If I lose weight, how much can I expect to improve on my running race times?

Question

I'm a 27 year old female. I'm 5'5" and weigh 132lbs. 18.5% body fat. I've been running for about a year now and my current 5k time is 23:30 and my half marathon time is 1:50:45. I would really like to improve my race times. Obviously, training is the best way to improve, but will losing 10-20lbs also help. I've noticed that most serious racers are very thin. And if so, how much will this help? I find it very hard to lose weight while I'm training....any tips?

Answer 1

There are so many variables that you will not find a concrete answer.

The number I have heard quoted most often is 2-5 seconds per mile, per pound lost.  EDIT: (Revised and I'm looking for my link)

Again, it's unscientific, and only you can decide what your ideal weight is based on BMI and activity.

Answer 2

Losing weight helps up to a point.  So if you were 160lbs you'd see an improvement by losing weight.  However, your weight already seems well within range.  If you are too thin you will run slower because you lack muscle mass.  In addition, too low of a body weight increases the risk of injury and getting sick.  Your % body fat is already low.  Losing 20lbs would be too much.

Everyone has their own body type and some runners are thinner than others.  Usually a runners weight naturally stabilizes at the ideal for that runner for their body type. I'd focus on training, eating a healthy and balanced diet and your times will improve.

Answer 3

Unlike David I think weight does matter when trying to get faster, sure you can be strong in a muscular sense.......but if your carrying a lot of fat it will slow you down for sure(especially in the belly area!!).   The longer the race is the more you will see this is true!!  If your 132 which you said(20 lbs. is too much for you to lose!), and your well put together it will be hard.....but if your 132 and could stand to lose some fat in certain areas (mainly belly and butt) you'd be surprised how losing 5 lbs. will make it easier/faster times.  I'm a experienced runner, mainly 5K and when I gain like 4-5 lbs. (seems to be in stomach area) it slows me down and makes it much more difficult to run.  I'm thin, but carry more muscle than most racers I compete against.  You know your body the best.......so evaluate what you think is your weakness and get faster girl..........  Good Luck

Answer 4

Try using the calculator below. It should show you how much body fat you have, how much you should lose, and the second link shows you the chart which shows you how much body fat you should lose,

Answer 5

In response to a similar question, Runner's World quoted the number 2 seconds per mile per pound.

The question was asked about marathon times, so it may not apply to shorter distances.