Why does it take 2 weeks to gain 7 pounds but 2 months to lose that same 7 pounds?

As much as I love to travel, it is always nice to come home.

We got home Monday and yesterday, I decided to try to turn the heat up on my elliptical workout a little bit.  I spent 30 HARD minutes and then went out to run.  Now, before I tell you what happened in the run, understand that during the morning, I did something really stupid - I didn't eat anything and I didn't drink anything.  There was virtually nothing in my stomach.  Sooooo, the body was running pretty much on empty.

During the run, about half a mile in, I felt my CALF begin to cramp.  I immediately shut down, and walked home.  When I look back on my cramping, a lack of liquids and food seem to be a common denominator.  No food, a little dehydrated calf cramps.  No food, a little dehydrated calf cramps.  No food, a little dehydrated calf cramps.  Repeat. Repeat.

Today, I'm going to try the drink, eat something trick before I run.  Every other day running will continue, elliptical every day will continue, but the daily running won't.

One other thing that I forgot to mention.  While on vacation, I ate every meal like it was my last.  I turned down food only when I was too full to continue - popcorn, chips, crabs, beer, pretzels, candy,  pizza,  junk.  Vacations were meant for indulgence and I indulged.  And yes, I paid the price.  Plus 7 pounds.

Why does it take two weeks to put on 7 pounds but 2 months to take 7 pounds off?