A new study finds that 1 in 5 people under age 40 now have metabolic syndrome, a group of risk factors that together increase the odds for many serious conditions, including diabetes, heart disease and stroke.

The rate of metabolic syndrome is rising in all age groups—as many as half of adults over 60 have it. But among 20- to 39-year-olds, the rate rose 5 percentage points over five years, the study reported.

Metabolic syndrome is a group of heart disease risk factors that occur together. They include:

• A large waistline,
• High blood pressure,
• Higher-than-normal blood sugar levels,
• High triglyceride levels (triglycerides are a type of blood fat),
• Low levels of good (HDL) cholesterol.

"The trends for metabolic syndrome are very alarming. A huge proportion of the adult population is affected—overall, 37% of adults in the United States. In young adults, the prevalence was remarkably higher than in our previous study through 2012," said study co-author Dr. Robert Wong, from the Veterans Affairs Palo Alto Health Care System in California.

Wong said the specific effects of metabolic syndrome in younger people haven't been well studied yet, but it's concerning to see because the impact is cumulative. "Young adults have so many years for damage and impact from metabolic syndrome," he said.

While many effects of metabolic syndrome take years to develop, a more immediate concern is COVID-19. People with metabolic syndrome, including younger people, have greater odds for developing severe complications if infected with the new coronavirus, according to Wong.

The study included data from a nationally representative group of more than 17,000 volunteers. More than 1 in 3 (35%) had metabolic syndrome. Rates were similar in both men and women.

The researchers compared data on cases in 2011-2012 to levels in 2015-2016.

Among 20- to 39-year-olds, metabolic syndrome rose during from 16% to 21%. For 40- to 59-year-olds, the rate went from 38% to 42%, and in those over 60, it rose from 47% to 50%. Only the change in the youngest group was considered statistically significant, Wong said.

Researchers also examined rates by race and ethnic group. They noticed that levels stayed roughly the same over the period among Blacks, but rose about 5 percentage points for whites. The biggest increases were seen in Asians, Hispanics and people who identified with other groups, according to Wong.

Among people 60 and older who did not identify as Hispanic, White, Black or Asian, the rate of metabolic syndrome was 64%. In Hispanics 60 and older, it was 57%.

While genetics may play a role, Wong said lifestyle appears to be the biggest contributor to the rise. He said targeted interventions to help people eat healthier and get more activity are needed.

"The challenge with metabolic syndrome is that for the most part, it has no symptoms. You may feel fine now, but these risk factors can culminate into serious outcomes like heart attack, stroke and cancers," Wong said.

Dr. John Osborne, director of cardiology at State of the Heart Cardiology in Southlake, Texas, reviewed the findings and said the rising rates in younger people were concerning.

"It's not just having a condition, it's the duration," he said. "The longer you have metabolic syndrome, the more likely it is that it will ultimately turn into diabetes, heart disease, stroke, acid reflux, sleep apnea and other problems."

Osborne said the biggest factors in the rise boil down to two big factors: "As a population, we're getting grayer [older] and we're getting fluffier [more overweight]."

While acknowledging that it can be hard, he said it's crucial for your health to try to eat better and move more. Osborne recommended a more Mediterranean diet—lots of plant-based foods and less processed foods.

"Try to eat real food and avoid simple sugars," he advised.