysis of the Framingham Heart Study, obesity at the age of 40 was associated with 6 to 7 years of life lost among non-smokers. The researchers concluded that these reductions in life expectancy were similar to that seen in tobacco smokers. Even being just 10 lbs overweight, that's not much according to America's standards, without even reaching the obesity category, was associated with three years fewer life among 40-year-old non-smokers.
Now, excess body fat has been linked to 13 different cancers. Colorectal, pancreatic, liver, kidney, ovarian, endometrial, and post-menopausal breast cancer are among them.
But now we have a new question. What happens when people with excess body weight take GLP-1 medications like semaglutide? When injectable semaglutide first came to the market, I prescribed it strictly for its approved use in diabetics. But substantial weight loss became a prominent finding in patients who also had obesity, as most type 2 diabetics did. So the manufacturer received FDA approval for chronic weight management.
A 2025 study looked at more than 86,000 matched adults that were overweight or obese, with and without diabetes. Across the 14 cancer type study, cancer occurred at a rate of 13.6 cases per 1,000 person-years among people taking GLP-1 drugs compared to 16.4 among those who weren't. That corresponded to a 17% lower relative risk across all cancers. But endometrial cancer specifically was 25% lower. Ovarian cancer was 47% lower and meningiomas 31% lower.
Now, this was an observational study. It doesn't prove by itself that GLP-1s prevent cancer. But obesity increases the risk of numerous cancers. GLP-1 drugs can produce substantial weight loss. And now we're seeing human evidence associating these medicines with lower cancer incidence. Shedding those pounds may help lower your cancer risk.
But here's the primary question in my mind. Would losing the same amount of weight by another method produce the same cancer reduction? Or do GLP-1 medications do something specific beyond helping people shed pounds?
In part two, we'll look at a study involving 1.65 million people. A comparison with bariatric surgery and laboratory findings offer a possible explanation for the increased cancer reduction seen with GLP-1 medications.
Here's the research. You decide.
Educational research summary, not medical advice. Talk with your oncologist and pharmacist before starting, stopping or changing any treatment or supplement.