I've been on lexapro (escitalopram) 10mg for 7 yrs for anxiety & gained 40lbs from it. i'm about to switch to zoloft 25mg. side effects from switching? weight loss?

Cross titration: Zoloft and Lexapro (escitalopram) are both metabolized by the same pathway. As such, a cross titration is usually recommended to avoid any adverse effects. As a side note, that's a pretty low dose of Zoloft -- so you might not achieve an adequate response. If this happens, don't hesitate to increase the dose (with your doctor of course). Hope that helps!