Types of Malnutrition: Classification, Effects, Impact and Prevention for a Healthy Life

A poor diet can lead to insufficient vitamins, minerals, and other essential substances.

A deficiency in the diet characterizes malnutrition.

People can overeat the wrong type of food and become malnourished. However, malnutrition also exists when a person lacks nutrients because they are not consuming enough food.

Too much protein can cause kwashiorkor, the symptoms of which include a distended abdomen.

Scurvy is rare in industrialized nations but can affect older people, those who consume excessive alcohol, and those who do not eat fresh fruits and vegetables.

Some babies and children on a limited diet may be prone to scurvy for whatever reason.

According to the World Health Organization (WHO), 462 million people worldwide are undernourished, and stunted development due to poor diet affects 159 million children worldwide.


Malnutrition during childhood can lead not only to long-term health problems but also to educational challenges and limited job opportunities in the future.

It can also delay recovery from injuries and illnesses and complicate diseases such as measles, pneumonia, malaria, and diarrhea. It can leave the body more susceptible to disease.

However, in some cases, malnutrition may be due to a health problem, such as an eating disorder or a chronic illness that prevents a person from correctly absorbing nutrients.

According to the World Health Organization (WHO), malnutrition is the most severe threat to global public health.

Globally, it contributes to 45 percent of deaths of children under five.


In children, adults, and especially pregnant women, starvation and malnutrition have a devastating impact.

Some of the symptoms that people with malnutrition can present include:

  • Lack of appetite or disinterest in food or drink.
  • Tiredness and irritability
  • Inability to concentrate
  • Constant cold.
  • Loss of body tissue, fat, and muscle mass.
  • Higher risk of getting sick and taking longer to heal.
  • Longer healing time for wounds.
  • Increased risk of complications after surgery.
  • Depression.
  • Fertility problems
  • Reduction of sexual desire.

In more severe cases:

  • Breathing becomes difficult.
  • The skin can become thin, dry, inelastic, pale, and cold.
  • The cheeks appear hollow, and the eyes sunken as the fat disappears from the face.
  • Hair becomes dry and sparse, falling out quickly.

Eventually, there may be respiratory and heart failure and the person may stop responding. Starvation can be fatal if it lasts 8 to 12 weeks.

Children may show a lack of growth and may be tired and irritable.

Behavioral and intellectual development can be slow, possibly resulting in learning difficulties.

Even with treatment, the mental function can have long-term effects, and digestive problems can persist. In some cases, these can be for life.

Severely malnourished adults that began in adulthood usually recover fully with treatment.


Each form of malnutrition depends on the nutrients that are lacking in the diet, for how long, and at what age:

Protein-energy malnutrition

The most basic type is called protein-energy malnutrition. It results from a diet lacking energy and protein due to a deficit in all the primary macronutrients, such as carbohydrates, fats, and proteins.

Primary protein-energy malnutrition is caused by a lack of access to adequate nutrient intake and generally affects children and the elderly.

Nutritional therapy often reverses the functional and structural abnormalities associated with primary protein-energy malnutrition.

However, prolonged primary protein-energy malnutrition can cause irreversible organ function and growth changes.

Secondary protein-energy malnutrition is caused by diseases that impair appetite, digestion, absorption, or metabolism of nutrients and can be divided into three general but often overlapping categories:

  • Diseases that affect the function of the gastrointestinal tract.
  • Attrition disorders.
  • Critical illness

Gastrointestinal disease can cause protein-energy malnutrition due to mucosal (maldigestion), mucosal (malabsorption), or most mucosal ( lymphatic obstruction ) defects.

The nutritional status of patients with protein-energy malnutrition caused by gastrointestinal tract dysfunction can often be restored to normal if adequate nutritional support can be provided through dietary manipulations, enteral tube feeding, or parenteral nutrition.

Wasting disorders, such as cancer, and acquired immunodeficiency syndrome (AIDS), and rheumatic diseases, are characterized by the involuntary loss of body weight and muscle mass in chronic disease.

These patients often experience wasting due to inadequate nutrient intake related to anorexia and possibly gastrointestinal tract dysfunction and metabolic abnormalities caused by alterations in regulatory hormones, cytokines, and systemic inflammation.

Alterations in metabolism are responsible for the more significant loss of muscle tissue observed in these patients than in those with starvation or pure semistarvation.

Muscle mass restoration is unlikely with nutritional support unless the underlying inflammatory disease is corrected.

Weight gain after nutritional support is generally caused by increased body fat and water mass, without significant increases in muscle tissue.

Critically ill patients show marked metabolic disturbances, increased energy expenditure, impaired endogenous glucose production, lipolytic rates, and protein degradation.

