Malnutrition is when a person’s diet does not provide enough nutrients or the right balance of nutrients for optimal health.

Causes of malnutrition include:

  • unsuitable dietary choices
  • having a low income
  • difficulty obtaining food
  • various physical and mental health conditions

Undernutrition is one type of malnutrition. It occurs when the body does not get enough food and enough necessary nutrients. It can lead to:

  • delayed growth
  • low weight
  • wasting

If a person does not get the right balance of nutrients, they can also have malnutrition. It is possible to have obesity with malnutrition.

When a person has too little food, a limited diet, or a condition that stops their body from obtaining the right balance of nutrients, it can severely impact their health. In some cases, this can become life threatening.

This article looks at malnutrition in detail, including the causes, symptoms, and treatments.

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Malnutrition is an imbalance in dietary intake. It occurs when a person has too much or too little food or essential nutrients. A person with malnutrition may lack vitamins, minerals, and other essential substances that their body needs to function.

People may become malnourished if they do not eat enough food overall. However, people who eat plenty but do not have enough variation in their diet can also become malnourished.

Malnutrition can lead to:

  • short- and long-term health problems
  • slow recovery from wounds and illnesses
  • a higher risk of infection

Some deficiencies can trigger specific health problems. For example:

Lack of vitamin A

Around the world, many children develop vision problems due to a lack of vitamin A.

Lack of vitamin C

A lack of vitamin C can result in scurvy.

Scurvy is rare in the United States (U.S.), but it can develop if a person does not have a varied diet with plenty of fruits and vegetables. Fresh, frozen, and canned fruits and vegetables all contain vitamin C.

People who are particularly at risk of scurvy include:

  • older adults
  • young children
  • those who consume a lot of alcohol
  • some people with certain mental health conditions

An overall deficiency

Malnutrition can lead to marasmus, which is a severe form of malnutrition. Marasmus is a deficiency of protein and overall energy intake.

A person with marasmus will have very little muscle or fat on their body.

Overnutrition

Overnutrition is another type of malnutrition. It occurs when a person takes in more nutrients than they need. The result may be an accumulation of body fat from the excess nutrients, resulting in overweight or obesity.

Overnutrition has several health implications. People who have overweight or obesity are at greater risk of:

The rate of overnutrition is growing worldwide. The World Health Organization (WHO) reports that in 2020, 5.7% of children under 5 were overweight, an increase from 5.4% in 2000.

In addition, the number of adults with obesity almost tripled worldwide from 1975 to 2016.

Some signs and symptoms of malnutrition include:

  • weight loss
  • a lack of appetite or interest in food or drink
  • tiredness and irritability
  • an inability to concentrate
  • always feeling cold
  • depression
  • loss of fat, muscle mass, and body tissue
  • a higher risk of getting sick and taking longer to heal
  • longer healing time for wounds

Eventually, a person may also experience heart failure.

Symptoms in adults vs. children

Children may present with different malnutrition symptoms than adults.

In children, there may be:

  • a lack of growth and low body weight
  • tiredness and a lack of energy
  • irritability and anxiety
  • slow behavioral and intellectual development, possibly resulting in learning difficulties

Treatment is possible. In some cases, however, malnutrition can have long-term effects.

Malnutrition can occur for various reasons. The sections below outline these potential causes in more detail.

Low intake of food

Some people develop malnutrition because there is not enough food available, or because they have difficulty eating or absorbing nutrients.

This can happen as a result of:

  • cancer
  • liver disease
  • conditions that cause nausea or make it difficult to eat or swallow
  • taking medications that make eating difficult — due to nausea, for example

Mouth problems such as poorly fitting dentures may also contribute to malnutrition.

Mental health conditions

Undernutrition or malnutrition can affect people with:

Eating disorders can severely affect the quality of life of people living with these conditions and those close to them. Early intervention and treatment greatly improve the likelihood of recovery.

Anyone who suspects that they or a loved one has an eating disorder can contact the National Eating Disorder Association for advice and support via:

  • phone or text at 800-931-2237
  • online chat, by going to this link

These services are only open during specific hours. Someone in crisis can text “NEDA” to 741741 at any time to get support from a trained volunteer at Crisis Text Line.

Alternatively, the Substance Abuse and Mental Health Services Administration (SAMHSA) run a Disaster Distress Helpline that people can contact on 800-985-5990 for 24-7 support.

Many other resources are available, including:

Social and mobility problems

Factors that can affect a person’s eating habits and potentially lead to malnutrition include:

  • being unable to leave the house or go to a store to buy food
  • finding it physically difficult to prepare meals
  • living alone, which can affect a person’s motivation to cook and eat
  • having limited cooking skills
  • not having enough money to spend on food

Digestive disorders and stomach conditions

If the body does not absorb nutrients efficiently, even a healthful diet may not prevent malnutrition.

