Underweight

What is underweight?

Underweight is when people weigh less than is good for their health. That is easy to determine with the Body Mass Index (BMI). The BMI shows the ratio between weight and height. Assuming normal build, a BMI of less than 18.5 indicates underweight.

What are the complaints associated with underweight?

Being underweight can involve health risks. The person's condition may deteriorate and people may feel more lethargic and tired. They may feel dizzy easily and their hair will fall out more than usual. The body responds to reduced energy intake by burning fat reserves first, and that leads to weight loss. Once the fat reserves are depleted, other tissues and organs, such as muscles, the liver, kidneys, the heart and nervous system, can also be affected, causing a range of physical complaints.

The risk of osteoporosis (bone decalcification) and fractures increases. The physical symptoms of an underweight person are similar to those of someone suffering from malnutrition due to anorexia nervosa.
People with intellectual disabilities sometimes find it impossible to communicate these symptoms. The people around them may then notice only a change in behaviour.

How common is underweight in the general population?

About 2% of adults in the Netherlands are underweight. Children are more likely to be underweight: 16.6% of boys and 15.3% of girls between the ages of 2 and 6 years are underweight. ¹⁰⁰

How common is underweight in people with intellectual disabilities?

The European POMONA questionnaire survey looked at a random sample of 1269 adults with intellectual disabilities and found that 15.7% were underweight. ¹⁰¹

An English study of 1119 adults aged 20 years and over with intellectual disabilities found a prevalence for underweight of 18.6% (underweight was linked to younger age and the absence of Down syndrome). ¹⁰²

Underweight diagnosed using the BMI is found in 3% of the older people with intellectual disabilities, which is comparable with older people in the general population. ⁴⁷¹

Sarcopenia is the loss of muscle mass, muscle strength and muscle function. The Dutch GOUD study found sarcopenia in 14.3% of older people above the age of fifty with intellectual disabilities. It is found in people with intellectual disabilities at a relatively young age, being associated with limited mobility, increased levels of inflammation and underweight. ⁴⁷²

A Norwegian study of 282 people with intellectual disabilities found a correlation with an increase in the severity of intellectual disabilities, as well as a refusal to eat and vomiting. ¹⁰³

A relationship has been found between underweight and swallowing disorders, and between underweight and physical impairment (such as spasticity). ¹⁰⁴

A study of 35 children with cerebral palsy found that 43% were malnourished. ¹⁰⁵
There is also a relationship between cerebral palsy, severe mental and physical limitations, and malnutrition. ¹⁰⁶

2% General population 15.7% to 18.6% People with intellectual disabilities