The present study tests a recently developed nutrient -dense spread, ready-to use- therapeutic food (RUTF), which offers a potential solution to home based nutrition rehabilitation. The concept has previously been shown to work not only in therapeutic feeding of undernourished children in nutrition rehabilitation units in Malawi but also home based supplementation of undernourished children aged 42 to 60 months in Mangochi District, southern Malawi. In the present study the investigators will test the efficacy in growth promotion of this product when provided as a supplementary food to moderately underweight infants (defined as WAZ <-2) between 6 and 18 months of age.