Bigger Leg Muscles and Weight Gain

Question
QUESTION: My question is 2-fold....could you please answer an on-going debate I'm having with runner friends?  I have been a runner for 20+ years but have doubled my mileage/wk in the last year (currently around 80 mpw).  I can't stuff myself into my jeans anymore...jeans that almost fell off me last year.  My thighs are HUGE!  Friends say it's just water retention in my legs b/c I run so much and if I would take 3-4 days off, my legs would shrink back to their "normal" size.  I say I don't think so.  But why are my legs so much bigger now if I'm supposed to be breaking down muscle mass by running?  Also, I've GAINED weight.  I am currently training for marathons 4 and 5 and never thought I'd gain weight running more miles.  I've gained about 10-15 lbs since last year (when I picked up the mileage).  For the most part, I eat grilled or baked chicken (rarely eat red meat), veggies and whole grains.  I hate fruit.  I do splurge on occasion (pizza, dessert, chips) but this is a treat I allow myself only 1-2x/month.  

So what is going on with my leg muscles?
What is going on with gaining weight and running more (frustrating)?

Thanks for any help!


ANSWER: Laura,

This is a strange phenomenon but I'll try my best here.  First off, 80 miles per week is huge mileage...especially from doubling from last year.  I would at least back off to 40-50 miles every 4th week to give your body a break and to prevent injury.  I don't doubt that you might be fresher and faster after these periodic layoffs.

Now to your question...I'm having alot of trouble envisioning how you could gain 15 pounds when you're running 80 mpw and increasing from 40.  Also, running does little to increase leg size unless you're a man doing intense hill or speed work.  But as a female marathoner, this is strange indeed.

You're running 80 mpw but you splurge on pizza, chips only once a month.  I would want to know how much you weight and how many calories a day do you eat.  Also, what were your eating habits a year ago?

The more I think about it, the harder it is to figure out.  I can say this for certainty.

Running 80 mpw will make you very lean and it is highly unlikely that you will gain weight unless your caloric intake greatly increases to account for this increase.  I don't doubt that your thigh size is directly related to your weight gain.

Is your weight gain from fat or are you still the same leannness and assume you've gained muscle?

Finally, any chance that you're pregnant???

Please give me just a bit more info as what you're telling me is quite uncommon.

Thanks, Larry

---------- FOLLOW-UP ----------

QUESTION: Hi Larry,

Yes, I actually do drop my mileage back to around 60-70mpw every 3-4 weeks and then pick it back up to at least 80mpw.  I hit a high of 100mpw back in early Aug.  I am currently almost at the end of my taper for my next race (this weekend) so it's dropped off significantly for that.  Strangely, I have lost 5 lbs since I lowered my mileage.

I don't keep a very good diet log so to the best that I can reconstruct notes....I eat about 2000-2500 calories a day.  I am 5'8" and currently weigh around 160 lbs., with an "athletic" build.     

Last year, I ran so I could eat.  This year, I eat so I can run.  With that said, my splurges of pizza, dessert, etc. happened most often after one of my long runs of 20-22 miles, but not every long run.  I should be able to run 80mpw and pretty much burn off anything I occasionally splurge on, right?     

It's hard to say whether I've gained just muscle vs fat.  In the summer months, I had stopped doing weight training (arms only) and ab work.  No reason, except for laziness.  I can pinch an inch on my waist and arms but definitely NOT on my legs or backside!!  So it's hard for me to tell if the overall weight gain is from fat or muscle since I've gotten "soft" in a few places.  Does that make sense?  But my legs are definitely more "solid" than ever before.  No, I'm not a man doing intense hillwork or even a woman doing intense hillwork or speedwork :-)  

Looking at my notes.....yikes, is it possible that I am not eating enough calories for 80 mpw and my body was in a starvation mode and holding weight?  Maybe I wasn't fueling enough on my doubles days?  Seems strange that since dropping my mileage, I have lost 5 lbs.  

Definitely NOT pregnant!  Been there, done that.

Thanks for helping get to the bottom of this!

Answer
Hi Laura,

I would recommend buying a body fat scale.  Body weight is notoriously unreliable to assess leanness.  This way, if you lose or gain 5 pounds, you will have a clear understanding of the composition of that weight.  Gaining 5 pounds from lean mass isn't such a bad thing.  Conversely, losing 5 pounds...but all of it from water and muscle is not good.  

Regarding body weight, I would just look at overall long-term averages in your weight since everyone, esp. distance runners, will have great short-term fluctuations depending on hydration, recent food intake, etc.  A 5-pound loss today could be gained right back depending on many factors.

I don't doubt that your body water levels fluctuate quite a bit too, especially after long runs where it's often difficult to hydrate enough to make up for water losses.  Make sure you measure your body fat first thing in the morning after going to the bathroom and before eating or drinking anything.  Otherwise, the results will be inaccurate.  Also, make sure to buy one with "Athlete Mode" or else it will overestimate your body fat.  Tanita BF-680W is a great choice.

To answer your debate, I can tell you that water retention is only temporary and would not account for your thighs growing in size.  It could be muscle growth, more body fat (women tend to accumulate in the thighs), or a combination.  Women that have greater amounts of testosterone are more likely to build muscle than other women.  But its not chronic water retention, w/o a doudt.

Unfortunately, the changes have already happened and it is pure speculation on the cause at this point.

Hope this helps a bit...a mystery for sure.

Larry