TUESDAY, Nov. 30 (HealthDay News) -- Runners who took part in a two-month, 4,500-kilometer race lost 5.4 percent of body volume during the event, including 50 percent of their body fat, according to a new report.

The runners also lost an average of 7 percent of muscle volume in their legs because of the huge amount of energy consumption, the researchers said.

In the study, the investigators analyzed data collected from 44 participants in the TransEurope-FootRace 2009, which began in southern Italy and ended in northern Norway. The findings were presented Nov. 29 at the annual meeting of the Radiological Society of North America, in Chicago.

"Due to the exceptional setting of this study, we could acquire huge amounts of unique data regarding how endurance running affects the body's muscle and body fat," Dr. Uwe Schutz, an orthopedics and trauma surgery specialist at University Hospital of Ulm, Germany, said in a news release from the society.

"Much of what we have learned so far can also be applied to the average runner," Schutz added.

For example, the researchers found that it can be safe to "run through" some leg injuries, such as intermuscular inflammation in the upper or lower legs. They also found that fat is the first tissue affected by running, and the greatest amount of overall fat loss occurs much earlier in a running program than previously believed.

"When you just begin running, the effects of fat reduction are more pronounced than in athletes who have been running their whole life," Schutz explained. "But you should do this sport constantly over the years. If you stop running for a long time, you need to reduce your caloric input or opt for other aerobic exercises to avoid experiencing weight gain."

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