Approximately 25% of individuals on anti-depressants, including those in the SSRI classification, such as Lexapro, will demonstrate a 10+ pound increase in weight over time. This side effect did not appear in trials of anti-depressants, as most trials were limited to 12 weeks.
There are a number of theories as to why antidepressants lead to weight gain, and this includes both an increase in appetite, as well as a lowered metabolism.
I am on Celexa, Lexapro's sister drug, and I am seeing a gain in weight. I am looking at both reducing my caloric intake, and increasing my activity to offset this.
The very best to you, Shardeni!... Chuck
P.S.: I laughed when I read about Ian weighing-in!