Breastfeeding is an extra 500 calories a day. You can get by without adding it if you diet on your own, but a lot of diet programs cut you
way down on calories. I know the 24 points I'd get on Weight Watchers without breastfeeding works out to roughly 1250 calories.
What I did right after having Linda was spend a couple of months just counting calories using
FitDay, and keeping it to between 1600 - 1800 calories a day, and that worked pretty well. Just generally speaking, I wouldn't want to go under 1600 calories a day anyway, because if you cut too low you run the risk of getting over-hungry and binging. I know this from experience.