Undernutrition, already one of the world’s most serious health problems, is at risk of worsening as the global economy deteriorates. In poor countries, undernutrition is the largest single contributor of more than one third of all deaths of children under five years of age, many of which are preventable through effective nutrition interventions (Lancet, 2008). Thus, reducing undernutrition is vital for children’s survival, particularly in poor countries, and consequently for socio-economic development. Moderate malnutrition is associated with more nutrition-related deaths than severe malnutrition because moderate malnutrition affects a greater number of children. According to the World Health Organization (WHO), moderate malnutrition includes all children with moderate wasting, defined as a weight-for-height between –3 and –2 z-scores with reference to the WHO Child Growth Standards, and those with moderate stunting, defined as a height-for-age between -3 and -2 z-scores with reference to the WHO Child Growth Standards. Most of these children will be moderately underweight (weight-for-age between –3 and –2 z-scores). This symposium will focus on the management (prevention and treatment) of moderate wasting or moderate acute malnutrition (MAM). The importance of MAM should not be neglected. Although moderate wasting is not a condition of medical urgency, it can easily deteriorate. If some of these undernourished children with moderate wasting do not receive adequate support, they may progress towards severe acute malnutrition (SAM) — defined by the presence of severe wasting and/or bilateral pitting oedema — which is a life threatening condition. The provision of complementary food to prevent and treat moderate malnutrition among children under two years of age is also less costly (US $40–80 per child) than the treatment of SAM (US $200 per episode and per child). Therefore, the management of MAM should be a public health priority. Preventing MAM could go hand-in-hand with preventing stunting, especially when the focus is on ensuring consumption of nutritious complementary food in addition to breastfeeding between the ages of 6 and 23 months. In general, growth faltering takes place soon after birth and increases thereafter, reaching its lowest value close to two years of age; thus supporting the concept that the intrauterine period and the first two years of postnatal life are a critical window for preventing malnutrition. Therefore scaling up nutrition during the critical window of opportunity — the first 1000 days — can have a measurable impact on growth, development and incidence of chronic diseases. Although there is no need to feed moderately wasted children with therapeutic foods that are used to treat SAM, they require higher intake of energy and essential nutrients than non-malnourished children. Ideally, their dietary management should be based on the use of locally available macro- and micronutrient-dense foods, including breast milk where applicable. In settings with food shortage, specially formulated supplementary foods are used to facilitate the recovery of moderately wasted children. In 2008 and 2010, the WHO convened meetings on the dietary management of moderately malnourished children and on reviewing the evidence on strategies and programmatic approaches to manage moderate wasting. A technical note on the nutrient composition of supplementary foods for the management of MAM in infants and children aged 6–59 months was published by the WHO in 2012. Moreover, the Global Nutrition Cluster (GNC) of the Inter-Agency Standing Committee established a Task Force on Moderate Acute Malnutrition in 2011 to develop a decision-making tool which will support practitioners in the prevention and treatment of MAM in emergencies. This tool is currently being evaluated. However, more evidence on effective programmatic approaches to manage moderate wasting is needed. In the evaluation of interventions, functional and structural outcomes such as body composition should be included in addition to the traditional methods used to assess healthy physical, cognitive and psychomotor development. Accurate assessment of body composition to determine the nature of the weight gained (lean body mass and fat body mass) over time can provide key information for evaluating the efficacy and effectiveness of interventions, as well as for gauging the risk of chronic diseases. The International Atomic Energy Agency (IAEA) has been a leader in developing and promoting the use of standardized protocols for body composition assessment using stable isotope techniques. Such techniques provide sensitive means of assessing the impact of interventions on the quality of growth, i.e., lean vs. fat body mass accumulation. This key information can complement and contribute to global efforts in improving infant and child nutrition.