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Weight Loss During Marathon Improves Running Time

Study Suggests Less Fluid Intake May Improve Performance for Marathoners
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Take-Home for Runners

Noakes has a simple take-home for distance runners: "Drink to thirst," he says. "That is all you need to know."

But he points out that's very individual. "For some that will be 800 milliliters per hour (28 ounces); for others it will be 100 milliliters per hour (4 ounces)."

Noakes blames the sports drink industry in the U.S. for persuading runners to overdrink during a race. "The sports drink industry in the U.S. unfortunately promotes the false idea that drinking to thirst is not adequate. That is why athletes in the U.S. are more likely to overdrink than athletes in any other country."

Second Opinion

William Roberts, MD, medical director for the Twin Cities Marathon in Minneapolis-St. Paul, Minn., reviewed the study for WebMD but was not involved in the research.

''Fast runners are fast despite their body weight and fluid status," he says. "Would they individually be faster at minus 2% [body weight] compared to 0% or minus 6% is hard to judge from this study and others, but as a group the faster runners are carrying less weight at the end of the race."

But he does agree with Noakes on the important point: "Drink to thirst probably works for most and 750 milliliters per hour [25 ounces] may be too much fluid for runners who do not sweat very much."

"Slow runners probably sweat less and have more time to drink, so they really need to pay attention to the risk of drinking too much."

He points out that ''there is no mention of medical outcomes so no conclusions about the safety of losing body weight can be made."

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