During breastfeeding, women are thin for the following reasons: 1, the most common reason is to bring the baby harder, as well as poor rest caused. In the process of breastfeeding, the first few months of the child’s work and rest time is not too regular, if the mother frequently get up to feed, and poor sleep, it will easily lead to weight loss. 2, insufficient nutritional intake, in the process of breastfeeding, the mother to provide a lot of nutrition for the baby, if the nutrition is not good during breastfeeding, it will lead to significant weight loss of women. 3, also need to exclude consumptive disease, like diabetes or hypothyroidism, etc., and hyperthyroidism, which require a visit to the endocrinology department.