Malnutrition is the condition that develops when the body does not get the right amount of the vitamins, minerals, protein, and/or calories it needs to maintain healthy tissues and organ function.



Malnutrition occurs in people who are either undernourished or overnourished. Undernutrition is a consequence of consuming too few essential nutrients or using or excreting them more rapidly than they can be replaced.

Infants, young children, and teenagers need additional amounts of nutrients for proper growth, as do women who are pregnant or breastfeeding. Nutrient loss can be accelerated by diarrhea, excessive sweating, heavy bleeding (hemorrhage), or kidney failure. Nutrient intake can be restricted by age-related illnesses and conditions, excessive dieting, loss of appetite, food allergies, severe injury, serious illness, a lengthy hospitalization, or substance abuse.

The leading cause of death in children in developing countries is protein-energy malnutrition. This type of malnutrition is the result of inadequate intake of calories from protein (and often calories) and low intakes of micronutrients (vitamins and minerals). Children who are already undernourished can suffer from protein-energy malnutrition (PEM) when rapid growth, infection, or disease increases the need for protein and essential minerals. These essential minerals are known as micronutrients or trace elements.

Two types of protein-energy malnutrition have been described—kwashiorkor and marasmus. Kwashiorkor occurs with fair or adequate calorie intake but inadequate protein intake, while marasmus occurs when the diet is inadequate in both calories and protein.

Child suffering from malnutrition in Guatemala.

Child suffering from malnutrition in Guatemala.
(Edward Lettau/Science Source)

There are various degrees of undernutrition. UNICEF estimated in 2017 that 150.8 million children under age 5 years have their growth stunted (decreased) due to undernutrition every year. Another 50.5 million children experience wasting. Wasting is a decrease in physical vitality and strength and a decrease in mental functioning. An additional 20 million children suffer severe acute malnutrition that is potentially fatal. UNICEF estimated that each year about half of all deaths in children under the age of 5 are attributed to some form of malnutrition including underweight, suboptimal breastfeeding, and vitamin and mineral deficiencies. About 90% of malnourished children live in 30 countries, primarily in Africa and Southeast Asia.


Obesity is of increasing concern in developed countries. In these countries, especially the United States, nutritional deficiencies have generally been replaced by dietary imbalances or excesses associated with many of the leading causes of death and disability. Risk of overnutrition is increased by eating a diet high in fat, salt, and sugar. WHO estimated in 2016 that 1.9 billion people worldwide were overweight, of which 650 million were obese. Ironically, the number of overweight children in Africa and Asia is increasing rapidly while in the same countries other children are dying of complications of undernutrition.

Nutritional disorders can affect any system in the body and the senses of sight, taste, and smell. They may also produce anxiety, changes in mood, and other psychiatric symptoms. Malnutrition begins with changes in nutrient levels in blood and tissues. Alterations in enzyme levels, tissue abnormalities, and organ malfunction may be followed by illness and death.

Causes and symptoms


Poverty, lack of access to food, and lack of food variety are the primary reasons why malnutrition occurs throughout the world. Drinking water that carries infectious organisms that cause diarrhea and parasites that interfere with absorption of nutrients from the intestine complicate the problem of malnutrition in developing countries.

Loss of appetite is associated with the aging process. Malnutrition affects one in four elderly Americans, in part because they may lose interest in eating. Diseases such as dementia and Alzheimer's disease may cause elderly people to forget to eat. Other factors may include the loss of appetite as a side effect of certain medications or conditions such as depression.

There is an increased risk of malnutrition associated with chronic diseases, especially diseases of the intestinal tract, kidneys, and liver. Patients with chronic diseases such as cancer, HIV/AIDS, intestinal parasites, and other gastric disorders may lose weight rapidly and become susceptible to undernourishment because they cannot absorb valuable vitamins, calories, and iron.

People with drug or alcohol dependencies are also at increased risk of malnutrition. These people tend to maintain inadequate diets for long periods of time and their ability to absorb nutrients is impaired by the alcohol or drug's affect on body tissues, particularly the liver, pancreas, and brain.

People with eating disorders such as anorexia nervosa or bulimia may restrict their food intake to such extremes that they become undernourished. Binge eaters may be overnourished.

Some people with food allergies may find it difficult to obtain food that they can digest. In addition, people with food allergies may need additional calorie intake to maintain their weight.

Failure to absorb nutrients in food following bariatric (weight loss) surgery can cause malnutrition. Bariatric surgery includes such techniques as stomach stapling (gastroplasty) and various intestinal bypass procedures to help people eat less and lose weight. Malnutrition is, however, a possible side effect of bariatric surgery.


Unintentionally losing 10 pounds or more may be a sign of malnutrition. People who are malnourished may be very thin or bloated. Their skin is pale, thick, dry, and bruises easily. Rashes and changes in pigmentation are common. Hair is thin and falls out easily. Joints ache and bones are soft and tender. The gums bleed easily. The tongue may be swollen or shriveled and cracked. Visual disturbances include night blindness and increased sensitivity to light and glare.

Other symptoms of malnutrition include:

Malnourished children may be short for their age, thin, listless, and have weakened immune systems. Malnourished children tend to perform less well on mental tasks and academically than normally nourished children.


Malnutrition screening tools are used to assess patients at risk of malnutrition. There are a number of screenings available that a doctor may use to come up with a score that makes it easier to assess a patient's level of nutrition. Scoring a patient gives a baseline for which a doctor can monitor a patient's nutrition in subsequent medical examinations. These screenings are crucial to assessing malnutrition and treating it.

