For people with overweight or obesity who have type 2 diabetes, a reduction in body mass as small as 7%—or 10.5 pounds for a 150-pound person—can help control the disease.

Now, evidence suggests that the same intensive diet and exercise plan that promotes such weight loss is also effective at reducing obesity-related cancer incidence, according to the results of a new study conducted by Johns Hopkins University researchers published in the journal Obesity.

Overweight and obesity have been found to increase the likelihood of developing 13 different types of cancer, including colorectal, esophageal, pancreatic and kidney cancers. But before now, proof that weight loss by itself could reduce cancer risk was scant.

By examining data from the Look AHEAD (Action for Health in Diabetes) clinical trial, the researchers compared the efficacy of an Intensive Lifestyle Intervention (ILI) treatment with a standard Diabetes Support and Education (DSE) treatment in decreasing cancer rates in overweight or obese people with type 2 diabetes and no prior history of nonmelanoma cancer. Between 2001 and 2004, 4,859 people matching the above description were randomly assigned to participate in either an ILI or DSE program.

The ILI curriculum encouraged participants to lose at least 7% of their body weight by eating only 1,200 to 1,800 calories per day and engaging in 175 or more minutes of moderate-intensity physical activity per week. In contrast, the DSE curriculum provided emotional support and education about diabetes to help participants manage their condition.

Following up an average of 11 years later, the researchers found that 332 participants in the ILI program and 352 participants in the DSE program—684 participants in total—had been diagnosed with some form of cancer. When they looked specifically at cancers associated with obesity, they found that participation in the ILI program was linked to a 16% decreased incidence. 

Although the exact mechanism by which obesity increases cancer risk isn’t known, one hypothesis points to systemic inflammation resulting from visceral fat buildup, also known as belly fat.

In an Obesity Society press release, Tiffany L. Carson, PhD, MPH, an assistant professor in the University of Alabama at Birmingham’s division of preventive medicine who was not involved in the research, said, “This analysis of Look AHEAD data is an important contribution, as it is one of the first studies to provide empirical data to suggest that a weight loss–focused lifestyle intervention can help to lower risk of obesity-related cancers.” (The study was underpowered to provide conclusive statistical evidence.)

Corresponding study author Hsin-Chieh “Jessica” Yeh, PhD, an associate professor in Johns Hopkins University’s division of general internal medicine, said the results demonstrate the importance of eating healthy and exercising regularly as a means of reducing cancer risk.

"Health care providers should be encouraged to provide such counseling or refer patients with obesity to intervention programs that help people manage their weight,” she said. “Moreover, establishing an environment with easier access to healthy food and physical activities is the foundation of obesity and cancer prevention.”

To learn more about the relationship between obesity and cancer risk, click here. To read about specific circumstances under which weight loss could be a sign of pancreatic cancer, click here.