Ondergewicht en ondervoeding Engels

Underweight and malnutrition

When are you underweight

Underweight is when a person weighs less than is good for their health. Underweight is a risk indicator for malnutrition. Underweight is easily diagnosed with the Body Mass Index (BMI) and the measurement of waist circumference. A person is underweight if their BMI is below 18.5.

Other boundaries

Different limits are used for people over 65 and for COPD patients, namely a BMI of less than 20 for people over 65 and less than 21 for people with COPD. To determine malnutrition, a BMI limit of less than 20 is used for adults up to 70 years of age and a BMI limit of less than 22 for those 70 years of age and older, in combination with a nutrient deficiency or disease. Different cut-off values also apply to children. Children are growing and therefore height, weight and BMI depend on age.

How many people are underweight?

The CBS health survey 2019 shows that 2.5% of the Dutch population aged 4 years and older are underweight. CBS uses the BMI limit of 18.5 for all adults.

Causes of underweight

Underweight occurs when the amount of energy someone takes in through eating and drinking is less than the body uses (burns) over a long period of time. Underweight is relatively common among elderly people in care institutions and hospitals and among the sick. Underweight can be caused by, among others:

  • lack of appetite, e.g. due to loss of taste and smell, illness or lack of exercise
  • chewing and swallowing problems
  • a poorly functioning intestine. The intestine is then less able to absorb nutrients, for example due to an intestinal infection or intestinal disease
  • side effect of medicines
  • Fear, loneliness, sadness, depression.
  • an eating disorder
  • increased energy consumption, for example in the case of an infection or cancer

Consequences of being underweight

Being underweight entails health risks because there is a high risk of deficiencies in nutrients such as proteins, essential fatty acids, vitamins and minerals. The immune system deteriorates and a person may feel lethargic and tired. The body uses reserves from fat and muscle tissue. This causes fat and muscle tissue to be broken down. The breakdown of muscle tissue is particularly harmful. If the underweight condition is prolonged, the risk of bone fractures also increases.

Dietary advice for underweight

For someone who is underweight, it is wise to stop losing weight and try to gain some. If you have lost a lot of weight in a short time without an apparent reason, it is best to see your doctor. Also, if you suspect an eating disorder, always see your GP.

If you are unable to reach a healthy weight within a few months, it is wise to see your GP. The doctor will investigate the cause of the underweight and can refer you to a specialist and/or dietician if necessary.

Are you underweight? Then your health insurance will reimburse you for a number of hours with a dietician.

Healthy eating

For people who are underweight, healthy eating is important. In this way, they get all the nutrients that the body needs, such as proteins, essential fatty acids, vitamins and minerals. The emphasis is on food with sufficient protein and energy, combined with exercise for muscle building.

Gaining weight in a healthy way

For people who are underweight, it is to gain weight.


Malnutrition occurs when a person’s intake of energy or nutrients is less than what is needed to stay healthy for an extended period of time.

Malnutrition can occur when a person does not eat enough or uses up extra energy and nutrients. The problem is particularly acute in the sick and elderly. Malnutrition can also be caused by problems with chewing or swallowing.

When malnutrition is detected, the general practitioner should be called in. Family members or caregivers generally see the health problem before the patient does.

Symptoms of malnutrition

Malnutrition is a lack of energy or nutrients. This then leads to a lower weight and worse functioning of the body. This is mainly due to a decrease in muscle mass and a shortage of proteins, essential fatty acids, vitamins and minerals.

The largest groups at risk of malnutrition are the frail elderly, the chronically ill, people with cancer, people undergoing major surgery and people with severe trauma.

Causes of malnutrition:

  • reduced food intake due to loss of appetite or nausea.
  • difficulty in chewing, tasting, swallowing or digesting.
  • psychological problems, such as anxiety, depression, sadness. A person may no longer feel like eating. One result is skipping meals or taking smaller portions.
  • social factors, such as loneliness, no possibility of buying or preparing food.
  • dementia.
  • addiction.

The main risk factor for malnutrition is disease. Illness can also increase the need for nutrients so that a normal diet is no longer sufficient.

Malnutrition in the elderly

Elderly people have a higher risk of malnutrition because they are sick more often and exercise less. In addition, the elderly need less energy than when they were younger, which can make it more difficult to get all the nutrients in the diet.

Diagnosis of malnutrition

The first step is to determine whether someone has an increased risk of malnutrition. This is determined with a screening instrument. These instruments check for unintentional weight loss, underweight and loss of appetite.

If, on the basis of the screening, someone is at increased risk of malnutrition, it is determined whether someone is malnourished. A consensus was drawn up for this in 2018. Someone is malnourished if they meet at least the criteria of one of the characteristics and causes listed below.

One or more of these characteristics must be present:

  • Unintentional weight loss: 5% or more unintentional weight loss in the past 6 months or 10% or more unintentional weight loss in a period longer than the past 6 months.
  • Low BMI
  • Reduced muscle mass

One or more of these causes must be present:

  • Nutrient deficiency: 1 week of eating more than 50% less than the energy requirement or more than 2 weeks of reduced intake or absorption or a chronic gastrointestinal disorder adversely affecting intake or absorption
  • Disease or inflammation: acute disease or trauma or chronic disease-related inflammation

If someone is malnourished based on the above criteria, the severity of the malnutrition is then determined. People who are healthy or overweight can also be malnourished. Acute loss of nutrients through vomiting or diarrhoea can cause rapid deterioration in nutritional status, especially if there is also an increased energy requirement due to illness or fever.


For children, other cut-off values apply. The doctor will use growth curves to determine malnutrition in a child.

Effects of malnutrition

Malnutrition has a major impact on health. The consequences include:

  • slower recovery from surgery or illness
  • more and more serious complications after surgery
  • delayed wound healing
  • increased risk of bedsores (pressure sores)
  • impaired functioning of the immune system
  • reduced muscle mass
  • reduced heart and lung capacity
  • lower quality of life
  • increased risk of death

Identifying malnutrition

It is very important to immediately call in the GP when malnutrition is suspected. This is more often done by family, acquaintances or carers (informal carers) than by the patient himself.

Nutrition advice

In the treatment of malnutrition, emphasis is placed on sufficient intake of protein and energy. In addition, exercise is an essential part of the treatment to maintain muscle mass.

Is there a question of malnutrition? Then the health insurance will reimburse a number of hours for a dietician.

Depending on the severity of the malnutrition, a doctor and/or dietician can decide on an energy- and protein-rich diet, possibly supplemented with vitamin and mineral supplements, extra drinking food or complete drinking or tube feeding.

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