I lose a lot of weight BF, with my first I had dropped 2 dress sizes by the time I stopped, I didn't look very healthy though it honestly felt like he drained the life from me, my appetite never really increased but he fed around the clock, he was 20lb before I even started solids at 6 months.
I haven't noticed as much of a difference this time around, but he doesnt feed barely at all and is a smaller baby, I've also been eating a lot more this time (giving birth at xmas didn't help!!) I am back to my pre pregnancy size though and was almost straight away.
I'm starting back at the gym next week though as I am mindful I will probably put weight on once I stop BF.
It makes your metabolism 3 times faster on average, but we can get increased appetites as well so it'll affect women differently.