Malnutrition can mean undernutrition or overnutrition. Undernutrition occurs when the body doesn't get enough nutrients. Overnutrition comes from taking in excess calories. Overnutrition with too many calories but a low level of nutrients is a common cause of malnutrition. Causes of undernutrition include lack of available or healthy food, a poor diet, digestive conditions, or another disease.

Symptoms of undernutrition are fatigue, dizziness, weight loss and slow growth. Children with overnutrition are at risk of developing a wide range of complications related to the extra weight. Untreated malnutrition can cause physical or mental disability.

Treatment for malnutrition must address social disparities in access to healthy food and any underlying conditions as well as replace missing nutrients.