Effect of weight loss on running speed.

This topic comes up quite often. This link was posted on one thread, and it should be the most reliable as it relies on a mathematical equation rather than theories and speculation. Make sure to read the Important note at the bottom.

http://www.runningforfitness.org/calc/weighteffect.php

probably won't get that much faster.

Yeah, I did the calculator thingy, and I run aroung 18 mins for 5K (indoors), and I find it really hard to believe that if I lost just four pounds, I'd drop 35 seconds. I actually weighed about 5 pounds lighter a couple years ago, and I was still around 18 mins for indoor 5K. I do believe that excess weight can affect you, but it must be a lot of weight, and I don't think it affects you as much as people think it does--especially a few pounds.