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Common signs of undernutrition

Claire Sulmont-Rossé & Isabelle Maître describe the warning signs that indicate undernutrition as well its effects and how to reverse it.

Undernutrition: a silent disease

Undernutrition is a recognised pathology of older adults. In the older population, it’s caused by insufficient food intake and/or compromised use of nutrients by the body such as reduced absorption in the digestive tract. Too often ignored, undernutrition is associated with numerous serious health consequences.

What are the causes and consequences of undernutrition?

Undernutrition is caused by an imbalance between the nutritional needs of the human body and the supply. In other words, not enough nutrients are eaten for the body’s requirements. The body therefore draws on its internal reserves to compensate, taking protein from muscles or calcium from bones, for example. The imbalance leads to loss of muscle mass, impairment of immune function, increased risk of falls and fractures, as well as infections and hospital admissions1. Undernutrition threatens the health, autonomy and life expectancy of older adults. It worsens existing diseases (by causing complications and longer convalescence) and the resulting muscle loss leads to dependence on others for everyday life activities. In older people suffering from undernutrition, the risk of mortality is multiplied by four2.

The downward spiral of undernutrition. Original © Carolab, redrawn by University of Reading

Who is affected by undernutrition?

Several studies have shown that undernutrition affects 1 in 10 older people living independently at home. However, it affects 5 in 10 older people living in nursing homes, and 7 in 10 older people in hospital3. Being overweight, even obese, does not protect against undernutrition. A study in France showed that around a quarter of overweight or obese older people are also undernourished4. And when older adults lose weight, they lose muscle mass, whatever their starting weight.

Prevention and treatment

To prevent and treat undernutrition, it’s essential to:

  • Be informed about the nutritional needs of older adults
  • Provide a suitable diet, both in term of quality (variety) and quantity of nutrients
  • Monitor weight, particularly in high-risk situations.

Monitor weight: Weight loss in older adults is never trivial. Clothing that’s too loose, a belt that’s too tight or a watchstrap that floats are all warning signs, but nothing beats regular weighing. It’s the most effective way of detecting undernutrition and enables you to react quickly. Regular weighing means once a month, or more often in high-risk situations (once a week during hospitalisation). When in doubt, inform your doctor.

There are many nutrition screening tools in use across the world. However, the most commonly used screening tool in all care settings in the UK is the Malnutrition Universal Screening Tool (MUST). This was developed and launched by BAPEN in 2003. It was designed to be valid, reliable and easy to use in all adults. It can detect over-nutrition as well as under-nutrition and is linked to a flexible care plan. (It is not designed to detect deficiencies in or excessive intakes of vitamins and minerals.)

Identify high-risk situations: There are many situations in an older adult’s life that can lead to a loss of appetite and undernutrition. Some high-risk situations are obvious (such as hospitalisation and injury), but others are more discreet, or even downplayed by the person concerned. If you notice someone you care for has started to regularly say things like, “Oh, I don’t want very much today, I’m not hungry”, “I’m not hungry, it’s natural, I’m getting older”, or “I’d rather just have a biscuit to be honest,” then these could be warning signs. All older people can be affected by undernutrition at some point in their lives, and those around them need to be extra vigilant at such times.

Undernutrition: some warning signs. © Renessens.

Undernutrition is not inevitable. If detected and treated in time, the situation can be reversed. Paying attention to the appetite and weight of older people is therefore essential to enable them to age well. If you are worried about yourself or someone you care for then please contact your doctor or ask to have a chat with your community dietician.


Take a look at the MUST calculator which allows you to establish a malnutrition category based on objective criteria (height, weight and BMI) but also on subjective criteria if for any reason, objective measurements are difficult to take. Do you use this tool in your care setting? If so, please share your experiences. If not, how do you think it might benefit the adult(s) in your care?


  1. Landi F, et al. Anorexia of Aging: Risk Factors, Consequences, and Potential Treatments. Nutrients. 8(2):69. 2016.
  2. Sanchez-Rodriguez D, et al. Mortality in malnourished older adults diagnosed by ESPEN and GLIM criteria in the SarcoPhAge study. J Cachexia Sarcopenia Muscle 11(5):1200-1211. 2020.
  3. Stratégie de prise en charge en cas de dénutrition protéino-énergétique chez la personne âgée . Haute Autorité de santé. 2007.
  4. Sulmont-Rossé C, Van Wymelbeke-Delannoy V, Maître I. Prevalence of Undernutrition and Risk of Undernutrition in Overweight and Obese Older People. Front Nutr. 9:892675. 2022.
© University of Reading, INRAE, CHU, NOFIMA, VUB
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Ageing Well: Nutrition and Exercise for Older Adults

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