What’s the difference between malnutrition and undernutrition, and why is it important?

Malnutrition is an umbrella term for poor nutrition, whether that is excess consumption of nutrients (overnutrition) or inadequate consumption or absorption of one or more nutrients (undernutrition). The three broad groups of conditions under the term ‘malnutrition’ are:

• undernutrition
• micronutrient-related malnutrition (e.g. lack of vitamins); and
• overnutrition, which can lead to obesity and diet-related diseases (such as heart disease, stroke, diabetes and cancer).

Malnutrition affects billions of people worldwide, with vulnerable groups such as children and pregnant women being most significantly impacted.

Find out more about malnutrition here.

Undernutrition is a deficiency of calories or of one or more essential nutrients. It is caused by not having enough to eat or having a diet that lacks proper nutrition or food variety (i.e. calories or energy, protein, or other vital vitamins and minerals), or being unable to properly absorb nutrients from the food one eats to sustain good physical and mental health, for example through illness. Undernutrition is often obvious: people look underweight, bones often protrude, their skin is dry and inelastic, and their hair is dry and falls out easily.

When individuals are undernourished, they can no longer maintain natural bodily functions, such as growth, resisting infections and recovering from disease, learning and physical work, and pregnancy and lactation in women. Undernutrition makes children in particular much more vulnerable to disease and death.

There are four broad sub-forms of undernutrition: wasting, stunting, underweight, and deficiencies in vitamins and minerals.

• Low weight-for-height is known as wasting. It usually indicates recent and severe weight loss, because a person has not had enough food to eat and/or they have had a disease, such as diarrhoea, which has caused them to lose weight.
• Low height-for-age is known as stunting. It is the result of chronic undernutrition. Stunting can negatively affect a child’s brain function, organ development, and immune system and holds them back from reaching their full potential.
• Children with low weight-for-age are known as underweight. A child who is underweight may be stunted, wasted, or both.

Worldwide in 2022, an estimated 148.1 million children under five years of age were stunted, 45 million were wasted and 37 million were overweight. 

Undernutrition is most common among families in low and middle-income countries. Certain conditions increase the risk of undernutrition. For example:

• Being very poor
• Being homeless
• Having psychiatric disorders
• Disease  (being ill may make people unable to eat enough food because they have lost their appetite or because their body’s need for nutrients is greatly increased)
• Age (infant, children, and adolescents are at risk of undernutrition because they are growing and therefore need a lot of calories and nutrients)

In some parts of the world, food supplies are inadequate because of war, drought, flooding, or other factors.

Hunger and malnutrition usually go hand-in-hand. People suffer from hunger because they don't get enough food, and not getting enough food over the long term can lead to malnutrition. However, there is no guarantee that an abundance of food will stamp out malnutrition. In other words, food security and nutritional security are two different things. Malnutrition relates to the quality of the diet, and the inadequate intake of nutrients and proteins.

We work towards the survival and wellbeing of the world's most vulnerable communities, while ensuring they obtain the knowledge and resources to keep themselves and their families healthy and nourished. We do this through both curative and preventative approaches.

Check out just some of the ways our health and nutrition programming is helping to change lives around the world.