What is malnutrition

Malnutrition is a physiological state of the organism characterised by the insufficient assumption or malabsorption of one or more nutrients that are required and normally present in a varied and balanced diet.

The most common form of malnutrition is protein–energy malnutrition. This condition sets in rapidly in the case of acute or chronic illness, and slowly over a period of months if associated with a reduced/incorrect intake of nutrients.

The World Health Organisation (WHO) defines malnutrition as “a cellular imbalance between the supply of nutrients and energy and the demands of the body to guarantee growth, survival, bodily functions and reproduction”.


Classification of malnutrition on the basis of percentage of body weight loss:

  • Mild: weight loss (of standard weight) 5-10%
  • Moderate: weight loss (of standard weight) 11-20%
  • Severe: weight loss (of standard weight) > 20%

Causes of malnutrition

Protein–energy malnutrition is caused by a lack of nutrients in a diet. This lack can be due to physical factors such as old age, disability, prolonged confinement to bed, alteration in taste or smell; medical conditions that may lead to a loss of appetite (e.g. tumours), an alteration to cognitive conditions (e.g. neurodegenerative illnesses), frequent hospitalisation or eating disorders which further interfere with proper nutrition.

Among the possible causes of malnutrition, dysphagia plays an important role, as the patient has difficulty in swallowing and therefore consumes less.

What categories are at risk

Malnutrition is a particular risk for:

  • the elderly, either in nursing homes or hospital, and above all those suffering from chronic metabolic diseases
  • patients with neurological conditions
  • pregnant women
  • individuals at risk of systemic infections

Malnutrition can affect people of all ages. Protein–energy malnutrition is typical in the elderly and on average affects 5-12% of elderly people who live at home, 26-65% pf elderly people in hospital, and 60-70% of those institutionalised.

Symptoms of malnutrition

The most common symptom of malnutrition is significant weight loss. People who have lost more than 10% of their body weight over a period of three months can be considered at risk of malnutrition.

The most common physical symptoms of protein–energy malnutrition:

  • a reduction of subcutaneous tissue, muscle mass and body tissue, which can be seen most often in the legs, arms, buttocks and face
  • oedemas
  • neurological problems and anomalies
  • changes in the oral cavity (mouth, lips and gums inflamed and usually swollen)
  • muscular cramping and pain
  • alterations of the skin (dry and flaking, fragile, swollen, pale, loss of elasticity and poor healing)
  • alternations in hair condition (dry and faded)
  • tiredness and lack of appetite
  • increased frequency of illness and difficulty in recovering from the same
  • appearance of pressure sores
  • BMI lower than 18.5

The main consequences of malnutrition

Complications due to protein–energy malnutrition can be many, including the following:

  • Hypothermia
  • Hypoglycaemia
  • Encephalopathy
  • Diarrhoea
  • Cardiac arrhythmia
  • Infections
  • Decreased quality of life
  • Depression and apathy
  • Increased risk of fracture

How to diagnose malnutrition

Screening is a process that identifies people at risk of or suffering from malnutrition that require a higher level of assessment. It can be carried out with the use of tests, such as Mini Nutritional Assessment (MNA), an easy and immediate tool that is specifically for the elderly. A positive result from the screening shows that the subject will have to undergo nutritional evaluation in order to assess the presence of protein–energy malnutrition and indicate the severity.

Nutritional assessment includes:

  • Pathological, pharmacological and nutritional case history
  • Objective examination
  • Measuring of anthropometric parameters (weight and height) in order to define the BMI (body mass index Kg/m²)
  • Laboratory tests

How to prevent and treat malnutrition

It is particularly important to select food of high nutritional value and make small changes in diet in order to qualitatively improve the assumption of food and more easily tackle the risk of malnutrition associated with old age and illness.

Treatment for malnutrition takes the form of specific nutritional therapy, in order to increase the level of calories and proteins introduced with food.

In the event that natural nourishment is not sufficient, it is necessary to contact one’s nutritionist, who will be able to recommend the most suitable treatment, with high-calorie and high-protein oral nutritional supplements.


KATSILAMBROS, Nikolaos, et al. (ed.). Clinical nutrition in practice. John Wiley & Sons, 2011
Kaiser MJ, Bauer JM, RJM, R C, Uter W, Guigoz Y, Cederholm T et al. Frequency of malnutrition in older adults: a multinational perspective using the mini nutritional assessment. J Am Geriatr Soc. 2010 Sep;58(9):1734-8.
CEDERHOLM, Tommy, et al. Diagnostic criteria for malnutrition–an ESPEN consensus statement. Clinical nutrition, 2015, 34.3: 335-340.