Malnutrition: causes, symptoms and treatments

Malnutrition: causes, symptoms and treatments

Malnutrition is a broad term which refers to both undernutrition (subnutrition) and overnutrition.

Individuals are malnourished, or suffer from undernutrition if their diet does not provide them with adequate calories and protein for maintenance and growth, or they cannot fully utilize the food they eat due to illness.

People are also malnourished, or suffer from overnutrition if they consume too many calories

Malnutrition can also be defined as the insufficient, excessive or imbalanced consumption of nutrients.

Several different nutrition disorders may develop, depending on which nutrients are lacking or consumed in excess.

According to the World Health Organization (WHO), malnutrition is the gravest single threat to global public health.1

What is malnutrition?

This text will focus more on the undernutrition aspect of malnutrition, rather than overnutrition.

Subnutrition occurs when an individual does not consume enough food. It may exist if the person has a poor diet that gives them the wrong balance of basic food groups.

Obese people, who consume more calories than they need, may suffer from the subnutrition aspect of malnutrition if their diet lacks the nutrients their body needs for good health.

Poor diet may lead to a vitamin or mineral deficiency, among other essential substances, sometimes resulting in scurvy - a condition where an individual has a vitamin C (ascorbic acid) deficiency.

Though scurvy is a very rare disease, it still occurs in some patients - usually elderly people, alcoholics, or those that live on a diet devoid of fresh fruits and vegetables. Similarly, infants or children who are on special or poor diets for any number of economic or social reasons may be prone to scurvy.

According to the National Health Service (NHS), UK, it is estimated that around three million people in the UK are affected by malnutrition (subnutrition).2

According to the Food and Agriculture Organization (FAO), the number of people globally who were malnourished stood at 923 million in 2007, an increase of over 80 million since the 1990-92 base period.3

List of countries by percentage of population suffering from undernourishment. (Source: United Nations)

The World Health Organization (WHO) says that malnutrition is by far the largest contributor to child mortality globally, currently present in 45 percent of all cases.4

Underweight births and inter-uterine growth restrictions are responsible for about 2.2 million child deaths annually in the world. Deficiencies in vitamin A or zinc cause 1 million deaths each year.

WHO adds that malnutrition during childhood usually results in worse health and lower educational achievements during adulthood. Malnourished children tend to become adults who have smaller babies.

While malnutrition used to be seen as something which complicated such diseases as measles, pneumonia and diarrhea, it often works the other way round - malnutrition can cause diseases to occur.

Globally, as well as in developed, industrialized countries, the following groups of people are at highest risk of malnutrition (subnutrition):

  • Elderly people, especially those who are hospitalized or in long-term institutional care
  • Individuals who are socially isolated
  • People on low incomes (poor people)
  • People with chronic eating disorders, such as bulimia or anorexia nervosa
  • People convalescing after a serious illness or condition.

Symptoms of malnutrition

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

Signs and symptoms of malnutrition (subnutrition) include:5

  • Loss of fat (adipose tissue)
  • Breathing difficulties, a higher risk of respiratory failure
  • Depression
  • Higher risk of complications after surgery
  • Higher risk of hypothermia - abnormally low body temperature
  • The total number of some types of white blood cells falls; consequently, the immune system is weakened, increasing the risk of infections.
  • Higher susceptibility to feeling cold
  • Longer healing times for wounds
  • Longer recover times from infections
  • Longer recovery from illnesses
  • Lower sex drive
  • Problems with fertility
  • Reduced muscle mass
  • Reduced tissue mass
  • Tiredness, fatigue, or apathy
  • Irritability.

In more severe cases:

  • Skin may become thin, dry, inelastic, pale, and cold
  • Eventually, as fat in the face is lost, the cheeks look hollow and the eyes sunken
  • Hair becomes dry and sparse, falling out easily
  • Sometimes, severe malnutrition may lead to unresponsiveness (stupor)
  • If calorie deficiency continues for long enough, there may be heart, liver and respiratory failure
  • Total starvation is said to be fatal within 8 to 12 weeks (no calorie consumption at all).


Children who are severely malnourished typically experience slow behavioral and intellectual development, which may lead to intellectual disabilities. Even when treated, undernutrition may have long-term effects in children, with impairments in mental function and digestive problems persisting - in some cases for the rest of their lives.

Adults whose severe undernourishment started during adulthood usually make a full recovery when treated.

On the next page we look at the causes of malnutrition and how it is diagnosed. On the final page we discuss treatments for malnutrition and how it can be prevented.

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