1oz breast milk = 20 calories burnt. Wellllll, I'm nursing AND pumping and last week I used a scale to determine how much my son was eating at a time. He's eating 4 ounces at a time, 8 times a day...so that's 32 ounces. I'm also pumping 4 times a day and getting 6 oz at a time. Soooo that's 56ish ounces a day. 1,120 calories a day and I've only been eating 1,400 at most. This explains why I thought I was dying. Lol. Just thought I'd share because I hadn't realized just how much it takes to nurse/pump.