To the horror of some of you anti-cardio guys, I am a marathon runner in addition to avid weight lifter. I'm able to keep my mass with careful nutrition and planning my weight routines separate from running.

In any case, my question relates to my weight after longer runs. This past weekend, I did a 23 mile training run and expected to be underweight on Monday because I just couldn't replenish all 4000 calories needed (RMR + 2300 calories burned during run).

To my surprise, I was 3lbs heavier and it dawned on me that I may be retaining water because I was taking salt tabs/electrolyte tabs during the run to maintain adequate hydration.

My question is...what truth is there to this theory of mine? How long does your body hold on to this extra water weight?

It's not concerning, I just found it perplexing considering I have had trouble reaching maintenance calories.

For me 2-4 days depending on how much water I take in and how much salt.

I noticed 3 days later and I am back at normal weight.

I can retain 5 or 6 pounds of water after a big, salty meal...

Usually shed the water by the time I get up on the 3rd morning....