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(CNN) -- No one wants to get cancer. Turns out, you have considerable power over that scary fate. True, it's possible to do everything "right" and still end up developing the disease.

But a surprising amount of cancer is preventable -- in fact, a stunning one-half to two-thirds of our risk is in our control, many experts now believe. For example, about a third of all cancer deaths in the United States each year are linked to diet and physical inactivity.

Cervical cancer, which is linked to human papillomavirus, (HPV) can be avoided with vaccination.

"A proper diet, exercise, stress management and social support could go a long way toward addressing the vast majority of health problems" -- including cancer, says Dr. Brent Bauer, director of the Complementary and Integrative Medicine program at the Mayo Clinic. It just comes down to adopting -- and sticking to -- some simple habits.

Eat right

Load up on antioxidant-packed superfoods, like blueberries and kale, to keep cancer away, right? Yes, fruits and veggies are a crucial part of a healthy diet (and antioxidants do seem to thwart tumors, at least in lab studies -- see "Anticancer Foods," right).

But in recent years a more sophisticated understanding of how food affects our cancer risk has emerged.

Translation: We should be focusing not just on what we eat, but on how much. Obesity is a key culprit in a number of diseases, from diabetes to heart conditions, and it might contribute to cancer as well, in different ways.

After menopause, for instance, extra pounds can keep estrogen levels high, which can push breast cells to divide more aggressively, in some cases leading to tumors.

Two small changes that help you stay in shape and may lower your cancer risk: First, eat more fruits and vegetables -- any kind, but especially brightly colored ones, which are high in antioxidants. Consuming at least five servings a day can significantly lower your chances of getting cancer, Doyle says.

Second, have less red meat and more plant-based proteins such as beans and tofu. Cooking red meat at high temperatures releases compounds that, when digested, have been linked to some cancers.

"The good news," Doyle notes, "is you don't have to change absolutely every single thing to see a real difference in your risk."

Squeeze in exercise

Doctors are increasingly aware that being physically active goes hand in hand with eating well when it comes to preventing cancer.

Investing in a healthy diet but not getting enough exercise could negate the benefits of all that responsible eating; working out fanatically but overdoing it on high-calorie favorites won't do your body much good, either.

Some studies have linked higher levels of physical activity with lower levels of breast cancer, although the reason for the association isn't exactly clear. (Exercise might adjust your hormonal balance to make it less hospitable for tumors to grow, or trigger metabolic changes that make cancer less likely.)

How much is enough?

Though there's no specific anticancer formula for exercise, (yet) the ACS recommends 150 minutes a week of moderate physical activity -- walking briskly, gardening, playing tennis, whatever you like.

Manage stress

Constant stress over months and years may drive the body's systems to extremes -- contributing to an increased risk for heart disease and even a weakened immune system, which can create fertile ground for tumors, experts believe.

While no studies directly connect stress to your cancer risk, a link isn't unrealistic: Lab and animal research has shown that hormones released in response to stress can actually help a tumor grow -- they may promote the formation of blood vessels that tumors need to survive.

So minimizing stress might help ward off cancer. One simple way to start: As soon as you wake up, think about five things that make you happy and why they do, says Dr. Amit Sood, chair of the Mayo Clinic Mind Body Initiative.

That keeps your brain from falling into worry mode, and staying there for the rest of the day. "Think of cancer as a weed," Sood says. "We change the soil so the weed doesn't grow. "

Get enough sleep

While we slumber, both our body and brain are hard at work, repairing tissues and tuning up neural connections. People who skimp on the eight to nine hours that the average adult needs tend to have higher rates of heart disease, diabetes -- and possibly cancer.

In a large study of Japanese women, those who slept less than six hours a night over several years were more likely to develop breast cancer (though that might have been due to family history or other factors for which researchers didn't control).

Another study that did control for family history, published in the journal Cancer, found that people who slept that little were almost 50 percent more likely than subjects who got seven hours or more of rest to grow colorectal adenomas -- precursors to colon cancer.

Why?

Being deprived of the sleep hormone melatonin might be the cause. Normally, melatonin levels in your body peak at night, triggered by the absence of light, and drop during the day. But when production of the hormone is interrupted, it can have serious effects: Recent findings from a long-term study revealed that nurses who were on call more frequently at night had higher rates of breast cancer than those who worked days.

That doesn't mean you will absolutely develop cancer if you work nights or if you can't always snag a solid seven hours of shut-eye -- just that your overall risk might be higher. But the research does suggest that it's beneficial to keep melatonin flowing -- say, by lying in the dark instead of turning on the lights if you wake up in the wee hours. It also tells us that getting a good night's sleep should be a top priority.

That's one doctor's order we're happy to take.

Copyright Health Magazine 2011

SOURCE: http://www.cnn.com/2013/11/22/health/fighting-off-cancer/index.html?hpt=he_c1