Cancer is the second most common cause of death in the United States according to the National Cancer Institute (NCI). Heart disease is the first. But while most people know about ways to prevent heart disease — eating less saturated fat, getting more exercise, lowering cholesterol levels — they aren't necessarily thinking about how to prevent cancer. And that's a shame, because according to the American Institute for Cancer Research, nearly half of the most common types of cancer can be prevented.

The right habits are critical. For example, up to one third of cancer cases in the United States are related to excess weight or obesity, physical inactivity and/or poor nutrition, according to a new report from NCI.

Experts say controlling these six lifestyle and health factors is key to staying cancer free.

Related: 6 Powerful Ways to Reduce Your Cancer Risk

Diet

Eating more of some foods and less of others can help prevent cancer. David Khayat, MD, PhD, head of medical oncology at the Pitié-Salpêtrière Hospital in Paris, wrote a book on the topic. In "The Anti-Cancer Diet: Reduce Cancer Risk Through the Foods You Eat,” he lists seven important cancer-fighting foods everyone would benefit from eating regularly:

  • Pomegranate
  • Turmeric
  • Green tea
  • Broccoli
  • Selenium-rich foods such as Brazil nuts and oysters
  • Quercetin-rich foods such as capers and onions, and garlic

Related: The Anti-Cancer Diet

The Physician's Committee for Responsible Medicine says what "while more research is needed in this area," these dietary strategies may reduce cancer risk:

  • Avoid dairy products to cut prostate cancer risk.
  • Limit or avoid alcohol to reduce the risk of cancers of the mouth, pharynx, larynx, esophagus, colon, rectum and breast.
  • Avoid red and processed meat to reduce the risk of cancers of the colon and rectum.
  • Avoid grilled, fried and broiled meats to reduce the risk of cancers of the colon, rectum, breast, prostate, kidney and pancreas.
  • Women should consume soy products in adolescence to reduce breast cancer risk. Breast cancer survivors should consume soy products to reduce risk of cancer recurrence and overall mortality.
  • Eat a diet rich in fruits and vegetables to reduce risk of several forms of cancer.

Weight

If you're flabby around the middle, changing that spare tire for a leaner waist by losing weight could lower your risk for fatal cancers by 20 percent, according to the American Cancer Society (ACS). Excess weight and belly fat are linked with cancers of the colon, esophagus, kidneys, pancreas, uterus and breast (in post-menopausal women), says the ACS.

Activity level

According to the National Cancer Institute, regular exercise has been linked in numerous studies to a reduced risk of several types of cancer: colon, breast, endometrial, lung and prostate. The ACS says walking for a half hour a day is enough to help keep cancer at bay

Related: Can't Get Into the Exercise Habit? Try this Trick

Sun exposure

Showing as little skin as possible on sunny days is one way to prevent skin cancer, but it's not enough. It's important to wear sunscreen even on overcast days and to make sure you're covering every exposed inch of your body, including tops of feet, bald spots and other frequently missed spots.

Related: Worried about Skin Cancer? Count the Moles on Your Right Arm

Vaccinations

One of a young person's best shots (no pun intended) against developing cancer of the cervix, penis, anus, vulva, vagina or throat is a simple vaccine that provides protection from the human papilloma virus (HPV). Almost 100 percent of sexually active adults will have an HPV infection at some point, according to the Centers for Disease Control and Prevention (CDC), but the vaccine is effective only if given before a person has sex. The CDC recommends most kids get the HPV vaccine around age 11 or 12. Parents: Talk to your pediatrician about what's best for your child.

Related: 9 Things You Should Know About the HPV Vaccine

Smoking

If you smoke, quit. Not only will you dramatically lower your own risk of lung and oral cancer, you'll protect your loved ones — including your pets, who are susceptible to health problems caused by second-hand smoke.

cancer 50 infographic

(Photo: American Institute for Cancer Research/AICR)