Study: Millennials’ Increased Risk for Some Obesity-Linked Cancers — 5 Takeaways

You may have heard news headlines recently about millennials getting cancer faster than baby boomers. This big news was based on a study by researchers at the American Cancer Society (ACS).

They found that 6 cancers proven to be related to obesity are increasing more rapidly in people younger than 50 than those older than 50.

What’s more, the risk for these cancers progressively increased for younger and younger generations — meaning that millennials, as the youngest group studied, had the highest risk.

Hearing such headlines can be alarming and hard to interpret. To make sure you understand what the study results mean to you and your loved ones, we talked to the study’s lead author, Hyuna Sung, PhD.

Here’s what she told us about the study’s key findings and the most important takeaway messages.

How Research Builds on Research

In 2017, ACS researchers Rebecca L. Siegel, MPH, and Ahmedin Jemal, DVM, PhD,  published 2 studies that found more young and middle-aged adults were being diagnosed with and dying from colorectal cancer (CRC).

These studies helped influence the ACS to update their guidelines for colorectal cancer screening to start at age 45 instead of 50.

This new research also found that the increase in CRC diagnoses was not likely due to improvements in screening and were more likely due to some other causes.

The duo, plus Hyuna Sung, PhD, thought obesity might be one of those “other causes,” so they explored their hypothesis with this study. 

What the Study Found

Sung, 2 of her colleagues in the ACS Surveillance and Health Services Research Program, and a researcher from the National Cancer Institute worked together on the study. They reviewed records for the years 1995 to 2014 for patients with any of 30 cancer types. The group represented 67% of the US population. Of the 30 cancers, 12 are known to be linked with obesity. The other 18 types are mostly related to smoking or infection, or both. They published their findings in The Lancet Public Health. They found:

  • Year-after-year, the rate of increases for developing 6 obesity-linked cancers was faster in younger adults than in those older than age 50. The 6 cancers were of the kidney (See graphics.), pancreas, gallbladder, endometrium (lining of the uterus), and colon or rectum, as well as multiple myeloma.
  • The youngest groups (ages 25 to 34) had the fastest increase for those 6 obesity-related cancers. The team found a similar pattern for 2 other cancers that are not related to obesity.
  • Recent generations showed increased risks for the same 6 obesity-linked cancers. In fact, the youngest generation of adults studied—those born around 1985—have the highest risk for those cancers. Sung explains, “a son born in 1985, for instance, has a higher risk for developing these obesity-related cancers throughout his life than his father (born in 1950) did.”

6 Obesity-Related Cancers on the Rise

Compared to people born around 1950, those born around 1985 had a:

  • 2 to 5 times increased risk for kidney, gallbladder, pancreatic, and endometrial cancers
  • Nearly twice the risk for colorectal cancer
  • Just over 1.5 times the risk for multiple myeloma 

Takeaway #1: We don’t know if obesity is the cause of the trend

Obesity may have been one of the strong contributing factors, says Sung, but it’s not the only driving factor. “We don’t know exactly what those risk factors are. Unhealthy habits such as the way you eat and get exercise, which are linked with obesity, may be factors, or they could include some things that are not even related to obesity.”

We saw the trends in age with cancers known to be related to obesity, Sung says, but we didn’t know the BMI of the people studied. To learn more, we need studies that include information about obesity as a risk factor and health behaviors that may increase the risk for cancer. That way, we can formally assess the impact of these risk factors on the change in cancer rates, especially the emerging trends in adults younger than age 50.  

Takeaway #2: Something is going on with the younger age groups.

The dramatic increases in cancer rates among adults younger than 50 imply “that certain risk factors are newly introduced to young people, or some risk factors have increased very fast among them,” Sung says. To better understand this trend, we need studies that focus on the effect of excess body weight and other risk factors that start early in life, as in children, teens, or adults younger than 50, she says.

Takeaway #3: We know obesity is linked with many cancers, but we need to learn more.

The risk for certain cancers may increase the longer a person is obese, Sung says. “Obese kids tend to carry their body weight into their adulthood. That means young people growing up now have a longer cumulative lifetime exposure to body fat compared to those in older generations. Increasing evidence supports that excess bodyweight during young adulthood may increase risks for certain cancers later in life.” We need to evaluate studies that include how to properly measure body fat, the effects of weight gain at different ages, and the effects of how fast someone gains weight.

Takeaway #4: Older adults still get more cancers than younger adults, for now. . . 

Although more adults younger than 50 are getting certain obesity-related cancers, that doesn’t mean that those cancers didn’t increase among older adults,” says Sung. Our study showed that obesity-related cancers generally increased across all age groups. “It was just that the pace of increase was much faster among those under 50 compared to those older than 50.” In contrast to obesity-related cancers increasing in recent generations, Sung says, smoking- and infection-related cancers have decreased in them due to prevention efforts. 

“However, there’s a large increase in the number of young people who are overweight and obese, says study coauthor Ahmedin Jemal, DVM, PhD, “The increasing risk of obesity-related cancers in younger generations, has the potential to halt or reverse the progress we’ve achieved in reducing the death rate from cancer in the last 20 to 30 years.”

Takeaway #5: The study has significant public health implications especially for policy makers and health care providers.

To help prevent obesity and help those who have it already, society-level changes are necessary, Sung says. “Less healthy foods are promoted more and are more available than healthy foods. At the same time, city layouts and other issues make it easy for people to be less active,” she says. “That’s why we need policy-led interventions that will control and prevent obesity at the population level.”

The study authors suggest communities use methods that have been proven to reduce obesity rates. These methods include urban planning that promotes physical activity, restrictions on advertising for calorie-dense food, and taxes on sugar-sweetened beverages. 

The bottom line, Sung says is to “try to achieve a healthy weight and maintain it throughout your life to lower your risk of cancer.” Helping your children maintain a healthy weight can help reduce their obesity-related risks for cancer when they are adults.