Malnutrition refers to deficiencies, excesses, or imbalances in a person's intake of energy and/or nutrients.

• Undernutrition: Includes stunting (low height for age), wasting (low weight for height), underweight (low weight for age), and micronutrient deficiencies (lack of important vitamins and minerals).
• Overnutrition: Includes overweight, obesity, and diet-related noncommunicable diseases (such as heart disease, stroke, diabetes, and some cancers).

Malnutrition can result from a variety of factors, including inadequate food intake, poor nutrient absorption, and underlying diseases. It can affect people of all ages, but is particularly harmful to young children and pregnant women.

According to the World Health Organization (WHO), malnutrition encompasses both undernutrition and overnutrition.