I have been taking a low dose of sertraline for some time now, and I have lost a significant amount of weight. I know it is an antidepressant, but they told me it would help with my anxiety that I seem to have a lot of. At the time I started I was really concerned with it causing weight gain, but it went in the right direction for me. I cannot say that it helped weight loss because at the same time I started the sertraline I also started seriously dedicating myself to regular exercise and cut out carbs.
In regards to the other part, for the first little while (I am guessing a couple months) I really had to work A LOT harder to let's say "reach the finish line". After a while though, things returned to normal.