Obesity and cancer: How to decrease your risk


Obesity is directly linked to many cancers, but exercising can help you lose weight and reduce your risk.

Food is so readily abundant in the United States that most Americans can’t not eat. Restaurant portions are double what they should be – and let’s face it – we love to eat.

I was overweight most of my childhood. My parents grew up in the Great Depression, and as a kid, I couldn’t leave the table until I’d cleaned my plate. I got used to eating what was in front of me. I really love to eat, so I was “the chubby kid” all the way through high school.

Being overweight affects your self-image, but as an oncologist I’ve learned it can have a far more devastating effect on your health. Being obese increases your risk of developing cancer.

How does my weight affect my cancer risk?

There is significant data showing that people who are obese have higher rates of many types of cancer, including colon cancer and breast cancer.

Researchers have found that as your weight increases, your insulin levels also increase. This may be why obese patients have a higher risk of developing colon cancer and also a higher likelihood that their colon cancer will come back.

In addition, obese patients have a substantially higher risk of breast cancer and recurrence. This is likely because obese patients have much higher estrogen levels. Fat cells convert cholesterol molecules to estrogen, and the additional estrogen causes a hormonal imbalance. In fact, estrogen drives two-thirds of the breast cancer we see in postmenopausal patients.

To determine if you are obese, you will need to calculate your body mass index (BMI). It takes only a couple seconds using an online calculator. Anyone with a BMI of 30 or higher is considered obese.

Can you lose weight by simply cutting calories?

Our earliest ancestors were hunters and gatherers. They feasted for two or three days after a successful hunt or forage but would often go as long as a week without eating again. Their “feast or famine” lifestyle is programmed into our DNA – our bodies store every excess calorie we eat.

When we start to pack on the pounds, it can be very difficult to reverse. Your first thought may be to significantly cut your calories. That will help, but the human body cannot lose a significant amount of weight without adding aerobic exercise to the mix.

When you cut back your food intake, you will lose some weight in the beginning. However, if you don’t exercise, the weight loss will stop quickly. Your “caveman” instincts will kick in, and your body will slow down your metabolic rate. That means you’ll burn fewer calories, and you’ll be right back where you started – taking in more calories than you burn.

Simply put, to lose weight you have to burn more calories than you consume. The only way to do that is to eat a healthy diet and exercise. Your metabolism will stay revved up, and you’ll burn more calories throughout the day.

How do I start exercising?

I tell people who aren’t currently following an exercise plan to start with walking. On your first day, walk 10 or 15 minutes. Every week, add a few minutes to your walk. Your ultimate goal should be to walk 35 to 40 minutes at a brisk pace, five days each week. I advise beginner exercisers to ease into a routine so they don’t wind up with injuries.

Consider using a fitness tracker (I use Runkeeper) to keep track of how far you walk each day. Mobile apps make it easy to store your workout data and share it with your physician.

Cancer patients who exercise regularly experience less fatigue and lose less weight during chemotherapy than those who do not. Exercise maintains flexibility and muscle strength, which can decrease during cancer treatment. Another bonus is that exercise increases endorphins, which can help elevate your mood – a powerful resource when you’re fighting cancer.

I know eating a healthy diet and exercising is easier said than done. Habits are hard to break – I’ve been there. Over time, I had to learn that I don’t have to clean my plate and that I have to exercise to stay healthy.

If you would like to speak to a UT Southwestern dietitian or physician about the benefits of exercise and a healthy diet, request an appointment. With dedication and perseverance, you can get healthier and build a strong defense against cancer.