Answer: It depends on how much you were eating in relation to your weight pre-pregnancy – but generally yes.
Breastfeeding women produce an average of 24 oz of milk during the first 5 months after delivery. This requires about 500 calories daily. Much of the increased calories usually come from an increased caloric intake, but a small portion of the increased energy demand is from stored fat in women who are not trying to lose weight.
Incidentally, pregnancy costs approximately 85,000 calories over 40 weeks, which averages to about 300 calories daily. The first trimester costs less than 100 calories daily and the bulk of energy required is in the final two trimesters.