How Diet and Exercise Affect the Risk of Cancer

There are few things more devastating than a cancer diagnosis. Whether it’s something you’ve experienced or watched a loved one go through, it can teach us to be aware of and up to date on what risk factors might affect us. While cancer is a genetic disease that can afflict anyone of any age, it has a long list of risk factors. There are some that we already know a lot about, including family history, environmental and chemical exposures, sunlight, age, smoking, chronic inflammation, and more. But there are even more ways you might be putting yourself at risk without recognizing it. Our team of experts examined how two lesser-known factors — diet and exercise — affect your risk of developing cancer.

The current obesity and physical activity trends in the U.S. are concerning and trending worse. From 1990-2000 through 2017-March 2020, the prevalence of obesity in U.S. adults rose from 30.5% to 41.9%, with the rate of severe obesity increasing from 4.7% to 9.2% over the same period.1

The CDC reported that the prevalence of physical inactivity (those who said they don’t exercise outside of work) was 25.3% between 2017 and 2020. While this number might not seem very high, it’s just an average, and several states reported levels of physical inactivity above 30%. The obesity crisis, coupled with low physical activity among adults in America, is even more urgent due to the increased risk of cancer associated with poor diet and insufficient exercise.

Breast, prostate, lung, and colorectal (colon and rectum) cancers are projected to be among the leading cancers by the end of 2023.2 Diet and physical activity have an especially profound impact on these types of cancers (though it isn’t limited to them), meaning that as long as we struggle to move our bodies and keep a healthy weight, these rates may continue to go up. However, there are some ways that you might be able to change your eating habits and live a more active lifestyle to mitigate your risk of cancer.

It is difficult to state definitively whether one food increases or decreases the risk for cancer, and even more challenging to show that something causes cancer. However, it’s no secret that what we eat affects our cancer risk. Between 4% and 5% of all cancer cases are linked to having a poor diet.3 But what constitutes a poor diet, and which foods are best limited or avoided?

In October 2015, the World Health Organization named processed meat as a cause of colorectal cancer. Processed meat includes products such as:11

• Hotdogs
• Sausage
• Ham
• Bacon
• Pepperoni
• Jerky
• Corned beef

A large 500,000-person prospective cohort study in the United Kingdom in 2019 found that eating about 50g of processed meat per day was associated with a 19% increased relative risk for colorectal cancer. Additionally, eating an average of 75g of red meat per day — the equivalent of ⅓ of an 8oz steak — was associated with an 18% relative risk increase for colorectal cancer (raising absolute risk for colorectal cancer from 5% to around 6%).4 12 While the occasional hamburger or hotdog is fine, medical experts urge moderation and eating consciously when it comes to red and processed meat. Some protein alternatives to red and processed meats include beans (pulses), fish, and poultry.

While you might not always think of alcohol as a food, its carcinogenic properties meant it still made our list. One study suggests that every additional glass of alcohol you consume daily raises your risk of cancer anywhere from 4% to 25%, depending on the type of cancer.5 And while you might have heard that red wine has anti-cancer properties, there is not enough scientific evidence to support that claim.6 13 Liver cancer might be the obvious conclusion, but alcohol also impacts your risk of colorectal cancer, breast cancer, and stomach cancer. It’s thought to contribute to 3.3% of all cancer cases.5 And even light to moderate alcohol intake has been shown to increase your cancer risk, with the National Toxicology Program of the U.S. Department of Health and Human Services listing alcohol as a “known human carcinogen.”14 15 16

It’s simply not enough to avoid certain foods. We should also look at how much we eat every day. Overeating can lead to becoming overweight or obese, a known risk factor for cancer.17 Excess body weight is linked to 5% of cancer diagnoses in men and 11% in women. However, there is an increased risk of developing certain cancers over others. 60% of uterine corpus cancers are attributed to excess body weight, compared to 4% of ovarian cancer diagnoses.3

The NIH claims that people who have severe obesity (a BMI over 35) are seven times more likely to develop endometrial cancers, while people who have overweight or obesity are two to four times more likely to develop it. Plus, individuals with obesity are more likely to suffer from other ailments — such as diabetes, chronic inflammation, and hormonal imbalances — that can further increase their risk of cancer.7

To see if you’re at a healthy weight, consider calculating your body mass index (BMI). Your BMI is a rough score calculated using your current height and weight that can help you start to determine whether or not your body is under- or overweight. If there’s room for improvement, try watching your portion sizes at meal and snack times, and consider limiting high-calorie foods, such as sugary drinks and highly processed snack foods. That said, BMI isn’t the end-all-be-all determining factor of your health. It doesn’t take into account things like your muscles or physical frame. Talk to your doctor if you’re concerned about your weight's impact on your health or if you feel like your BMI might not be an accurate reflection.

