During breastfeeding, you should try to increase your caloric intake by about 300 calories a day, but it is critical that these extra calories are nutritious calories. (newkidscenter.com)
So, mothers may find themselves needing to increase their caloric intake while breastfeeding and an extra 300 - 500 calories is the recommendation. (lactationlink.com)
This will increase the caloric intake with little risk of gaining body fat. (fitnessandpower.com)