(Reuters Health) - Severe obesity rates have been on the rise nationwide since the turn of the century, disproportionately affecting children and adults in rural communities, two U.S. studies suggest.

Researchers examined data on height and weight collected from 2001 to 2016 for adults 20 and older and for youth ages 2 to 19. Severe obesity rates were higher in rural areas for youth as well as for men and women, while overall rates of obesity were higher only for rural women, researchers report in JAMA.

In rural communities, severe obesity rates more than tripled for men and more than doubled for women during the study period, while climbing 29 percent among young people. Obesity rates in rural areas, meanwhile, rose about 9 percent among children and teens and about 36 percent for adults.

“A major finding that surprised us was this difference between obesity and severe obesity,” said Cynthia Ogden of the U.S. Centers for Disease Control and Prevention in Hyattsville, Maryland.

“Severe obesity affects quality of life and has serious health risks,” including an increased risk of premature death and several cancers, Ogden, lead author of the youth study and senior author of the adult study, said by email.

About 10 percent of rural men had severe obesity in rural communities by the end of the study period, compared with 4 percent of urban men, the adult study found. Almost 14 percent of rural women had severe obesity, compared with 8 percent of urban women.

Differences in education levels, smoking status, age, and racial demographics in rural versus urban communities didn’t appear to explain the different rates of obesity and severe obesity among adults.

More than 9 percent of rural youth had severe obesity by the end of the study period, compared with about 5 percent of urban children and teens.

Obesity and severe obesity were more common among black and Hispanic youth than white children and teens, and also more likely to develop in older youth and children from households headed by an adult with limited education.

Children and teens are considered obese when their weight is higher than 95 percent of other youth their same age and sex. They’re considered severely obese when their weight is 20 percent higher than the cutoff for obesity.

For adults a body mass index (BMI) of at least 30 is considered obese, and a BMI of at least 40 is classified as severely obese. (An online BMI calculator for adults is available from the U.S. Centers for Disease Control and Prevention, here: bit.ly/2ylWKJC.)

One drawback of using BMI is that it doesn’t distinguish between muscle and fat. Therefore, obesity rates might not have been as high as they appeared, particularly among the adults.

The studies also weren’t controlled experiments designed to prove whether or how certain aspects of rural life might obesity more likely to develop.

“When looking at the global epidemic of obesity, we ironically often blame urbanization as a factor due to urban centers having more fast food locations, a pace of life where there is less emphasis on family meals, and work environments that are not physically taxing,” said Dr. Rekha Kumar of Weill Cornell Medicine’s Comprehensive Weight Control Center and NewYork-Presbyterian in New York City.

“We have passed that stage in the U.S. and measures are being taken in some but not all urban areas to prevent obesity,” Kumar, who wasn’t involved in the studies, said by email. “All (of) these factors such as energy sparing technology, fast food, and desk jobs have now reached rural areas as well in the U.S. so we are seeing an escalation of the obesity epidemic.”

No matter where people live, the key to preventing and reducing obesity comes down to healthy eating and regular exercise, said Ashlesha Datar, a researcher at the University of Southern California in Los Angeles who wasn’t involved in the studies.

“The only difference is that folks in rural areas are at a higher risk and we need to figure out whether that is due to lack of opportunities for pursuing healthy behaviors or other constraints,” Datar said by email. “What might work for people in the cities might not necessarily work for those in rural areas.”

SOURCE: bit.ly/2th8uY4 and bit.ly/2ypKY0R JAMA, online June 19, 2018.