Impaired health caused by a dietary deficiency, excess, or imbalance. To support human life, energy (from fat, carbohydrate, and protein), water, and more than 40 different food substances must be obtained from the diet in appropriate amounts. Malnutrition can result from the chronic intake of any of these substances at levels above, as well as below, ranges that are adequate and safe, but commonly, the term refers only to deficient intake.