What Is Malnutrition?


Malnutrition is a serious condition that develops when there's an imbalance in the nutrient intake that our body requires to maintain healthy function. Malnutrition can be considered either undernutrition or overnutrition.

Generally, our body requires a variety of essential nutrients in specific amounts to maintain its bodily functions. Malnutrition occurs when our diet does not contain enough of these nutrients. A person can be malnourished from an overall deprivation of nutrients or even if they are lacking some types of minerals in their diet. A lack of a few nutrients or having excessive amounts of them in the diet can both impose serious health consequences.

Understanding malnutrition and maintaining a healthy and balanced diet is critical to preventing the condition and the risks of developing health conditions.

Causes of malnutrition

Malnutrition can happen for a variety of reasons. Moreover, it particularly varies depending on which form of malnutrition a person has. Undernourishment is usually caused by a lack of the right amounts of essential minerals and vitamins in the diet. Certain medical conditions can also cause malnutrition by preventing nutrient absorption in the body. 

The following are some common causes of under nutrition:

  • Restricted access to healthy foods
  • Having limited financial resources
  • Difficulty eating food because of certain reasons such as nausea, poor fitting of dentures, or swallowing issues (dysphagia)
  • Medical conditions that  causes depletion of calories, like chronic diarrhoea, vomiting, or cancer
  • Conditions like pregnancy or breastfeeding where extra need for calories is required
  • Mental health problems, including depression, dementia, and schizophrenia, can affect people with malnutrition1
  • Having eating disorders like anorexia nervosa or bulimia
  • Digestive disorders may cause malnutrition due to the inability to absorb food content efficiently. This may include Ulcerative colitis,  celiac disease, Crohn's disease, or pancreatic insufficiency

On the other hand, overnutrition is caused when a person consumes excessive nutrients in their diet. Some of the common causes of overnutrition may include:

  • Sedentary lifestyle
  • Binge eating
  • Consuming less nutritious foods
  • Hormonal imbalance, which may interfere with the sense of satiety
  • Medical conditions that can slow metabolism (for example, hypothyroidism)
  • Excessive usage of dietary supplements
  • Having chronic stress, anxiety, or depression

Signs and symptoms of malnutrition

The signs and symptoms of undernutrition may include:

  • Weakness
  • Fatigue
  • Low body weight
  • Stunted growth in children
  • Changes in skin coloration
  • Tender bones and depleted muscles or fat
  • The weakened immune system, - prone to frequent infections
  • Prominent hair loss
  • Brittle and dry skin
  • Bleeding gums
  • Low body temperature
  • Changes in mood such as anxiety and stress
  • Increased sensitivity to light exposure
  • Susceptible to bruising and rashes
  • Low energy levels
  • Slow wound healing process

For overnutrition, the sign and symptoms may look like:

  • Heart disease
  • Weight gain
  • Insulin resistance
  • Frequent urge to urinate
  • Heart rate irregularities
  • Blood pressure
  • Anxiety

Management and treatment for malnutrition

If someone is undernourished, improving nutritional intake consisting of healthy and high-calorie-based supplements could help to restore the missing needs of the body. Including nutrient-dense foods and beverages that contain proteins, vitamins, minerals, and fibre in the diet can help to manage malnutrition.

Whereas, if someone is diagnosed with severe under nutrition, the recovery may take several weeks to become accompanied by the refeeding procedure. When a person's body is deprived of nutrients, it alters in various ways to adapt to undernutrition. The refeeding process reintroduces the calorie intake so the body can recover and go back to its old way of working.

Refeeding can impose complications if it's implied too quickly. It is best to start the refeeding process under proper medical observation in the first few weeks to avoid and manage complications like refeeding syndrome.

In instances of overnutrition, it is typically managed with weight loss, diet, and lifestyle changes. Weight loss management can help reduce the risks of developing secondary health problems, including heart disease and diabetes. Moreover, overnutrition can also be treated by pairing weight loss with diet plans, medicines, certain medical procedures, counselling (behavioural therapy), and educational sessions on nutrition to provide long-term support in changing the lifestyle. 

Health practitioners may also evaluate if you have any underlying medical conditions, such as mental health disorders or thyroid diseases, to treat overnutrition.


How is malnutrition diagnosed? 

Malnutrition comes into consideration when an individual exhibits or observes any signs of it. To diagnose malnutrition, doctors may conduct a physical examination along with a medical history and dietary intake to check the extent of the problem. They may also order some laboratory tests to specify if there's any nutrient deficiency. These tests for general monitoring may include:

  • Tests for evaluating nutrients like iron or vitamins
  • Checking prealbumin levels, this type of protein is commonly affected in malnutrition
  • Albumin test to check if there are any underlying liver or kidney diseases

Furthermore, health providers may use some tools to identify individuals who have or are at risk of developing malnutrition. One way to assess is by using a reliable tool known as the Malnutrition Universal Screening Test (MUST), which is designed to pinpoint people, especially older adults, who are at high risk of malnutrition.

MUST is a five-step plan that calculates an overall score by measuring a person's body mass index (BMI), and percentage of unplanned weight loss, evaluating any mental or physical health issues, and obtaining scores to develop an extensive care plan to treat the condition.

In general, doctors use the MUST tool to only identify the risk of malnutrition in adults. It does not specify any nutritional deficiencies or imbalances in the body.

How can I prevent malnutrition? 

Malnutrition is a serious global health issue. Lack of nutritional knowledge and poverty are two of the leading causes in both developing and developed countries. The best way to prevent malnutrition is to eat a healthy, well-balanced diet consisting of essential nutrients. If you have enough sources of nutritious foods, you will be less likely to overeat.

