Sports drinks aren’t necessary for children and teenagers and are likely to contribute to obesity, according to U.S. researchers urging parents to limit consumption of the beverages.

While adolescent athletes engaged in vigorous physical activity may benefit from the carbohydrates and electrolytes provided by drinks such as Gatorade and Powerade, researchers said water should be the beverage of choice for hydration.

“For most children engaging in routine physical activity, plain water is best,” Holly J. Benjamin, a co-author of the study published today in Pediatrics, the journal of the American Academy of Pediatrics, said in a statement. “Sports drinks contain extra calories that children don’t need.”

Obesity in children and adolescents ages 2 to 19 rose in the United States to almost 17 percent in 2007-2008 from 5 percent in 1971-1974, according to the Centers for Disease Control and Prevention in Atlanta. The number of all Americans who are obese has remained constant since then, according to a January study by the CDC. Obesity, which is a measure of body mass index, contributes to higher risk of diabetes, heart attacks and strokes.

Today’s study also focused on the effects of energy drinks that contain caffeine and other stimulants.

These beverages can damage children and adolescents’ neurologic and cardiovascular systems and shouldn’t be consumed, said Benjamin, a University of Chicago associate professor of pediatrics and a physician specializing in sports medicine, and Marcie Beth Schneider, a study co-author and a pediatrician in Greenwich, Conn., specializing in adolescent medicine.

Some energy drinks have more than 500 milligrams of caffeine, or the equivalent of 14 cans of soda, Schneider said in a statement.

Rockstar, made by Las Vegas-based Rockstar Inc., has 80 mg of caffeine per 8-ounce serving, more than twice the amount in the same-sized serving of Coca-Cola.

About 28 percent of children ages 12 to 14 regularly consume energy drinks, according to a study published in the March issue of Pediatrics.

The authors recommended physicians educate children and parents on differences between sports and energy drinks and the potential health risks.