The evaluation of breast milk intake is of particular importance for setting future breast-feeding recommendations and to investigate success strategies for breastfeeding promotion. Exclusive breastfeeding during the first 6 months of an infant’s life is an important factor for optimal growth and health of the child. Moreover, the assessment of postpartum changes in maternal body composition provides important information. In Morocco, this is the first time that breastfeeding practices and human milk intake have been quantified, and that changes in maternal body composition postpartum have been assessed. This study included 32 mother-baby pairs. The exclusive breastfeeding rate, intake of human milk and water from other sources, and the body composition of the mothers were measured at 1st, 3rd and 6th month postpartum by using the deuterium oxide dose-to-mother technique. Results showed that the exclusive breastfeeding rate was 33.3% at the first month, 26.7% at the third and 12.5% at the sixth. Mean intake of breast milk was 615.6 g/d, 741.9 g/d and 843.6 g/d at 1, 3 and 6 months respectively. As expected, there was a significant change in the mothers’ body composition between the first and sixth months. As a proportion of body weight, fat free mass increased by 13.4% and fat mass decreased by 33.4%. In conclusion, the rate of exclusive breastfeeding in Morocco remains low, despite advice on the benefits of breastfeeding, clearly showing a resistance to change the behavior of these mothers.