Heavy tackles and 300-pound nose guards are common in pro and college football. Now a study shows the trend toward beefier, overweight linemen is emerging at the high school level.

Researchers at Iowa State University found nearly half of the offensive and defensive linemen playing on Iowa high school teams qualify as overweight, and one in 10 meet medical standards for severe obesity.

"These are 15- and 16-year-old boys that have a weight and body-mass ... that as they enter adulthood puts many at a very adverse health condition," said Dr. Joe Eisenmann, co-author of the study and a professor in pediatric exercise physiology at Iowa State.

The study appears in Wednesday's Journal of the American Medical Association.

For years at the pro and college level, teams have sought bigger, stronger linemen who are harder to budge. Players have responded by adding weight and muscle mass, making the 300-pound lineman fairly common, sports medical experts said.

Recently, however, the National Football League and players have taken greater note of health risks for heavy athletes because of two high-profile NFL player deaths and a 2005 study, which concluded that 56 percent of NFL players fit medical standards for obesity.

The size, bulk and ever-widening girth of the pros apparently has not gone unnoticed by those dreaming of one day playing at the next level.

"Sure I look at college players and pro players a lot and size them up," said Chad Wilson, a junior who started at center last season for Iowa City West High School. He wants to add at least another 20 pounds before next season.

Pressure to get bigger, stronger, heavier may come from parents and coaches, but there is also a desire from within, players said.

"You want to have the weight to be able to compete in the conference we're in," said Thomas Reynolds, a junior linebacker hoping to switch to the defensive line next season.

The study's researchers began by gathering height and weight data of 3,686 varsity linemen available from rosters from all classes of Iowa high school football teams. They used that data to calculate a body-mass index, the same tool used for the NFL study.

Of the players analyzed, 28 percent were deemed at risk of being overweight and 45 percent fit the standards for being overweight, including 9 percent who met adult severe obesity standards.

Researchers believe the study is one of the first _ and most comprehensive _ appraisals of obesity in high school football.

"We don't suspect, though, that Iowa is unique in any way," said Kelly Laurson, a graduate assistant and co-author of the study. "I suspect that states with an even richer high school football tradition, like Florida and Texas, may have an even bigger problem."

But the researchers and sports medicine experts acknowledge the study is not perfect.

The roster data was obtained in the preseason before athletes had a chance to get in shape, and the BMI formula can, in some cases, be deceptive, they said.

Dr. Edward Wojtys, an orthopedic surgeon and chief at the University of Michigan Sports Medicine Service, said the BMI fails to account for muscle mass and lean tissue and is less accurate than more sophisticated measuring techniques.

"On the other hand, there is still an obvious and growing problem of obesity among football linemen," Wojtys said. "The rules have changed in ways that favor larger and larger-sized bodies rather than smaller, athletic ones. It's not a good trend and one we should be concerned about."

Health experts also said the results are no surprise in a society dealing with high rates of child and adolescent obesity. Overweight children and teens face higher risks for heart disease, high blood pressure, diabetes and weight problems through adulthood.

They said it's impossible to lay blame on any single source or factor.

"But I think if we're honest about it, at least in this case, we'd have to look at the role models for these young athletes," said Dr. George Phillips, a pediatrician at the University of Iowa's Sports Medicine Center.

"Most of these kids aren't going to play professionally or even at the college level. So what we need to do is to make sure if they're going to add weight, muscle mass, that they do it in a healthy way."