Many studies show convincing evidence that there is a strong link between excess body fat and cancer risk. The mechanism of how excess body fat increases cancer is complex but known to be related to hormones. Animal studies show a positive association with certain cancers — specifically breast and endometrial cancers — due to an increase in the production of ovarian steroid hormones, particularly estrogen that results from an excess in energy intake.

The size of a person’s waist can also predict the risk of chronic diseases. For example, metabolic syndrome is associated with increased waist size and can lead to diabetes and cardiovascular disease, which can lead to increased incidences of certain types of cancer like breast cancer.

An increase in weight can influence several hormone systems, as well, such as insulin and the body’s response to inflammation, both of which play a role in the development of cancer.

Excess weight can lead to increased insulin resistance, in which the body increases circulating insulin because cells don’t recognize it. As people become overweight and their bodies become insulin-resistant and insulin production rises, the amount of estrogen circulating in the body increases, too. This estrogen has been shown to decrease normal cell death (apoptosis) and increase cell proliferation — all hallmarks of cancer. Increased insulin circulating in the body compounded with obesity have the potential to lead to increased prevalence of breast cancer.

Carrying around excess weight can also produce cell-signaling proteins called cytokines. Cytokines can increase inflammation in our bodies and create a state of low-grade inflammation, leading to the progression and development of cancer.

Maintaining a healthy weight throughout your life

Our food choices can play a huge role in maintaining a healthy weight. We recommend a plant-based eating pattern that includes the rainbow of color, whole grains, and legumes four to six days of the week.

Here are some tips on how to incorporate more whole foods into your life. These tips can help you to increase the nutrient content of your overall diet so you can take the steps to help reduce your risk of cancer.

• Start small and build up gradually. Rome wasn’t built in a day and you can’t expect dramatic, sustainable changes overnight.
• Start by setting a goal to cook three meals per week that are whole-foods-based and grow from there. Alternatively, choose one day a week to eat plant-based and slowly add more plant-based days as you feel comfortable until you’ve consistently reached this dietary pattern four to six days of the week.
• Consume the “rainbow of color” throughout the day and vary your food color choices with each meal. Aim to eat fruits, vegetables, whole grains, and legumes from each color of the rainbow each day with the long-term goal of four to six days of the week.
• Make at least half your grains whole grains. Start easy – you can mix half whole grains with refined grains (think half brown rice with white rice) until you are used to the flavor profile of whole grains. Be patient with yourself, transitions can take time!
• Find ways to eat more plant-based protein sources including legumes (e.g., beans, peas, lentils), nuts, seeds, and whole forms of soy foods like soy milk, tofu, tempeh, and edamame. Aim for one day a week where your meals are vegetarian.
• Use healthy oils such as olive oil for most of your cooking needs. Be sure to use a neutral-tasting, heat-resistant oil such as sunflower or canola oil when cooking with high heat.
• When plating your meal, consider filling up two-thirds of your plate with plant foods and one-third of your plate with animal-based foods. Consume animal foods in moderation, including seafood, lean meats, and eggs. Animal-based foods can be thought of as condiments and not necessarily the main attraction of a meal.

Kate Ueland, MS, RD, specializes in oncology nutrition, primarily working with individuals who have breast, ovarian, renal, and melanoma cancers throughout all stages of their cancer journey at Seattle Cancer Care Alliance (SCCA) in Seattle, WA. As Cook for Your Life’s nutrition advisor and editor, Kate ensures all culinary content adheres to the Academy of Nutrition and Dietetics and follows science-based guidelines.