how will 5lbs affect my 5k?

16:58? What grade are you in? Also, what did a week of training look like for you? Just depends if your training was high QUALity not QUANTity.

you will run slower if you have less pounds because you need energy to be able to run long distances. the ideal weight for a long distance runner is anywhere from 190-240lbs depending on your height

The only way a distance runner should be 190+ is if he is 6'3+

Less weight is better to an extent.

I have been running for 3 years but I am 21 years old

honest wrote:

you will run slower if you have less pounds because you need energy to be able to run long distances. the ideal weight for a long distance runner is anywhere from 190-240lbs depending on your height

If you have extreme height say 6'6' then you are going to need to weigh about 285 lbs to peak.

The normal formula is 2 seconds per mile per pound.

You have a really fast PB, I'm jealous. They say you save 3 seconds per km per kilo (or for Americans, I don't even know what that is for pounds/mile) but obviously training is more important. I am 2kg heavier than my last 5k PB time but I just beat it by a couple of seconds. If some of your gain is leg muscle then you may well run faster. To be honest I think 5lbs is so small it won't make much of a difference. It's less of a factor than training, and physical and mental race preparedness.