Not necessarily, it depends on who eat how much. My female is way fatter than my male is. And when they expel their water it's a defend mechanism they use to hopefully stop the “attach” on them.
Here's a picture of Vera (left) & Vern (right), and Vern is on the fatter side in this pic. He's usually much thinner.
Name:  Vern & Vera.jpg
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When was the last time Marven ate & pooped?