medications can definately cause an increase or decrease in appetite. You should speak to the doctor that perscribed the meds and tell him/her that you are having this reaction.

A noted side effect of Klonopin is increased appetite. Lexapro increases the seratonin production in your brain, and that may effect your appetite as well (though typically it would decrease it, not increase it).

This could be a temporary reaction until your body adjusts. But if it is as extreme as you say, you really should tell your doctor.