Malnutrition is a broad topic but simply indicates inadequate nourishment to maintain health and normal development. The term may reflect insufficient calories, protein, vitamins, or minerals or to an overabundance of any of these elements that leads to medical conditions such as obesity. In this article, the focus will be on insufficient nutrition as obesity will be discussed elsewhere.

Causes of Malnutrition

People generally assume that malnutrition occurs only in underdeveloped countries in which there is not enough food or only in the poor, but that is not the case. On the contrary, malnutrition can also occur in the United States and other developed nations and in people from all walks of life. A lack of nutrition can result from a variety of causes, including diseases that lead to the inability to absorb nutrients, a decreased appetite and oral intake, and increased caloric need. In these situations, the duration of malnutrition can be quite brief, as with an acute viral gastroenteritis (stomach flu) with vomiting and diarrhea, or can be very prolonged as with cancer or severe trauma. Malnutrition is also common in the elderly. Older people experience malnutrition for a variety of reasons. The condition can be experienced because of medical illnesses but also due to social isolation and limitations in mobility and resources. Anorexia (along with other eating disorders) is another significant cause of malnutrition. These disorders are often most difficult to treat as well. See the table for causes of malnutrition.

Signs and Symptoms

The body has the remarkable ability to adjust to nutritional limitations by decreasing metabolism and energy requirements. As the malnutrition continues, however, the body is not able to maintain all its usual functions. Weight loss is generally the first sign of malnutrition and when there is loss of 10% of body weight, a diagnosis of malnutrition can be made. Poor nutrition will eventually affect every organ in the body: the heart becomes weaker, the immune system is less able to protect against infection, and even the intestines are less able to absorb the nutrients that are ingested. In children, these changes can result in slowed growth and development, total body swelling, low blood pressure, and slow heart rate. Dehydration and electrolyte abnormalities can lead to erratic heart rhythms, which can be fatal. Most people can recover even after severe and prolonged starvation, but when weight loss exceeds 40% of ideal body weight, death almost always results.


The diagnosis of malnutrition is as diverse as the types of nutritional deficits. The first sign of protein and calorie malnutrition is weight loss. This condition can be confirmed by findings of low levels of certain proteins in the blood, mild anemia, decreased numbers of certain white blood cells (lymphocytes), and decreased reaction to infections. These changes do not have to be present for malnutrition to exist, but their presence indicates a poorer prognosis. The most important tool for diagnosis of malnutrition is a high index of suspicion. People who do not look for nutritional problems probably won’t find any problems. One must be suspicious of malnutrition in anyone who is losing weight, has increasing fatigue, or shows any of the abnormalities listed above.

Treatment of Malnutrition

Treatment for malnutrition needs to be directed at the cause of the condition. In severe cases of malnutrition, the first step is to insure adequate fluid and electrolyte (mineral salt) intake and correct other medical complications such as infections. Most malnourished people are severely dehydrated and have electrolyte abnormalities, such as low levels of potassium, calcium, phosphate, and magnesium. These imbalances can lead to irregular heart rhythms, which can be fatal, so it is essential that the imbalances be corrected before any other steps are taken. The next step is to replenish calories. This must be done slowly and carefully. In the severely malnourished, rapid replacement of protein and calories can lead to "re-feeding syndrome," which refers to very low levels of phosphate and can be life threatening. There are guidelines specifying how many calories and grams of protein can be given in a day to re-feed a malnourished person safely.

The actual mode of re-feeding is a rather broad topic and will be covered briefly. In people who are alert and have a functioning intestinal tract, food can be eaten normally. If the intestinal tract is working, but one is not alert, a feeding tube placed into the stomach can be used to provide nutrients. The other option is giving all nutrients intravenously. This is the least preferred method and should be reserved for those with a non-functioning digestive tract.

Another important aspect of treatment is physical therapy to help the person regain strength. Muscle wasting is a key feature of malnutrition. The lost muscle mass needs special attention to restore itself to functional levels. This is true for all types of malnutrition, from the elderly with medical problems to the young starvation victim.


The prognosis for malnutrition is variable based on the cause. In patients who have medical illnesses leading to malnutrition, the outcome in terms of nutrition depends on the outcome of the illness. For example, in a patient with cancer that causes nausea and decreased appetite, the patient’s nutrition is not going to improve unless the nausea and appetite improve. Likewise, an anorexic will continue to have poor nutrition unless the underlying eating disorder can be controlled. If the cause of malnutrition is correctable and is caught early enough, the prognosis is very good.

Table 1: Causes of malnutrition
Decreased intake Increased nutrient loss Increased Need/Metabolism
Poor appetite Inability to absorb nutrients Fever
Nausea and vomiting Diarrhea Infection
Difficulty swallowing Bleeding Cancer
Pain Diabetes Surgery
Intestinal blockage Protein loss from kidney Trauma
Poor teeth or intestinal disease Burns
Starvation (intentional or poverty)
Social isolation
Drug or alcohol abuse

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