Overall appearance, behavior, body-fat distribution, and organ function can alert a family physician, internist, or nutrition specialist to the presence of malnutrition. Patients may be asked to record what they eat during a specific period. X-rays can determine bone density and reveal gastrointestinal disturbances, and heart and lung damage.

Not enough red blood cells in the blood.
Anorexia nervosa—
Eating disorder marked by malnutrition and weight loss commonly occurring in young women.
Pertaining to the study, prevention, or treatment of overweight.
A unit of heat measurement used in nutrition to measure the energy value of foods. A calorie is the amount of heat energy needed to raise the temperature of 1 kilogram of water 1°C.
Salts and minerals that ionize in body fluids. The major human electrolytes are sodium (Na+), potassium (K+), calcium (Ca 2+), magnesium (Mg2+), chloride (Cl-), phosphate (HPO4 2-), bicarbonate (HCO3-), and sulfate (SO4 2-). Electrolytes control the fluid balance of the body and are important in muscle contraction, energy generation, and almost all major biochemical reactions in the body.
Severe malnutrition in children primarily caused by a protein-poor diet, characterized by growth retardation.
Severe malnutrition in children caused by a diet lacking in calories as well as protein. Marasmus may also be caused by disease and parasitic infection.
Essential dietary elements that are needed only in very small quantities. Micronutrients are also known as trace elements. They include copper, zinc, selenium, iodine, magnesium, iron, cobalt, and chromium.
An organism that lives in or with another organism, called the host, in parasitism, a type of association characterized by the parasite obtaining benefits from the host, such as food, and the host being injured as a result.

Blood and urine tests are used to measure the patient's levels of vitamins, minerals, and waste products. Nutritional status can also be determined by:


Normalizing nutritional status starts with a nutritional assessment. This process enables a clinical nutritionist or registered dietitian to confirm the presence of malnutrition, assess the effects of the disorder, and formulate diets that will restore adequate nutrition.

Patients who cannot or will not eat, or who are unable to absorb nutrients taken by mouth, may be fed intravenously (parenteral nutrition) or through a tube inserted into the gastrointestinal (GI) tract (enteral nutrition).

Tube feeding is often used to provide nutrients to patients who have suffered burns or who have inflammatory bowel disease. This procedure involves inserting a thin tube through the nose and carefully guiding it along the throat until it reaches the stomach or small intestine. If long-term tube feeding is necessary, the tube may be placed directly into the stomach or small intestine through an incision in the abdomen.

Tube feeding cannot always deliver adequate nutrients to patients who:

Intravenous feeding can supply some or all of the nutrients these patients need.


Up to 10% of a person's body weight can be lost without adverse side effects; if more than 40% is lost, the situation is almost always fatal. Death usually results from heart failure, electrolyte imbalance, or low body temperature. Patients who are semiconscious or who have persistent diarrhea, jaundice, or low blood sodium levels have a poorer prognosis.

Some children with protein-energy malnutrition recover completely. Others have many health problems throughout life, including intellectual disability and the inability to absorb nutrients through the intestinal tract. Prognosis for all patients with malnutrition is dependent on the age of the patient and the length and severity of the malnutrition, with young children and the elderly having the highest rate of long-term complications and death.



Breastfeeding a baby for at least six months to one year is considered the best way to prevent early childhood malnutrition. The U.S. Department of Agriculture and Health and Human Service recommend that all Americans over the age of two:

Every patient admitted to a hospital should be screened for the presence of illnesses and conditions that could lead to protein-energy malnutrition. Patients with higher-than-average risk for malnutrition should be more closely assessed and reevaluated often during long-term hospitalization or nursing-home care.

See also Adolescent nutrition ; Anorexia nervosa ; Breastfeeding ; Calorie restriction ; Calories ; Cancer ; Childhood nutrition ; Eating disorders ; Intermittent fasting ; Liquid diets ; Obesity .



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Vesler, Lyman W., ed. Malnutrition in the 21st Century. New York: Nova Science, 2007.


Dewey, K. G., and M. Arimond. “Lipid-Based Nutrient Supplements: How Can They Combat Child Malnutrition?” PLoS [Public Library of Science] One 9, no. 9 (2012): e1001314.

Uauy, Richard, et al. “Global Efforts to Address Severe Acute Malnutrition.” Journal of Pediatric Gastroenterology & Nutrition 55, no. 5 (November 2012): 476–81.


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Academy of Nutrition and Dietetics, 120 South Riverside Plz., Ste. 2000, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600,, .

American Society for Nutrition, 9650 Rockville Pike, Bethesda, MD, 20814, (301) 634-7050, Fax: (301) 634-7894, .

British Nutrition Foundation, High Holborn House, 52-54 High Holborn, London, UK, WC1V 6RQ, +44 20 7404 6504, Fax: +44 20 7404 6747,, .

Doctors Without Borders, 333 7th Ave., 2nd Fl., New York, NY, 10001-5004, (212) 679-6800, Fax: (212) 679-7016, .

World Health Organization, Avenue Appia 20, 1211 Geneva 27, Switzerland, +41 22 791-2111, Fax: +41 22 791-3111,, .

Mary K. Fyke
Revised by Tish Davidson, AM

  This information is not a tool for self-diagnosis or a substitute for professional care.