Football season usually means cooler weather and exciting times for high school and college age kids.

This year though, the extreme heat is not only causing great concern among parents, students and coaches- it’s been responsible for at least 3 deaths. So far this year, there have been four football-related deaths; two teenage football players from Georgia, a high school player in South Carolina, and a 55-year-old football coach in Texas.

According to a recent study excess weight, along with the high temperatures, could be a contributing factor for certain athletes.

An analysis of 58 heat-related deaths among U.S. football players from 1980 to 2009 showed that about 80% involved players who were obese by the conventional definition of a body mass index of over 30.  Ninety-five percent were overweight or obese.

The rate of heat-related illness and death among football players has increased since the mid-1990s, according to Andrew J. Grundstein, PhD, of the University of Georgia in Athens, first author of the study.

The reason for the increase is not entirely clear but could reflect the increasing body weight of players, he said.

Most of the deaths occurred in August, when fall practice typically begins, and most occurred within the first two weeks of practice. Surprisingly, a majority of the deaths occurred during morning practices.

"Mornings may be cooler, and a lot of coaches may recommend having practices in the morning because it is cooler, but high humidity levels can make the conditions very oppressive and stressful," Grundstein said during a teleconference, sponsored by the Union of Concerned Scientists.

"I think people may put their guard down because they think the risk of heat-related illness is less in the morning," he added.

Grundstein also noted that more than 60% of the deaths happened on days when practice should have been cancelled.