Gaining weight?

Ok, so I have been pretty consistant on my weight in the past 6 months, haven't gained. Last monday I started working out and lifting weights, I gained 5 pounds. Why, I'm eating the same? 

That could easily be muscle weight! Just wait it out for a little while...see if you notice yourself looking any heavier. Chences are if it's muscle weight you will look slimmer and toned.

Five pounds of muscle in a week?  I seriously doubt that.  More likely, it is retained water.  If you are exercising more and sweating, you may not be rehydrating enough afterwards and as a result are retaining water.  When you start a new exercise plan, you should look at adjusting your fluid intake and if you are eating exactly the same level of calories as you were before you started exercising, then your body could be adjusting to the change by hording nutrients.  Give it a few weeks to make the adjustment, then worry about weight gain/loss then.  During the transition, just focus on keeping properly hydrated and consider eating back at least part of the calories you are burning.  If you are eating exactly the same number of calories as before you started working out, then your deficit just changed and may be too drastic.

Original Post by klutzykels:

That could easily be muscle weight!

 It is completely impossible for that to be muscle weight. Read techdog's post.

you may be hydrating okay, but anytime you increase your activity level dramatically (or even change your routine a lot), your muscles tend to swell and hold onto some water.  ease into your program.  or just keep at it, and eventually the weight will go back to normal.

I remember when I was doing a lot of cardio and I would lose a little bit everyday, the day after I added weight training my weight shot up 2 pounds. Tis normal.