It’s estimated one out of every three cancers in the United States are linked to excess body weight, poor nutrition, or physical inactivity. Since being overweight seems to have the strongest evidence linking it to cancer and the risk of recurrence, it is important to maintain an ideal body weight. Excess weight may influence your cancer risk by affecting:
- How your body processes fats and sugars
- How your immune system functions
- Your levels of certain hormones, such as insulin and estrogen
- Factors that regulate cell division
- Proteins that influence how your body uses certain hormones
It is especially important for breast cancer patients to maintain an ideal body weight since extra body fat can encourage estrogen production, which in turn can trigger breast cancer cell growth. This higher risk is because fat cells make estrogen; extra fat cells mean more estrogen in the body and estrogen can make hormone-receptor-positive breast cancers develop and grow.
Most estrogens in the body are produced in the ovaries in premenopausal women. In postmenopausal women who no longer produce much estrogen, estrogens primarily come from their fat tissue. Fat tissue contains an enzyme called aromatase that converts hormones called androgens to estrogens.
Overweight women have higher blood estrogen levels than leaner women. Some of the increased breast cancer risk among postmenopausal women comes from this extra estrogen. Women who are heavier also tend to have higher levels of insulin in their bodies compared to leaner women. Some studies have shown an increased risk of breast cancer among postmenopausal women with high levels of insulin including women with type 2 diabetes. The findings on a possible link between insulin levels and breast cancer risk are less clear among premenopausal women.
How Much Should You Weigh?
Your body weight consists of lean mass (bones, muscles, tissues, fluids and organs) and fat mass. You need both. However, too much body fat can increase your risk for health problems such as heart disease, diabetes, and cancer. Too little body fat has been associated with malnutrition and osteoporosis.
Cancer treatments often affect your weight. You may not see a change on the scale; however you may have had muscle loss and fat gain due to your treatments. Having your body fat measurements taken can help you determine an ideal body weight.
One way to determine your ideal weight is by using a body mass index (BMI). The BMI is a number based on your weight and height. In general, the higher the number, the more body fat you have. Find one from the Centers for Disease Control HERE.
Measuring Your Body Fat
Although BMI gives you a good estimate of total body fat, it doesn’t work well for everybody. It may not be accurate for people with greater muscle mass (such as athletes) or in people who may have lost muscle mass due to aging or illness. A good way to help determine your ideal weight is to have your body fat measured. This method involves measuring the thickness of your skin folds to help determine how much fat mass you have. Ask your doctors or exercise specialist where you can have this test performed.
Managing Your Weight through Exercise
Regular aerobic exercise and resistance training are two of the best ways to help you maintain an ideal weight. Aerobic exercise, sometimes called cardio, is designed to strengthen your heart and lungs, improve your endurance and elevate your metabolism. Any activity that raises your heart rate and keeps it elevated for prolonged periods of time is considered aerobic.
What may be considered a low- or moderate-intensity activity for a healthy person may seem like a high-intensity activity for someone with cancer. This is especially true if you are new to exercise. Ask your doctor what intensity level they want you to work at.
Some guidelines to follow are:
- Start out slowly, a few minutes at a time and gradually build up to 30 minutes on continued activity.
- Be careful if you are taking blood pressure medication that controls your heart rate. Your heart rate will not go up, but your blood pressure can get high.
- If balance is an issue, avoid uneven surfaces.
- Avoid swimming if you have a catheter or skin sensitivity from radiation.
- Avoid high impact activity if at risk for fracture.
Resistance training helps you build and maintain your lean mass and decrease your risks of osteoporosis. Make sure you have full range of motion in the area you are working. Always start with a light weight, gradually increasing your resistance.
Some special considerations for cancer patients:
- Know the signs of lymphedema, when to stop and what to report immediately.
- Do not use heavy weights or do exercise that puts too much stress on your bones if you have:
- Cancer that has spread to the bone
- Nerve damage (neuropathy)
- Poor vision
- Poor balance, or weakness.
- Do not use resistance training programs in areas where you do not have 90% of your pre-treatment ROM.
- Avoid heavy lifting which can dislodge your port if you have one.
- Start out with light weights; wait 24 hour to assess swelling, before increasing weight loads.
The good news is physical activity not only helps prevent and reverse weight gain, it also helps lower your risk of heart disease, diabetes, and some types of cancer recurrence. Time to get moving!