Examples of digestive and stomach conditions that may cause this include:

Alcohol use disorder

Consuming a lot of alcohol can lead to gastritis or long-term damage to the pancreas. These issues can make it hard to:

  • digest food
  • absorb vitamins
  • produce hormones that regulate metabolism

Alcohol also contains calories, so a person may not feel hungry after drinking it. They may, therefore, not eat enough healthful food to supply the body with essential nutrients.

In some parts of the world, widespread and long-term malnutrition can result from a lack of food.

In wealthier nations, however, those most at risk of malnutrition include:

  • older adults, especially when they are in the hospital or in long-term institutional care
  • people who are socially isolated — for example, due to mobility issues, health problems, or other factors
  • people with a low income
  • people recovering from or living with a serious illness or condition
  • those who have difficulty absorbing nutrients
  • people with chronic eating disorders, such as bulimia nervosa or anorexia nervosa

A few key signs of malnutrition indicate that it is time for a person to seek care from a doctor. These signs include:

  • unexplained, unintentional weight loss of more than 5% in the last 3–6 months
  • presence of other malnutrition symptoms
  • a worry that someone else may be showing signs of malnourishment
  • if a person experiences signs of an eating disorder, or sees these in someone else

Likewise, a person should encourage a loved one to see a doctor if they show signs of malnourishment. Some people may not recognize the symptoms in themselves, while loved ones sometimes can.

If a person shows or notices any symptoms or signs of malnutrition, the first step is to find out why.

If a doctor suspects Crohn’s disease, celiac disease, or another condition, they may evaluate the patient’s condition by:

  • asking about medical history
  • conducting a physical exam
  • ordering testing

Treating underlying conditions can improve a person’s nutritional status.

A healthcare professional may also carry out the following:

  • blood tests for general screening and monitoring
  • tests for specific nutrients, such as iron or vitamins
  • prealbumin tests, as malnutrition commonly affects levels of this protein
  • albumin tests, which may indicate liver or kidney disease

A tool to identify risk

Some tools can help identify people who have or are at risk of malnutrition.

One way to assess adults is by using the Malnutrition Universal Screening Tool (MUST). 2018 research has shown this to be a reliable tool.

Experts designed this tool to identify adults, especially older adults, with malnourishment or a high risk of malnutrition. It is a five-step plan to help healthcare professionals diagnose and treat these conditions.

The five steps are as follows:

  1. Measure a person’s height and weight, calculate their body mass index (BMI), and provide a score.
  2. Note the percentage of unplanned weight loss and provide a score. For example, an unplanned loss of 5–10% would give a score of 1, while a 10% loss would score a 2.
  3. Identify any mental or physical health conditions and provide a score. For example, if a person has been acutely ill and taken no food for over 5 days, this would lead to an additional 2 points.
  4. Add the scores from steps 1, 2, and 3 to obtain an overall risk score.
  5. Use local guidelines to develop a care plan based on the score.

The score will be one of the following:

  • low risk: 0
  • medium risk: 1
  • high risk: 2 or more

Doctors only use MUST to identify overall malnutrition or the risk of malnutrition in adults. The test will not identify specific nutritional imbalances or deficiencies.

Nutritional deficiency anemia can result if a person’s diet cannot provide the nutrients they need. Learn more about it here.

If a doctor diagnoses malnutrition, they will make a treatment plan for the person. The person may also need to meet with a dietician and other healthcare professionals.

Treatment will depend on the severity of the malnutrition and the presence of any other underlying conditions or complications.

It may include:

  • ongoing screening and monitoring
  • making a dietary plan, which might include taking supplements
  • treating specific symptoms, such as nausea
  • treating any infections that may be present
  • checking for any mouth or swallowing problems
  • suggesting alternative eating utensils

In severe cases, a doctor may administer nutrients intravenously (through an IV).

The person’s healthcare team will continue to monitor them to ensure they get the nutrition they need.

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

Older adults, young children, people with severe or chronic illness, and others may need additional care to obtain the nutrients they need.

Anyone who starts to show signs of malnutrition or undernutrition should see a doctor for a diagnosis and treatment.

In the U.S., effective treatment is usually available, although the outlook and time needed for recovery will depend on the cause of the malnutrition.

Malnutrition is the result of an improper diet. It can result from too few nutrients (undernutrition) or too many nutrients (overnutrition).

People who experience undernutrition often have:

  • low weight
  • difficulty recovering from injuries
  • lack of appetite
  • fatigue
  • depression
  • among other symptoms

But malnutrition is not the result of poor diet choices in every case. Sometimes, malnutrition occurs because a person:

  • does not have easy access to food
  • cannot leave their home to buy food
  • cannot cook meals
  • has a digestive disorder that prevents their body from properly absorbing nutrients

Helping patients treat malnutrition is an important goal for many healthcare professionals. Together, a doctor and patient can review possible causes of malnutrition and help develop more nutrient-dense eating plans.