Therefore, protein and energy needs are increased in critically ill patients.

However, providing aggressive nutritional support can improve but does not prevent net loss of lean tissue without correcting the underlying disease or injury.


It is a disease caused by a lack of protein in a child’s diet.

It is a type of protein-energy malnutrition (PEM) widespread throughout the developing world.

Babies and children who grow up in tropical or subtropical areas (such as Africa, Asia, and South America) where there is much poverty are at risk for kwashiorkor.

The term “kwashiorkor” comes from a word used in Ghana that means a “disease of a baby deposed from the breast when the next is born.”

Kwashiorkor generally occurs when a baby is weaned from protein-rich breast milk (for whatever reason) and switched to low-protein foods.

In impoverished countries, protein-rich foods are hard to come by.

Children with kwashiorkor suffer from edema (excessive water retention in body tissues), making them appear bloated.

They are weak and irritable; in many cases, their skin pores and hair lose their shine and color.

If left untreated, kwashiorkor causes an enlarged liver, fluid loss (dehydration) from the bloodstream, even when the child has edema, stunted growth, and severe infection due to a weakened immune system.

It can also cause jaundice, drowsiness, and a low body temperature.


Marasmus is a severe form of malnutrition that involves the chronic loss of fat, muscle, and other tissues in the body.

This lack of nutrition can range from a shortage of specific vitamins to complete starvation.

Marasmus is one of the world’s most severe forms of protein-energy malnutrition (PEH).

Marasmus is a severe problem and is most common in children in underdeveloped regions, such as Africa, Latin America, and South Asia, where poverty, inadequate food supplies, and contaminated water are prevalent.

Contaminated water can contain bacteria or parasites that enter the body when the water is consumed and cause infections that complicate the condition.

The symptoms of marasmus will vary depending on the severity and whether there are associated infections or other conditions.

General symptoms of marasmus include chronic diarrhea, dizziness, fatigue, and rapid weight loss.

If the disease is caused solely by poor nutrition, then a change in diet should be enough to correct the problem and prevent a recurrence.

Marasmus that is related to an underlying disease may require additional treatment.

Malnutrition is due to a lack of micronutrients.

Micronutrient malnutrition involves a moderate to severe lack of vitamins A, B, C, and D, calcium, folate, iodine, iron, zinc, and selenium.

These vitamins and minerals are of utmost importance in various bodily processes, and their deficiency can make an otherwise healthy person malnourished.

Lack of iron

It is the most common form of malnutrition worldwide and affects millions of people.

Iron forms the molecules that carry oxygen in the blood, so symptoms of a deficiency include tiredness and lethargy.

Iron deficiency also impairs cognitive development, affecting 40-60 percent of children ages 6 to 24 months in developing countries.

Vitamin A deficiency

It weakens the immune systems of many children under five in developing countries, increasing their vulnerability to disease.

The risk of dying from diarrhea, malaria, or measles can increase by 20 to 40 percent due to vitamin A.

It affects 140 million pre-school children in 118 countries and more than seven million pregnant women; it is also one of the leading causes of childhood blindness in developing countries.

Iodine deficiency

The most apparent symptom is a swelling of the thyroid gland called a goiter which affects around 780 million people worldwide.

However, the most severe impact is on the brain, which cannot develop properly without iodine.

According to a UN investigation, some 20 million children are born with mental problems because their mothers did not consume enough iodine.

The most affected person may suffer from cretinism, associated with severe mental retardation and physical atrophy.

Zinc deficiency

It contributes to growth failure and weakens immunity in young children.

It is linked to an increased risk of diarrhea and pneumonia, resulting in nearly 800,000 deaths yearly.

Anemia, immunity, and poor sensory perception can appear due to zinc deficiency.

Lack of iron

Iron deficiency, or sideropenia, is the state in which a body does not have enough iron (or not qualitatively enough) to meet its eventual needs.

Iron is present in all cells of the human body and has several vital functions, such as

  • carrying oxygen to the tissues of the lungs as a critical component of the hemoglobin protein,
  • acting as a transport medium for electrons within cells in the form of cytochromes,
  • facilitating the reactions of oxygen enzymes in various tissues.

Deficient iron levels can interfere with these vital functions and lead to morbidity and death. In blood plasma, iron is transported closely bound to the transferrin protein.

Several mechanisms control human iron metabolism and protect against iron deficiency. The primary regulatory mechanism is in the gastrointestinal tract.

When iron loss is not sufficiently compensated for by adequate dietary iron intake, a state of iron deficiency develops over time.

When this state is not corrected, it leads to iron deficiency anemia.

Before anemia occurs, the medical condition of iron deficiency without anemia is a latent iron deficiency or iron-deficient erythropoiesis.

