Plant-based diet leads to weight loss—and potential reduced risk of recurrence | ASCO 2024

Background

Nearly 70% of adults in the United States are overweight or obese. Maintaining a healthy weight is an important part of overall health and cancer prevention. Obesity is now linked to 13 cancers. Experts expect to see that number grow.

Obesity causes metabolic instability that can lead to cancer. Not only are people with high body mass index (BMI) at higher risk, but some normal-weight people may be at higher risk too. Among normal-weight people, metabolic instability may be due to extra body fat (adiposity) or high amounts of insulin, sometimes related to type 2 diabetes.

Among people with breast cancer, excess weight has been linked to higher rates of recurrence and cancer-related death. While some people lose weight after being diagnosed with breast cancer, many gain weight. Sometimes weight gain is due to treatment, often in the first five years after diagnosis. Weight gain—especially over 10% of one’s body weight—increases risk of death from cancer or any cause among people with breast cancer. In contrast, exercise helps people with breast cancer feel better and stay healthier. A summary of multiple observational breast cancer studies found that exercise lowered the risk of death from breast cancer by 40%. Research on this topic is ongoing.

A whole foods plant-based diet is increasingly found to have many benefits for overall health and cancer-related health. Whole foods are a good source of fiber. Research shows that a plant-based diet may reduce the risk of many conditions, including breast cancer, high blood pressure, heart disease, diabetes, and depression. Whole foods include fruits, vegetables, whole grains, beans, and other foods that are not processed.

Results

The research showed that women who ate a plant-based diet and exercised lost 13% of their weight over six months compared to women in the control group who lost 5% of their weight over six months. Average fat loss was six kilograms in the study group compared with two kilograms for women in control group. These results point to a significant benefit to eating a plant-based diet for weight loss.

This phase II clinical trial was held at one U.S. cancer center. The study recruited 43 postmenopausal women with an average age of 57. All were taking aromatase inhibitor endocrine therapy. Participants had to have a body mass index (BMI) of at least 27 kg/m2 to be eligible for the study. Their average BMI was 34 kg/m2. In general, a BMI over 25 is considered overweight and a BMI over 30 is obese. You can learn more about how BMI is calculated at the Centers for Disease Control website.

Participants were randomly assigned to one of two groups: a study group and a control group. The study group received personalized nutrition coaching, plant-based meal delivery, and a structured exercise program. The control group received a home treadmill and monthly check-in calls. The study group’s goals were adjusted weekly based on their progress.

What does it mean for you?

Maintaining a healthy weight is important for potentially reducing the risk of breast cancer recurrence and for overall health. But losing weight can be challenging for many people. This study shows the benefit of a plant-based diet and exercise as one effective weight-loss strategy. A plant-based diet is not only helpful for weight loss, but it’s increasingly recommended for healthy eating in general. Exercise can help you feel better mentally and physically and stay healthier longer.

Talk with your healthcare team about any lifestyle changes you are considering. Ask if there are resources at your hospital, such as nutrition counseling or yoga classes, to help you get started.

Visit these pages to get additional support for healthy eating and exercise:

• The LBBC EatBeyond program, a free five-week texting program with information about breast cancer and nutrition, starting the week of August 12
• The LBBC BeACTive exercise series with your host Sami Mansfield, certified cancer exercise specialist
• Nutrition and exercise
• Healthy eating habits you can start right now