 -- Cancer. To many of us, it may seem scary, mysterious, or even inevitable. Now, a new study suggests that nearly half of the country’s cancers may be preventable through decisions we make every day.

Researchers with the American Cancer Society looked at data on cancer incidence and deaths, finding that 42 percent of cancer cases in the United States -– and nearly half of cancer deaths – are linked to preventable risk factors like cigarette smoking, exposure to secondhand smoke, excess body weight, alcohol intake and dietary choices.

Cigarette smoking, in particular, was connected to far more cancer cases and deaths than any other single risk factor, accounting for 19 percent of cancer cases and 28.8 percent of deaths. Overweight and obesity came in second, responsible for 7.8 percent of cases and 6.5 percent of deaths, while alcohol intake was the third most important factor, leading to 5.6 percent of cancer cases and 4 percent of deaths.

“The results indicated that we can prevent a substantial proportion of cancers with the help of behavior and prevention strategies,” said lead study author Dr. Farhad Islami, Strategic Director of Cancer Surveillance Research at the American Cancer Society. Islami noted that he and his team believe that the percentages they reported are actually an underestimate of the cancers that could be prevented with simple lifestyle tweaks.

The good news is that the rate of death from cancer in U.S. has decreased by 25% over the past several decades. But experts estimate that in 2017, 1.6 million new cases of cancer will be diagnosed, and 600,000 people will die of their cancer –- which is why experts in the field agree that more needs to be known about how to prevent these cancers before they strike.

“[The study] is an incredibly important piece of research because it is relevant to understanding cancer risk factors,” said Elizabeth A. Platz, deputy chair of epidemiology at the Johns Hopkins Bloomberg School of Public Health, who was not involved in the study. “I am very excited about the paper. It furthers the point that primary prevention is the future. It would be better for everyone to prevent cancer upfront.”

Platz added that the emphasis on obesity is particularly timely.

“The obesity epidemic started in the 1980s; it then plateaued but now seems to be on the rise again,” she said. “The worst part is that this is evident in children too.”

Out of the preventable cancers studied, lung cancer had the highest number of associated cases and deaths, followed by colorectal cancer. Interestingly, cancer cases and deaths linked to smoking, red and processed meat consumption, hepatitis C infection, UV radiation and HIV infection tended to be higher in men compared to women. On the other hand, cancer cases and deaths linked to excess body weight, alcohol intake, physical inactivity and human papilloma virus (HPV) infection were higher in women. Excess body weight causes twice as many cancers in women as in men.