This is completely normal, and no, you haven't gained a pound of fat, nor a pound of muscle. :) Building muscle takes months or years, and cannot be done at a calorie deficit; that old saw is a bit of a math.
What's happening is the increased demands you're placing on your muscles is causing them to retain water. This is totally normal, and will even out. This is one reason it takes as much as 6-8 weeks for healthy lifestyle changes to show up on the scale, particularly when adding exercise.
Here's the SP expert answer on the subject: www.sparkpeople.com/community/ask_the_expe
Edited by: DRAGONCHILDE at: 2/4/2013 (12:50)