Obesity and prostate cancer can be a dangerous combination. In 2004, researchers published a study that showed prostate cancer patients who were overweight had more recurrences after surgery.

A follow-up study this year by the same team—now at Cedars-Sinai—showed that the increased risk of recurrence also meant an increased risk of death from prostate cancer. Carrying extra weight doesn't necessarily cause prostate cancer, but it can make surviving the disease more difficult.

The message is clear to Dr. Stephen Freedland, director of the Cedars-Sinai Center for Integrated Research in Cancer and Lifestyle (CIRCL). "Patients often ask what they can do to combat their prostate cancers," he says. "The number one thing I talk to them about is weight loss. Among lifestyle factors, obesity is by far the strongest and clearest link to an aggressive and ultimately deadly course for this disease."

Dr. Freedland and his team are conducting new studies to better understand how losing weight impacts the growth of tumors. In one trial, prostate cancer patients are placed on a diet that's very low in sugar and carbohydrates, resulting in an average loss of 30 pounds in six months. "Our question is: Does that slow tumor growth?" Dr. Freedland says. "We're also looking at the metabolomics, or the chemical fingerprints of specific cellular processes, in obese people, nonobese people, patients who've gone on diets, and those who haven't."

While researchers at CIRCL study lifestyle factors such as exercise and cholesterol, the main therapeutic focus right now is encouraging patients to give up simple sugars. When we eat sugar, our body makes insulin—a growth factor for prostate cancer cells. Avoiding sugar and the resulting insulin spike also helps with weight loss. So it's a dietary change that can help on two fronts.

"But you have to know where sugars come from and eat nutritious meals," says Dr. Freedland. "Patients will tell me that they've given up red meat in favor of fish. Turns out, they are abstaining from grass-fed beef, which is reasonably healthy, and are now eating tilapia, which is anything but healthy. And they're eating fat-free ice cream, which is chock-full of sugar. We've been fat-phobic in the United States for 30 years. I wouldn't tell people to eat all the fat that they want. But when it comes to fighting obesity, sugar is public enemy number one."

That means avoiding the hidden sugars in white rice, pasta, and white bread. Giving up sodas is great, but it's not enough if you're still eating the sugars in carbohydrates such as french fries, cookies, and candy bars. "Even your basic baked potato has a lot of carbs," Dr. Freedland adds. "Many people can scale back on sugar at breakfast, lunch, and dinner, but when they want a snack, they grab that piece of candy. We encourage a handful of nuts or vegetables instead."

Exercise can not only help with weight loss, but may also be a variable in the cancer equation. Muscles initially absorb sugar, and researchers at CIRCL believe the additional muscle formation from exercise may help people better handle a slice of birthday cake and other sugary treats.

Dr. Freedland points out that exercise also promotes healthier blood flow. "Cancers tend to pop up in areas where nutrients are scarce and immune cells have less fuel to do their job. Without exercise and good blood flow, we create niche areas that can lead to cellular damage and cancers."

For prostate health, the data indicate that vigorous exercise is best. If you can hold a pleasant conversation while you're exercising, you probably aren't working hard enough. It doesn't matter if you swim, bike, jog, or speed walk. Even half an hour of walking stairs or doing the treadmill 3 days a week can add up. In fact, there is another active clinical trial at CIRCL looking at the benefits for late stage prostate cancer patients who exercise 3 times weekly.

Higher levels of cholesterol, estrogen, and inflammation also tie obesity to prostate cancer. Dr. Freedland believes we can improve our overall health with the right lifestyle choices. "It's too challenging for someone to eat this way for their heart and another way for their diabetes, and yet a third way for their prostate," Dr. Freedland says.

"The advice I give applies to all of that: avoid sugars and try to lose some weight. Focus on natural foods, like grass-fed beef, free-range chicken, wild-caught fish, vegetables, fruits, and nuts. Get exercise, don't smoke, and drink alcohol in moderation.

"That will help with numerous diseases and not just prostate cancer. Remember, genes load the gun, but lifestyle pulls the trigger."