Gerbil Weight Gain

Question
My female gerbil is about two years old.  A few weeks ago, I noticed that she has gained weight around her waist area (weight looks evenly distributed on both side).  She looks like she has swallowed a golf ball and there has been no change in her routine (eating, sleeping, social).  Does this sound like something I should be worried about?  

Answer
Dear Olga,
thank you for yor question.
If you can rule out a pregnancy, I would definitely see a vet with her. It's possible that she has an internal tumor.
Usually, gerbils that are just fat look different, they don't have the golfball-look you describe. So I think it would be best to rule out a health problem. Here's a list of good gerbil vets:
http://gerbilforum.proboards.com/index.cgi?board=vet
I hope I was of some help to you
Jennifer