Weight retention after pregnancy contributes to increasing rates of obesity. There is evidence that breastfeeding is accompanied from changes in fat mobilisation and fat mass, nevertheless there are no data on the effects of breastfeeding on appetite-regulation. This study aims to investigate the direct effect of breastfeeding on the systemic levels of appetite-regulating hormones: ghrelin and PYY. Blood samples will be obtained at five time points (before, during and after breastfeeding) in ten mothers of healthy infants who breastfeed on demand and in ten mothers of healthy infants who do not breastfeed. All mothers will be fasting since 4 hours. The results will bring information on a possible direct effect of breastfeeding on appetite-regulatory hormones.