I was terrified to go on anything for an anxiety problem I developed. My doctor put me on Lexapro 5mg and it's helped immensely. I've been on it for about 3 months and the first couple of weeks on it, I gained weight. The problem for me was that my anxiety will feel like my hypoglycemia symptoms, so when I feel that coming on, I eat sugar like crazy.
Well, the Lexapro made me even more anxious for the first week I took it (the doc said that is normal), so I felt like i had a bottomless hunger that I tried to stuff food in there to fill.
It thankfully leveled off and since then, I've only gained about 5lbs and it's held steady.
As for if it effects how weight loss works...well, I guess I'll find out! I've just now started getting serious again about working out and trying to eat better, so we'll see!!