Sports Drinks, Not Just Sodas, Drive Up Weight in Teens

September 25, 2012 (San Antonio, Texas) — A study presented here at Obesity 2012: The Obesity Society 30th Annual Scientific Meeting widened the sugary-beverage/obesity link to include sports drinks. Currently, sales of sports drinks are rising as sales of sodas are tapering off.

Data on nearly 11,000 offspring of participants in the Nurses' Health Study II, aged 9 to 15 years, were tracked over time by Alison Field, MD, associate professor of pediatrics at Harvard Medical School in Boston, Massachusetts, and colleagues.

At the end of each 2-year interval of the study, the teens had gained almost 2.0 pounds for each can of soda they drank every day. If they drank 2 sodas a day, they gained 4.0 pounds over each 2-year interval.

Importantly, this study revealed the previously unknown consequence of drinking sports drinks; the teens gained an average of 3.5 pounds for every sports drink consumed per day.

"Sports drinks have an even stronger relationship than sugared sodas with weight gain," Dr. Field told Medscape Medical News. "I was surprised by that. I would have expected the weight gain to be comparable."

Over the life of the study, which began in 2004, consumption of sodas went down slightly among the participants, which mirrors the national trend, but consumption of sports drinks, particularly among boys, increased significantly, also mirroring the national trend.

"Sports drinks go under the radar," Dr. Field explained. "The danger is that they're sold as being part of a healthy lifestyle, of being active. Unfortunately, kids don't get 2 hours of exercise a day; if that were true, there wouldn't be a problem. Sports drinks also come in very large portions, and there's no line on the bottle that says, 'stop here.' They're simply not aware of how many calories are in a bottle."

Sports drinks are labeled as having 50 calories per serving, but each bottle contains multiple servings, so the calories add up: 130 calories per 20-ounce bottle and 200 calories per 32-ounce bottle. By contrast, sodas are most commonly sold in 12-ounce individual cans or bottles containing 120 calories.

Kids often drink the entire sports drink container at one time, so they consume all the servings in that single container, Dr. Field said. "The label says, 'amount per serving, 50 calories,' but it's not clearly labeled that a quart bottle contains 4 servings."

"We need to educate parents and clinicians about what constitutes a sugary drink," Dr. Field concluded. "Parents don't think of these as sugary drinks, but they should. Sports drinks are promoted by professional athletes as a healthy drink, but they really don't need to be used by kids unless they are continually exercising for long periods or they're in hot climates. I'm a marathon runner, and I don't consume 32 ounces of a sports drink even when I'm running 26 miles."

Daniel Taber, PhD, from the Institute for Health Research and Policy at the University of Illinois in Chicago, said he sees that schools are substituting sports drinks for sodas, with good intentions, but that it's not making any difference in lowering childhood obesity rates. "This study's results are truly remarkable," Dr. Taber said. "Especially the data revealing a bigger effect on a person's obesity from sports drinks than sodas."

Mislabeling is a pervasive problem and is a legitimate public-policy concern, according to Dr. Field. "One solution would be if beverage companies were required to label the calories per container." It wouldn't matter if it's 12, 20, or 32 ounces, she said, "the container would say how many calories are in it."

The study had limitations; the information was self-reported and the study group contained few ethnic minorities and youths from the low socioeconomic strata.

Dr. Field and Dr. Taber have disclosed no relevant financial relationships.

Obesity 2012: The Obesity Society 30th Annual Scientific Meeting. Abstract 27-OR. Presented September 21, 2012.