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What is Malnutrition?

In this article, you will explore the major forms of malnutrition, how they are caused and what can be done to treat them.

Most people have seen the shocking images of severely malnourished children with stick-thin arms, ribs sticking out and a bloated belly. Malnutrition can present itself in different forms though, even overnutrition or obesity can be considered as a form of malnutrition.

Undernutrition is definitely not limited to low-income countries and overnutrition to high-income ones, in fact they are the two biggest global burdens of disease and both are spread all over the globe. 1.9 billion adults are obese or overweight and 462 million underweight.

In this article, you will explore the major forms of malnutrition, how they are caused and what can be done to treat them.

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

What forms of malnutrition exist?

  • Undernutrition, a deficiency of calories or specific nutrients
  • Micronutrient-related malnutrition, that includes deficiencies such as vitamins and minerals or micronutrient excess.
  • Overnutrition, an overload of nutrients, leading to obesity and noncommunicable disease.

Although undernutrition and overnutrition seem opposites, they can coexist, known as the double burden of malnutrition or even the triple burden in case of micronutrient deficiency on top.

Monotonous diets can for instance cause excess of carbohydrates and sometimes fat as well as a deficiency in micronutrients and protein. In low and middle-income countries where undernutrition is more common, obesity is also rapidly rising, leading to combined under- and overnutrition within individuals, households and populations.

In western countries low muscle mass as a sign of undernutrition is also seen in individuals with obesity. These combinations require more extensive tools for diagnosis, as described below.


Let’s take a closer look at undernutrition first. Not having enough food has been a major challenge of mankind throughout history and it still is today. Especially elderly and also children with their increased demand for nutrients are at risk.

Undernutrition is a directly or indirectly contributing factor in 45% of deaths in children under the age of 5 years old. In children two major forms of severe malnutrition are distinguished, marasmus and kwashiorkor. The latter is caused by a monotonous carbohydrate-based diet that does not contain enough protein, such as diets composed of almost only rice or maize.

Marasmus is due to a deficiency of calories in general, including protein. Key kwashiorkor symptoms include loss of muscle mass, an enlarged belly, swollen limbs due to edema and reduced height-for-age (or stunting). Main signs of marasmus are low weight-for-height (or wasting), very thin limbs with little muscle as well as fat and therefore visible bones, dry skin and brittle hair.

A lack of high-quality food obviously drives undernutrition, yet in high-income countries with a stable availability of nutritious foods, undernutrition is also an issue, especially among elderly. It can be as high as 50% in elderly homes.

Medical conditions are also a major cause of undernutrition at all ages. As undernutrition hinders recovery from disease in general, many hospitals routinely screen for it. Its cause is often a combination of biological, medical and behavioral factors described as the nine D’s: dementia, depression, disease, dysphagia (swallowing issues), dyseusia (less taste), diarrhea, drugs, dentition (e.g. bad teeth) and dysfunction, for instance no appetite due to loneliness.

Micronutrient deficiency

Micronutrients enable the body to produce enzymes, hormones, and other substances that are essential to maintain health and support growth. With enough variety in your diet, micronutrient deficiencies are unlikely.

Nevertheless, 2 billion people are affected by hidden hunger worldwide. Especially iron, but also iodine, folate, vitamin A, and zinc deficiency are common. Insufficient iron is an important factor for having too little red blood cells that occurs in more than 30% of the world population and is the only common micronutrient deficiency in high-income countries.

Pregnant women and children are most at risk. As animal products are micronutrient-rich, plant-based diets carry more risk of deficiencies in iron, zinc and vitamin B12.


The obesity pandemic and chronic diseases are threatening healthcare systems everywhere. All the processed energy-dense food around, forms a constant temptation in our environment to overload ourselves with fats and sugars.

We learn to like the taste of these nutrients as a newborn, yet as adults we no longer need all those calories. Many of us also don’t need to be physically active anymore to obtain a meal and thereby burn excess calories. Poor nutrition and lack of physical activity are the major contributors to an unhealthy lifestyle, followed by sleeping patterns, stress and inadequate financial resources.

Genetics and knowledge on how to live a healthy life are factors as well. Our physical and social environment strongly affect our food choices. Most of us have learned how to eat from our parents and our food habits are strongly connected to cultural habits. It’s no surprise therefore that persistent problem of obesity often clusters together in neighborhoods.

How is malnutrition diagnosed?

  • The most basic form of diagnosis is through measuring weight and height combined with general appearance of the patient, especially for undernutrition (i.e. the above symptoms). Low weight-for-height often indicates a recent weight loss in children, whereas low height-for-age often occurs over a longer period of time and unintentional weight loss within 3-6 months is an important indicator for all ages.
  • Body mass index (BMI) is also an important indicator of undernutrition and of obesity. To measure signs of undernutrition such as low muscle mass in obese individuals requires imaging techniques such as MRI or CT. Micronutrient deficiencies can be measured by a laboratory in blood.
  • For screening of undernutrition in hospitals for instance, there are several screening tools, such as the Nutritional Risk Screening 2002 (NRS2002) and Malnutrition Universal Screening Tool (MUST) that combine the above basic measures.


When treating undernutrition, it is important to slowly increase the amount of nutritious food and replenish the nutrients that are lacking, possibly also with supplements for micronutrients.

Therapeutic milk is often used, F75 for the stabilization phase, followed by F100 for the rehabilitation phase. Ready to use therapeutic foods have saved millions from malnutrition, especially in low-income countries as it can be stored and shipped unrefrigerated.

Treatment of overnutrition starts with an attempt to stimulate lifestyle changes that includes education on a healthy eating pattern. However, it routinely focuses on the underlying chronic disease that often comes with it to lower blood sugar levels in case of diabetes and blood lipid levels as well as blood pressure to treat cardiovascular risk. In extreme cases bariatric surgery is the ultimate treatment.

What we would like you to reflect on

  • How do you make sure to maintain enough variety in your diet?

Author: Dr. Tim van Zutphen

© University of Groningen
This article is from the free online

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