While the media often reports on foods that "prevent cancer" and we would love to be told that eating one particular food will prevent cancer, it is unlikely that such a food exists. It is more likely that a combination of good foods may have a preventive effect. Studies over the years have looked at our diets and what foods, if any, will lead to a lower risk of cancer. Fruits and vegetables, whole grains and unprocessed foods have all been promoted as reducing cancer risk. Unfortunately, studies have not consistently proven this to be true. Expert panels state that a diet high in fruits and vegetables "probably" reduces cancer risk, but we just don't know for sure.

However, a healthy diet plays an important role in a sort of "triangle" of cancer prevention. A healthy diet, combined with regular physical activity and maintaining a healthy weight has been shown to reduce cancer risk. This triangle is thought to be the second most important step, after not smoking, to preventing cancer.

While what we eat is probably linked to cancer development, being overweight and having a diet high in fat is clearly related to the development of certain cancer types. These include breast cancer (in post menopausal women), cancers of the colon, endometrium (uterus), esophagus and kidney. Evidence is highly suggestive that excess weight also increases the risk of cancers of the pancreas, gall bladder, thyroid, ovary, cervix and prostate, multiple myeloma and Hodgkin's lymphoma. Body weight is evaluated using body mass index or BMI, which is your body weight in kilograms divided by your height in meters, squared. Experts define a healthy BMI to be 18.5-25 kg/m², a BMI of 25-29.9 kg/m² to be overweight and a BMI over 30 kg/m² to be obese.

The third part of the triangle is physical activity, which studies have found can reduce the risk of cancers of the breast, colon, prostate and endometrium (uterine). How much activity are we talking about? Experts feel that somewhere between 30 and 60 minutes per day of "moderate to vigorous" activity is needed to impact cancer risk. A moderate activity is the equivalent of a brisk walk, whereas vigorous activities increase heart and breathing rates. Wonder how to get started with an exercise regimen? Make it fun and set reasonable goals. Find a friend to be a walking partner- you can motivate each other and make the walk more enjoyable. Vary the setting; try a park or public garden, use the mall when weather is bad, get creative and keep it interesting! Want to pick up the pace? Look into local gyms and workout groups, yoga, pilates and swim clubs or YMCAs. Start with an attainable goal- if you haven't ever exercised, a walk through the neighborhood is a start. Keep increasing your intensity (walk faster, carry weights) and/or distance over time. You may want to discuss your plans with your healthcare provider to be sure your exercise plan is safe for you. Get started by learning more at the American Cancer Society and LIVESTRONG.

As you can imagine, healthy weight, physical activity and a good diet are inter-related and one can often lead to another. If anything in your profile linked to the triangle is concerning, it will be discussed below.

Resources to learn more about how diet, physical activity and weight are related to cancer

A healthy diet, regular physical activity and maintaining a healthy weight have been linked to a lower risk of developing cancer. These three components make up the "cancer prevention triangle". They are strongly inter-related and working to improve one can often lead to improvements in another. Use the links below to learn more about this prevention triangle and ways to work towards a healthier you.

• Eat Healthy and Get Active at the American Cancer Society website.
• Reduce Your Cancer Risk at the American Institute for Cancer Research.
• American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention.
• Dietary Guidelines for Americans, 2010 from the USDA.
• The US Department of Health & Human Services 2008 Physical Activity Guidelines for Americans.
• NIH AARP Diet & Health Study: a study developed at the National Cancer Institute of the National Institutes of Health to improve our understanding of the relationship between diet and health.
• The European Prospective Investigation into Cancer & Nutrition (EPIC): A large study by the International Agency for Research on Cancer investigating the relationships between diet, nutritional status, lifestyle and environmental factors and the incidence of cancer and other chronic diseases.