What are the types of malnutrition? 

Malnutrition refers to an imbalance, which can happen due to a lack of dietary intake or overconsumption. It can also mean that it lacks the right proportion of both macronutrients (carbohydrates, fats, and proteins) and micronutrients (vitamins and minerals). Following are the types and subtypes of malnutrition:


Overnutrition simply happens when you consume more nutrients than you require daily. Though many people believe malnutrition only refers to a lack of nutrients, the World Health Organization (WHO) added overconsumption to the malnutrition definition to concede its detrimental effects on health. Overnutrition often leads to obesity, heart disease, diabetes, and certain types of cancer.

  • Energy overnutrition: This occurs when you consume large amounts of calories, which may gradually result in obesity unless physical exercises are implemented. This consumption can also be considered macronutrient overnutrition. When we consume extra calories, the body stores them as fat when it does not need to use them
  • Micronutrient overnutrition: This type of malnutrition happens when you overconsume a certain nutrient. Although rare, it typically occurs because of megadoses of any nutrient supplement, which can create toxic effects such as acute poisoning


This refers to when you don't consume enough nutrients in your daily diet, or you might have a medical condition that interferes with nutrient absorption. Like overnutrition, undernutrition also consists of two subtypes

  • Protein-energy malnutrition (PEM): This is also known as "energy undernutrition," which is a particularly commonly linked deficiency of macronutrients. This type is generally found in underdeveloped countries where people don't get enough access to healthy food sources. PEM can happen in children who are undernourished and underweight. People with protein-energy malnutrition can suffer from starvation (or marasmus) due to a severe lack of energy that may result in poor growth or even death. Moreover, another form of PEM is protein deficiency, which is a condition called kwashiorkor. The most prominent features of kwashiorkor are thin arms and legs with a bloated abdomen. Despite the information, the exact underlying mechanism is still not fully understood2
  • Micronutrient undernutrition: In this type of malnutrition, a person is deficient in one or more essential nutrients. In some cases, chronic health problems cause malabsorption, leading to micronutrient undernutrition

Malnutrition can be acute or chronic. Acute malnutrition results from inadequate energy intake caused by social, economic, environmental, or health-related factors.3 However, chronic malnutrition occurs because of prolonged episodes of poor nutrition.

Who are at risk of malnutrition? 

Malnutrition can affect anyone, though it is likely more common in people who:

  • are socially isolated, due to health or mobility problems
  • are recovering or diagnosed with serious illness
  • are poor or have low income
  • have eating disorders like anorexia or bulimia nervosa
  • elderly people as ageing causes a decline in several physiological functions4
  • children, because they require great nutritional needs for their healthy development. According to the World Health Organization, children, infants, adolescents, and even women are at greater risk of developing malnutrition5

How common is malnutrition? 

Malnutrition is fairly common around the world. In the UK, it is nearly estimated that around 3 million people at any one time are either living with malnutrition or are at risk of developing it because they do not consume enough nutrients.6

When should I see a doctor? 

It is advised to make an appointment with your healthcare provider if:

  • Unintentional or unexplained weight loss or gain over the past few months (3-6 months)
  • You notice symptoms of malnutrition such as weakness, fatigue, and apathy
  • Experiencing signs of an eating disorder, or if you observe these symptoms in someone else

If you notice any signs related to malnutrition in your close relatives, it is best to encourage them to visit a doctor. Some individuals often do not recognise if they are developing malnutrition symptoms; encouraging them to seek treatment may help improve their health.


Malnutrition is a major health condition that affects people around the globe. It typically develops when there's a lack of essential nutrients needed for healthy body function. Malnutrition can indicate serious health complications if a person is undernourished or consumes nutrients excessively (overnutrition). 

In both developed and underdeveloped countries malnutrition can affect people through different factors. Malnutrition is treatable and can be prevented by following a well-balanced diet, becoming aware of nutritional education, and undergoing medical procedures if advised by your healthcare professional.


  1. Saunders J, Smith T. Malnutrition: causes and consequences. Clin Med (Lond) [Internet]. 2010 Dec [cited 2023 Mar 23];10(6):624–7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4951875/
  2. Bhutta ZA, Berkley JA, Bandsma RHJ, Kerac M, Trehan I, Briend A. Severe childhood malnutrition. Nat Rev Dis Primers [Internet]. 2017 Sep 21 [cited 2023 Mar 23];3(1):1–18. Available from: https://www.nature.com/articles/nrdp201767
  3. Dipasquale V, Cucinotta U, Romano C. Acute malnutrition in children: pathophysiology, clinical effects and treatment. Nutrients [Internet]. 2020 Aug 12 [cited 2023 Mar 23];12(8):2413. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7469063/
  4. Norman K, Haß U, Pirlich M. Malnutrition in older adults—recent advances and remaining challenges. Nutrients [Internet]. 2021 Aug 12 [cited 2023 Mar 23];13(8):2764. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8399049/
  5. Malnutrition [Internet]. [cited 2023 Mar 23]. Available from: https://www.who.int/health-topics/malnutrition
  6. Malnutrition matters - british nutrition foundation [Internet]. [cited 2023 Mar 23]. Available from: https://www.nutrition.org.uk/life-stages/older-people/malnutrition-and-dehydration/malnutrition-matters/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Sadaf Ahmed

Master of Science - MSc, Physiology, Clinical & Molecular Hematology, Karachi University, Pakistan

Sadaf is an experienced writer who creates a quality and well-researched scripts particularly related to Health Sciences.

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