Children can be underweight because they have a low weight in relation to their height and/or because they are short in relation to their age. Waterlow introduced the term wasted for children with a low weight-for-height (WFH), and stunted for those who have a low height-for-age [1]. Children suffering from acute food shortage become wasted as they lose weight, but their height remains constant, and wasting is often considered as reflecting an episode of acute malnutrition (AM). In contrast, stunting is regarded as a more chronic form of malnutrition. Although wasting can also be chronic, and linear growth stops in the case of AM, AM is often defined by wasting, more specifically by a WFH <–2 z-score of the World Health Organization (WHO) growth standard [2]. Moderate acute malnutrition (MAM) is defined by a z-score between –2 and –3, and severe acute malnutrition (SAM) is defined by a WFH <-3 z-score or a mid-upper arm circumference (MUAC) <115 mm (in children aged 6 to 60 months) or the presence of nutritional edema [3]. The MUAC-based definition of SAM was introduced to include children with a low MUAC, because these children are at high risk of death [4]. In programs that aim to prevent malnutrition-associated mortality, MAM is also often defined by a MUAC between 115 and 125 mm [5]. The cutoffs for MAM and SAM are convenient for establishing programs, but there is no abrupt change of the pathophysiology or of the associated risk around these cutoffs, and there is a continuum between SAM and MAM.