Untreated iron deficiency can lead to iron-deficiency anemia, a common type of anemia.

Anemia is inadequate levels of red blood cells (erythrocytes) or hemoglobin.

Iron deficiency anemia occurs when the body lacks sufficient amounts of iron, resulting in reduced production of the protein hemoglobin.

It causes anemia and poor brain development.

Vitamin D deficiency

A diet deficient in vitamin D coupled with inadequate sun exposure causes osteomalacia (rickets when it occurs in children), a softening of the bones. In the developed world, this is a rare disease.

However, vitamin D deficiency has become a global problem in the elderly and is still common in children and adults.

Low blood calcifediol (25-hydroxy-vitamin D) may result from avoiding the sun.

The deficiency results in impaired bone mineralization and bone damage leading to bone-softening diseases, including rickets and osteomalacia.

Selenium deficiency

It leads to poor heart function, weak immunity, and osteoarthritis.

It can occur in patients with severely compromised bowel function, those receiving total parenteral nutrition, those who have had GI bypass surgery, and the elderly (i.e., over 90).

People dependent on food grown from selenium-deficient soils may be at risk of deficiency.

An increased risk of developing various diseases has also been observed, even when certain people lack optimal amounts of selenium but not enough to classify them as deficient.

Selenium is also required to convert the thyroid hormone thyroxine (T4) to its more active counterpart, triiodothyronine. As such, a deficiency can cause symptoms of hypothyroidism, including extreme fatigue, mental decline, goiter, cretinism, and miscarriage.

Vitamin C deficiency

Scurvy is a disease that results from a deficiency of vitamin C since, without this vitamin, the collagen produced by the body is too unstable to perform its function.

Brown spots on the skin, bleeding from all mucous membranes, and soft and spongy gums are symptoms caused by scurvy.

A person suffering from this ailment generally feels depressed, looks pale, is partially paralyzed, and the spots most commonly appear on the legs and thighs.

In advanced scurvy, there are open, festering wounds, tooth loss, and death.

The human body can store only a certain amount of vitamin C, so the body’s reserves are depleted if fresh supplies are not consumed.

However, the onset of scurvy symptoms in unstressed adults on a complete vitamin C-free diet can vary from one month to more than six months, depending on the previous vitamin C load.

Critical human dietary studies on experimentally induced scurvy were conducted on conscientious objectors during World War II in Great Britain and Iowa state prisoners in the late 1960s and 1980s.

These studies found that all the apparent scurvy symptoms previously induced by an experimental scurvy diet with shallow vitamin C content could be completely reversed with additional vitamin C supplements of just 10 mg daily.

Niacin or vitamin B deficiency

Niacin deficiency is most commonly seen in underdeveloped countries where poverty, chronic alcoholism, and malnutrition reign.

To himself, in undeveloped countries, where corn is mainly consumed (since this is the only digestible low-niacin grain), we can see that this deficiency is common.

Pretreatment with alkaline ingredients that increase the bioavailability of niacin when producing corn flour is known as nixtamalization.

This is why the population of these countries that consume corn as tortillas is not at risk of suffering from this deficiency.

Mild niacin deficiency has decreased metabolism, resulting in decreased cold tolerance.

A severe deficiency of niacin in the diet can cause pellagra disease, which is characterized by the appearance of symptoms such as hyperpigmentation, inflammation of the mouth and tongue, delusions, diarrhea, amnesia, digestive disorders, thickening of the skin, dermatitis, and dementia, as well as Casal’s collar injuries in the lower part of the neck and if not treated in time it can lead to death.

Anxiety, depression, restlessness, irritability, listlessness, and poor concentration are the most common psychiatric symptoms of niacin deficiency.

Alcoholic patients commonly have more excellent intestinal permeability, which causes poor health outcomes.

There is also an inherited nutritional disorder called Hartnup, which can lead to niacin deficiency.

This condition stems from a deficit in the kidneys and intestines, making it more difficult for the body to absorb and break down tryptophan (the amino acid used to synthesize niacin).

The result of this condition is similar to pellagra, including symptoms such as sensitivity to sunlight, a red rash, and scaly skin.

As a treatment for this condition, oral niacin is administered in doses ranging from 40 to 200 mg daily if identified and treated early.

Vitamin B12 deficiency

It leads to nerve degeneration and poor red blood cell formation.

Folate or vitamin B9 deficiency

It causes slow growth and anemia.


To prevent malnutrition, people need to consume a variety of nutrients from a variety of food types.

There should be a balanced intake of carbohydrates, fats, proteins, vitamins, and minerals, as well as plenty of fluids, especially water.