Doctors and nutritionists have always encouraged “eating the rainbow.” Eating a variety of vegetables and fruits and limiting alcohol, sugar, and processed meat is one way to get a wide variety of essential nutrients while limiting potential health problems (including increased cancer risk).8 A healthy diet with a low risk of cancer doesn’t have to feel limiting or dull, though.

The Mediterranean diet is one example of an eating pattern that may reduce the risk of cancer.18 An average Mediterranean diet contains:19

• Fresh vegetables (particularly cruciferous veggies, such as broccoli, cabbage, and brussels sprouts)
• Fresh fruits
• Legumes (such as beans, peas, and lentils)
• Whole grains
• Nuts and seeds
• Healthy fats such as olive oil
• Moderate amounts of dairy
• Low to moderate consumption of alcohol
• Limited red and processed meat
• Limited sugar intake
• Moderate amounts of fish, poultry, and eggs

Due to its antioxidant-rich and anti-inflammatory attributes, researchers think that Mediterranean diets are protective against cancer, particularly breast, colorectal, prostate, and lung cancers. Still, more research is needed to reach conclusive results.8

Your diet doesn’t have to be Mediterranean to be considered healthy, but it should still include many of the same elements. Eating a wide range of fruits, vegetables, whole grains, and healthy fats while limiting your alcohol, meat, and sugar intake is always your best bet.

A reported 3% of cancer diagnoses are attributed to a physically inactive lifestyle, but doctors suspect it might be more.3 Regular exercise has a tremendous impact on the body and an equally massive impact on the risk for certain cancers, which could be why it’s one of the more common recommendations for cancer prevention.23 It also plays an important role in how well cancer therapies work (and how many side effects you feel) both during and after treatment.3

Regular exercise decreases the risk of many cancers, such as:3 23

• Colon
• Endometrium
• Breast
• Stomach
• Bladder
• Esophagus
• Kidney

You don’t have to start running marathons to be healthier, either. Even moderate exercise reduces the risk of cancer mortality and eases the sometimes brutal effects of cancer therapies.3 Exercise has also been shown to decrease the risk of cancer relapse and has been attributed to better patient survival rates.9

Exercise is an effective prevention tool for all areas of your health. One of the many reasons behind this is that it can combat chronic inflammation, balance hormone levels, and improve bone density, as well as lower the risk of cancer while giving your body the strength it needs to recover or fight it.9

The CDC currently recommends 150 minutes of physical activity a week for adults and 60 minutes a day for children. It may sound like a lot, but exercise can literally be a walk in the park. Incorporating more movement into your daily regimen can lower your cancer risk, improve your mood, reduce stress, and boost your general well-being.10 20

Not sure where to begin? You can use technology to your advantage. A fitness tracker can help you start monitoring your baseline activity levels, and then you can use that as a platform for improvement. Focus on walking for one to five minutes daily in the beginning, then try branching out and trying something new. You may like walking around your neighborhood, or you could find that skiing or roller-skating is more your speed. It doesn’t matter what it looks like, but the more movement you incorporate, the better the health benefits.

While nutrition plays a significant role in our general health, it is essential to remember that the link between food and cancer is continually being studied and researched. We don’t completely understand how cancer works or how our lifestyles impact it. A few foods are proven to increase your cancer risks, such as alcohol and processed meat, and there are a few foods proven to help decrease your odds of developing cancer. But there’s no way to calculate your health solely based on your dietary choices.

The key takeaway is not to consider the elements of the diet by themselves but as a whole. Focusing on eating a well-balanced diet composed of fresh fruits, vegetables, healthy fats, and proteins is far better than simply avoiding specific foods and will be more sustainable for you to keep up in the long run.

Although intriguing and inspiring, the research on exercise is also still preliminary. More research needs to be done on the protective effects of exercise on cancer.

While not a food, we wanted to mention tobacco as it is an insidious habit that can disrupt and sabotage the most well-intentioned diets and exercise regimens. Considering that finishing meals and drinking alcohol can be pattern triggers for those who smoke, it’s important to remember that tobacco remains a leading cause of preventable disease, disability, and death, including deaths from cancer.21 22 Whether for chewing or smoking, this famous carcinogen is linked to the following types of cancers:22

There is no such thing as smoking responsibly or in moderation. Doctors, scientists, and nutritionists alike strongly urge against using tobacco in any amount or form.

Cancer is a life-changing diagnosis. However, there is much you can do to lower your risk, especially if you know you’re already genetically predisposed to certain kinds of cancer. Begin by moving more, limiting your red and processed meats, and avoiding carcinogens such as alcohol and tobacco. Plus, you can encourage family, friends, and coworkers to join you in making healthier choices at home, work, and while you’re out and about for community support and to help the health of those you love.