Thursday is World Cancer Day, which is aimed at uniting the world’s population with the goal of defeating cancer.

There are about 8.2 million cancer death around the world each year, with about 14 million cases annually, and this number is expected to rise by 70 percent over the next 20 years, the World Health Organization says.

In the U.S., heart disease is still the leading cause of death but cancer is catching up fast.  Although the death rates are falling for both, heart disease is dropping more steeply.  This means cancer will become the leading cause of death in the country in 2030, according to the American Society of Clinical Oncology.

Although it isn’t definitely known what causes cancer, experts agree that the following lifestyle changes could cut your risk of developing it by up to 40 percent:

Stop smoking. Cancer experts agree that quitting smoking is the biggest way to reduce cancer risk. Although smoking is most strongly linked to lung cancer, causing an estimated 87 percent of cases, the habit also contributes to cancers of the mouth, larynx, esophagus, throat, bladder, kidney, liver, stomach, colon, rectum, and cervix, as well as acute myeloid leukemia, the National Cancer Institute says.

Lose weight. It’s estimated that obesity contributes to one-third of all new cancers, so staying lean should be on the top of everyone’s cancer-prevention list, according to a joint report issued by the American Institute for Cancer Research (AICR) and the World Cancer Research Fund (WCRF).  Staying at an ideal weight helps protect against breast cancer, colon cancer, and cancer of the uterus, kidney and esophagus, the AICR/WCRF report says.

Engage in physical activity. Over the years, Americans have become increasingly sedentary. This leads to obesity, but being sedentary is also considered an independent risk factor for cancer. According to the American Cancer Society, being physically active can cut cancer risk by 30 percent to 40 percent, with those who are the most active reaping the most benefit. This is particularly true for cancers of the colon, breast, lung, and pancreas, as well as some  aggressive forms of prostate cancer.

Limit or cut out alcohol. Consumption of alcohol has been slowly rising in the U.S., and an estimated 67 percent of Americans now imbibe. Alcohol is composed largely of ethanol, which is a carcinogen that is linked with several cancers. This includes cancers of the mouth, pharynx, larynx, esophagus, colon, breast and liver, the AICR/WCRF report says.

Reduce processed food in your diet. There’s increasing evidence that eating processed foods – especially meats that contain nitrates – contributes to an increased risk of colon and stomach cancer. Studies also show that the more of these foods are eaten, the higher the risk of cancer.  Instead, choose fresh foods, and bulk up on fruits and vegetables, as well as foods high in fiber to reduce your cancer risk, the American Cancer Society says.