Re: weight loss and bf
Everyone is different.
I personally (as did my sister) have to stay about 20 lb. above my base weight while I am nursing or my milk supply drops RAPIDLY. As a matter of fact, I lose ALL my baby weight and get back to my pre-baby weight in the first 2 weeks post-partum...and then gain 20 lbs. between then and when the baby hits 6 months. It is weird. It has happened with every on of my 3 children...and then (without working out or anything) it drops in about 2-3 weeks after they wean. It is just my body's own homeostasis. My sister (who is even skinnier base-weight than me) had the exact same phenomenon with all 5 of her kids.
I have plenty of friends who were able to work out and lose weight and it not affect milk supply enough to be problematic.