Wed, July 31, 2024 at 6:38 PM EDT·5 min read

Experts are sounding the alarm as rates of 17 types of cancer in millennials and Gen X-ers have risen dramatically in recent years, a new study shows. For certain cancers, people born in 1990 face two-to-three times the risks that those born in 1955 did, according to the research published in the journal Lancet Public Health. The findings echo the recent worrying rise in young people developing colorectal cancer, but add more forms of the disease to the list of concerns.

It's too soon to say what is driving the increase in what experts call "early onset" cancers, but they warn that it's not just due to better screening; people are dying of these diseases at rates and ages not seen in their parents' generations.

Here's what to know about the generational risk of cancer and what you can do to reduce yours.

What did the new study find?

On average, the rates of 17 types of cancer, including pancreatic, breast and gastric cancer, have risen with each new generation since 1920, the study found. Previous ACS research had shown that rates of 11 cancers, including pancreatic, colorectal, kidney, uterine and testicular cancer, had been increasing among young adults. The new study added eight more types of cancer to that list:

• Gastric cardia cancer (a cancer of the stomach lining)

• Cancer of the small intestine

• Estrogen receptor-positive breast cancer

• Ovarian cancer

• Liver and bile duct cancer

• Non-HPV-associated oral and pharynx cancer (only in women)

• Anal cancer (only in men)

• Kaposi sarcoma (a cancer of the blood vessel lining and lymph nodes, only in men)

Rates doubled or even tripled for some of these cancers, including kidney, pancreatic and small intestine cancers, in people of either gender. For women, liver cancer incidence has increased two- to threefold since the 1920s. Even cancers that seemed to be in decline for baby boomers and other older generations - including some breast cancers and testicular cancer - are now a greater risk again to millennials and Gen X-ers, the study found.

More young people are dying of some of these cancers as well; mortality from colorectal, gallbladder, testicular and uterine cancers has increased over the generations, as has the fatality rate of liver cancer, but only for women. "That really stood out because the concurrent increase in mortality [and diagnoses] suggests that what we see is not just an artifact due to potentially more frequent screening and diagnosis," lead study author and senior principal scientist of surveillance and health equity science with ACS, Hyuna Sung, tells Yahoo Life. "Instead, it indicates a genuine increase in risk, with the increases in incidence sufficient to outpace improvements" in diagnostics and treatment.

Why is this happening?

While the new study doesn't answer why this is happening, Sung and other experts have a prime suspect in their sights: obesity. Ten out of 17 of the cancers that are becoming more common over the generations have been linked to obesity, the study authors noted.

Research to suss out exactly how obesity might contribute to or cause cancer is ongoing, but there are some leading theories, Timothy Rebbeck, professor of cancer prevention at the Dana-Farber Cancer Institute, tells Yahoo Life. "When someone is obese, a lot of things change in the body, including chronic inflammation that leads to years and years worth of damage to cells and tissues in the body, which can lead to cancer," he explains.

According to the MD Anderson Cancer Center, it may not be a person's body mass index (BMI) directly; rather changes to insulin sensitivity and an increase in certain hormones might fuel out-of-control cell growth and, in turn, lead to cancer.

Coinciding rises in obesity and cancer rates, especially among young adults, suggest that the problem may begin in childhood or perhaps even before people are born, says Rebbeck. "That process of damage to your cells is starting earlier and earlier, so if there's a 20-year lag from this obesity exposure and it starts at age 10, it's in your 30s or 40s when cancer risk arises," he hypothesizes. The timelines also suggest there may be other early life environmental exposures, including factors like antibiotic use or diet that may alter your gut bacteria, which may influence a person's cancer risk.

What you can do to reduce your risks

While the findings are alarming, experts say not to worry too much. Here's why: "Cancers diagnosed before age 50 are still relatively rare," Rebbeck says. Only about 350 out of every 100,000 cases of cancer diagnosed each year are found in people between ages 45 and 49, according to the National Cancer Institute. "It's not something that people need to start panicking about … but we want people to be informed and start doing things that might have an impact," says Rebbeck.

That just means making straightforward changes to live the healthiest lifestyle you can and reduce your cancer risks, experts say, by doing your best to maintain a healthy body weight, exercising regularly, eating a balanced diet low in ultra-processed foods and red meat and high in plants and fish like salmon, drinking minimally and not smoking. "None of these things are easy, but they are the things we can recommend," Rebbeck says.

It's also important to know your family history and see a health care provider if you notice any changes that could be early warning signs of cancer. For young people, there are "unique symptoms" of some cancers, such as colorectal cancers, including "fatigue, rectal bleeding, abdominal pain, altered bowel habits, or unexplained weight loss, which are really considered red flags for early onset cancer," says Sung.