Some assume that malnutrition and undernutrition are the same. This is not true. Undernourished refers to people who are not as tall as they should be for their age. Their weight is also lower than other people their age. Those who are undernourished may also look like they are wasting away because they are dangerously thin.
Overnourished people, on the other hand, may not always look like they are not getting enough nutrition. Yet, when their health is checked, there would be signs that they are not as healthy as they should be. Malnutrition is the term used not only for those who are undernourished but also those who are overnourished.