Malnutrition: What you need to know

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

Causes of malnutrition include inappropriate dietary choices, a low income, difficulty obtaining food, and various physical and mental health conditions.

Undernutrition is one type of malnutrition. It occurs when the body does not get enough food. It can lead to delayed growth, low weight, or 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 have a severe impact on their health. In some cases, this can become life-threatening.

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

What is malnutrition?

Malnutrition occurs when a person gets too much or too little of certain nutrients.

Undernutrition occurs when they lack nutrients because they eat too little food overall.

A person with undernutrition may lack vitamins, minerals, and other essential substances that their body needs to function.

Malnutrition can lead to:

  • short- and long-term health problems
  • slow recovery from wounds and illnesses
  • a higher risk of infection
  • difficulty focusing at work or school

Some deficiencies can trigger specific health problems. For example:

A lack of vitamin A

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

A lack of vitamin C

A lack of vitamin C can result in scurvy. Scurvy is rare in the United States, but it can develop if a person does not have a varied diet with plenty of fresh fruits and vegetables.

Older adults, young children, those who consume a lot of alcohol, and some people with certain mental health conditions may be particularly at risk.

An overall deficiency

Lacking all nutrients can lead to kwashiorkor, which is a “severe form of malnutrition.” One symptom of this condition is a distended abdomen.

Marasmus is another potential result of severe nutritional deficiency. A person with marasmus will have very little muscle or fat on their body.


Some signs and symptoms of malnutrition include:

Eventually, a person may also experience difficulty breathing and heart failure.

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.

Anorexia nervosa is a mental health condition that can lead to severe malnutrition.


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

A 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.
  • Due to nausea, for example, taking medications that make eating difficult makes sense.

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

Mental health conditions

Undernutrition or malnutrition can affect people with:

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 reach 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:

  • Crohn’s disease
  • Ulcerative colitis
  • Celiac dise ase
  • Persistent diarrhea, vomiting, or both

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, and 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 healthy food to supply the body with essential nutrients.

Risk factors

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

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

  • Especially when they are in the hospital or long-term institutional care,
  • For example, people who are socially isolated 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 or anorexia nervosa

Some people may need to take supplements if they follow a specific diet. Which supplements are good for a person following a vegan diet? 


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

If a doctor suspects Crohn’s disease, celiac disease, or another condition, they may carry out laboratory tests to confirm a diagnosis. Treating these conditions can improve a person’s nutritional status.

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

The five steps are as follows:

Step 1: Measure a person’s height and weight, calculate their body mass index (BMI), and provide a score.

Step 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 2.

Step 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, the score will be 3.

Step 4: Add the scores from steps 1, 2, and 3 to obtain an overall risk score.

Step 5: Use local guidelines to develop a care plan based on the score.

The score will be one of the following:

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

Doctors must 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.


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

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 person may need to:

  • spend time in the hospital
  • gradually start taking in nutrients over a number of days
  • receive nutrients such as potassium and calcium intravenously

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


To prevent malnutrition, people need to consume a range of nutrients from a variety of food types. Older adults, young children, people with severe or chronic illness, and others may need additional care to ensure that they 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.

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