What to do when the weight starts creeping up again

You've lost weight, congratulations!  Your clothes are looser, you're feeling better, you're in a new healthier routine, then BOOM...you notice the scale starting to inch up again.  What's wrong?  Here are few reasons why the scale might not be cooperating:

1. You're weighing yourself too frequently.  Your weight will fluctuate 2-5 pounds on a normal basis, even throughout a single day.  This is mainly due to how much water you body is retaining. Try to avoid weighing yourself too frequently.  Ideal is once a week (the same day and time), but if it helps your accountability and you can take some daily ups and downs, weigh yourself first thing in the morning each day.  
2. You need to adjust your caloric intake.  As you lose weight, you need to adjust you daily caloric intake from time to time.  Not every week, but perhaps once for every 5-10% of body weigh you lose, and definitely when you get down to your target weight.  I posted some guidelines for doing this in a previous post.
3. You're gaining muscle.  Probably not likely, but if you are doing some serious strength training this might be a factor.  Muscle does weigh more than fat, so your fat loss might be offset by a gain in muscle.
4. You've gotten lax in your routine.  This is the most likely explanation. You had a vacation, got really busy at home or at work with some project, got sick, etc.  Some disruption to your normal eating and exercise routine.  Don't panic.  You haven't fallen off the bandwagon, you're not going to reverse all of the wonderful changes you have made.  This is normal, and it happens to everyone.  On a weekly basis, it's ok to have a cheat meal or two and you probably won't notice any effect.  But if you start having cheat days or weeks, you'll notice. Indulging in treats and unhealthy food will bring back cravings that you thought you had lost.  You need to pause, take a deep breath, remind yourself that you know how to eat right and exercise, and remember your commitment.  Don't beat yourself up, just start making better choices and keep moving forward.  
5. You need to change your exercise routine.  After a few weeks, your body can get used to a particular exercise regimen and your results might diminish.  You need to continue to exercise the same muscle groups, but adopt different exercises to shake your body out of complacency.  
6. You need to look at other measurements of progress.  An increasing weight can be a little concerning, but take a look at the bigger picture.  Have your body fat percentage measured.  Take your measurements.  See if your clothes are feeling tight or loose. Ask yourself how you are feeling in general.  There is more to being thin and healthy than just what the scale says.
7. You might need to rethink your goals.  If you are at a reasonably healthy weight and body fat percentage, you might be shooting for a unrealistic goal and your body is fighting you.  Check out my post on planning.  Shooting for a target weight that is too low for your age, gender and height can be as bad as being somewhat overweight. Perhaps it is time to just continue to exercise, eat well and let your body settle on a weight that it is comfortable with.  Be happy and content with that.

Remember, you're in this for life, not just temporarily.  Weight goes up and down, that is normal.  If it's going up for the wrong reasons (you're not paying attention to your health), recommit yourself and start moving forward again.