Weight loss when running a marathon linked to faster finish

A new study released online December 21 revealed that runners who lose three percent or more of their body weight during a marathon finish faster.

The study tracked 643 contestants who completed the 42-kilometer Mont Saint Michel Marathon in France in 2009. The runners were weighed immediately before and after the race, with the degree of weight loss ranging from an eight percent loss to a five percent gain. Neither age nor gender affected weight loss during the run, said researchers.

The fastest runners, finishing in less than three hours, lost three percent of their total body weight. Those losing 2.5 percent of their body weight took between three to four hours to cross the finish line; runners losing less than two percent took four hours or longer. The slowest in the group were those who gained weight by drinking the most liquids. Researchers advised all of the participants to drink either 250 milliliters of water or an energy drink every 20 minutes.

As more and more people lace on their running shoes to train for marathons this year, researchers are busy gathering empirical evidence on the long-distance race's affects on the body, or discovering new ways to enhance a runner's performance. Biomed engineer Benjamin Rapoport of Harvard Medical School and MIT in the US recently offered runners a tool to complete the race more successfully: a mathematical formula to help runners avoid hitting "the wall," when dramatic fatigue sets in, typically around 33 kilometers. To calculate the ideal running pace to avoid the wall, Rapoport uses a measure of aerobic capacity called VO2max, which measures how efficiently a body consumes oxygen. It's usually measured with specialized equipment, but can also be estimated by measuring heart rate while running at a steady pace.

The weight loss study is published in an upcoming print issue of the medical journal British Journal of Sports Medicine, and available online here.

Access Rapoport's calculator here: http://endurancecalculator.com

Training for a 2011 marathon? Get expert advice here:
http://www.runnersworld.com/subtopic/0,7123,s6-238-520-492-0,00.html
http://www.ucsfhealth.org/education/running_a_marathon_training_tips/