Does Weight Loss Help?
With all the evidence pointing to high BMI as a cancer risk factor, a logical conclusion is that weight loss should reduce that excess risk. However, Dr. Bea said, there’s actually little data to support that, and what exists comes from observational studies.
Some research has focused on people who had substantial weight loss after bariatric surgery, with encouraging results. A study published in JAMA found that among 5053 people who underwent bariatric surgery, 2.9% developed an obesity-related cancer over 10 years compared with 4.9% in the nonsurgery group.
Most people, however, aim for less dramatic weight loss, with the help of diet and exercise or sometimes medication. Some evidence shows that a modest degree of weight loss may lower the risks for postmenopausal breast and endometrial cancers.
A 2020 pooled analysis found, for instance, that among women aged ≥ 50 years, those who lost as little as 2.0-4.5 kg, or 4.4-10.0 pounds, and kept it off for 10 years had a lower risk for breast cancer than women whose weight remained stable. And losing more weight — 9 kg, or about 20 pounds, or more — was even better for lowering cancer risk.
But other research suggests the opposite. A recent analysis found that people who lost weight within the past 2 years through diet and exercise had a higher risk for a range of cancers compared with those who did not lose weight. Overall, though, the increased risk was quite low.
Whatever the research does, or doesn’t, show about weight and cancer risk, Dr. Basen-Engquist said, it’s important that risk factors, obesity and otherwise, aren’t “used as blame tools.”
“With obesity, behavior certainly plays into it,” she said. “But there are so many influences on our behavior that are socially determined.”
Both Dr. Basen-Engquist and Dr. Meyerhardt said it’s important for clinicians to consider the individual in front of them and for everyone to set realistic expectations.
People with obesity should not feel they have to become thin to be healthier, and no one has to leap from being sedentary to exercising several hours a week.
“We don’t want patients to feel that if they don’t get to a stated goal in a guideline, it’s all for naught,” Dr. Meyerhardt said.
A version of this article appeared on Medscape.com.