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

A poor diet can lead to a lack of vitamins, minerals, and other essential substances.

Malnutrition is characterized by a deficiency in the diet.

People can eat too much of 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 it can affect older people, those who consume excessive amounts of alcohol, and people who do not eat fresh fruits and vegetables.

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

According to the World Health Organization (WHO), 462 million people around the world 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 can 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 absorbing nutrients in the correct way.

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

Globally, it contributes to 45 percent of deaths of children under 5 years of age.


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 easily.

Eventually, there may be respiratory failure 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, there can be long-term effects on mental function, and digestive problems can persist. In some cases, these can be for life.

Severely malnourished adults that began in adulthood usually make a full recovery 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 is the result of a diet that lacks energy and protein due to a deficit in all the major macronutrients, such as carbohydrates, fats, and proteins.

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

The functional and structural abnormalities associated with primary protein-energy malnutrition are often reversible with nutritional therapy.

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

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 premucosal (maldigestion), mucosal (malabsorption) or postmucosal ( 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, acquired immunodeficiency syndrome (AIDS), and rheumatic diseases, are characterized by the involuntary loss of body weight and muscle mass in the context of a 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 greater loss of muscle tissue observed in these patients than in those with starvation or pure semistarvation.

Restoration of muscle mass is unlikely with nutritional support unless the underlying inflammatory disease is corrected.

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

Critically ill patients show marked metabolic disturbances, manifested by increased energy expenditure, impaired endogenous glucose production and 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) that is 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 a lot of 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 retention of water in body tissues), which makes them appear bloated.

They are weak and irritable, and 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 serious 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 certain vitamins to complete starvation.

Marasmus is one of the most serious forms of protein-energy malnutrition (PEH) in the world.

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

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 recurrence.

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

Malnutrition due to 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 a large proportion of children under the age of five in poor 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 clearest symptom is a swelling of the thyroid gland called a goiter and affects around 780 million people worldwide.

But the most serious 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

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 per year.

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

Lack of iron

Iron deficiency, or sideropaenia, 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 key 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.

Very low 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.

There are several mechanisms that control human iron metabolism and protect against iron deficiency. The main 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 called latent iron deficiency or iron-deficient erythropoiesis.

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

Anemia is a condition characterized by 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), which is 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 be the result of 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 also in the elderly (ie, 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 for the conversion of the thyroid hormone thyroxine (T4) to its more active counterpart, triiodothyronine, and 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 that can be 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 and tooth loss, and eventually 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 time to onset of scurvy symptoms in unstressed adults on a completely vitamin C-free diet can vary from one month to more than six months, depending on the previous vitamin C load.

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

These studies found that all the obvious scurvy symptoms previously induced by an experimental scurvy diet with extremely low vitamin C content could be completely reversed with additional vitamin C supplements of just 10 mg per day.

Niacin or vitamin B deficiency

Niacin deficiency is currently 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.

It is for this reason that the population of these countries that consume corn as tortillas is not at risk of suffering from this deficiency.

Mild niacin deficiency has been shown to decrease 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 greater 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, which makes 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 that can range 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, and especially water.