What is the difference between undernutrition and malnutrition?

While the terms are often used interchangeably, they have distinct meanings in the context of nutrition.

Malnutrition is a broad term referring to the impaired physical function that results from a prolonged deficiency, imbalance, or excess of total energy or specific nutrients, such as protein, vitamins, or minerals. It can be caused by an inadequate diet, poor eating habits, or a physical inability to properly absorb or metabolize nutrients due to metabolic defects or chronic illness. Because it encompasses both deficiencies and excesses, malnutrition can also result from the overzealous use of dietary supplements or unwise food choices.12

Undernutrition is a specific form of malnutrition characterized by a deficiency of energy or nutrients. It occurs when there is insufficient food intake to meet the body's energy needs, often leading to weight loss, muscle wasting, and a failure to thrive. Chronic undernutrition is a significant global health issue, frequently manifesting as protein-energy malnutrition (PEM), which includes conditions like marasmus and kwashiorkor.234

In short, while all undernutrition is a form of malnutrition, malnutrition is a wider category that also includes issues related to nutrient excess or imbalance.2