What are the risks of being underweight?

Just like it is with obesity, being underweight also poses many health risks to an individual.

Scientifically, one cannot be termed as underweight by the way they look or appear physically, rather, health experts say, measurements should be taken to confirm that a person is underweight.


Private Kamanzi, a nutritionist and dietician at Amazon Clinic Cabinet in Remera, says being underweight is a condition where one does not have the appropriate weight to match to their height.

He says body mass index (BMI) is used to determine if one is underweight, at a healthy weight, or overweight.

“Using the BMI is considered a good measure of a person’s weight because it compares their weight to their height,” he says.

For adults, he says, people from 20 and above, the weight is taken in correspondence to their height where the BMI is calculated; if it’s bellow 18.4, the person is considered to be underweight.

BMI is an indicator of the proportion of weight and height.

Still, in adults, Kamanzi says being underweight is brought about by many factors, but the most common one is a poor diet, especially for those people who don’t get enough protein and carbohydrates.

Underweight malnutrition is normally protein energy malnutrition, meaning that if one is underweight, it’s due to low calorie intake.

He explains that underweight malnutrition is normally protein energy malnutrition, meaning that if one is underweight, it’s due to low calorie intake, which includes protein.

“It can as well result in some conditions that disturb the metabolic rate, malabsorption and also cut down the appetite to eat,” he says.

Joseph Uwiragiye, head of nutrition department at University Teaching Hospital of Kigali (CHUK), says in children and teens, BMI is used to find out if a child or teen is underweight, of a healthy weight, overweight, or obese. A child’s body fat changes with age. BMI for children includes gender and age.

This, he says, is according to the points that have been made by the World Health Organization (WHO).

He notes that this is when the weight of the child does not correspond with their age, and there is an indicator known as ‘Z score’ which is normally used to confirm this.

“When the measurement for a child is done and the head score for weight and age is above negative two, this indicates that that particular child is underweight,” he says.

Uwiragiye says there are moderate and severely underweight children.

Severely underweight, he says, is whereby the age and weight do not correspond and, there is another condition such as diarrhoea or vomiting.

In adolescents, BMI for age is taken and when it’s under 50 per cent, then one is considered to be underweight.

When a person is underweight they get sick often and it happens because they do not get enough energy from their diet to maintain healthy body weight. /Net photos


Janvier Rusizina, a general practitioner at La Nouvelle Clinic in Remera, Kigali, says being underweight can cause health problems.

He says that not all people who are underweight experience adverse side effects or symptoms.

However, some people experience symptoms such as persistent fatigue and illness, among others.

When a person is underweight, Rusizina says, they get sick often and it happens because they do not get enough energy from their diet to maintain healthy body weight. They also do not get enough nutrients to fight infections.

As a result, he says, such people may get sick more frequently, with common illnesses, such as a cold that can last longer than normal.

Dr Iba Mayale, a gynaecologist at Clinic Galien in Remera, says women can experience irregular periods.

He explains that women who are underweight may not have regular periods. For instance, he says they may find menstruation stops, or an adolescent’s first period may be delayed or absent. This irregularity can lead to infertility in some cases.

Mayale notes that if a pregnant woman is underweight, she can also experience premature childbirth.

He says that a woman who is pregnant and underweight is at a higher risk of pre-term labour, which means that the possibility of having a baby before 37 weeks is very high.


Kamanzi says there are many effects that come with being underweight, the most common being weakened immune system, which makes one susceptible to diseases, like diabetes.

Francis Kazungu, a general practitioner in Kigali, says that people aren’t aware of this; in fact, some of them assume that when one is skinny, they are healthy. He says it’s not only obesity that exposes one to diabetes.

He explains that diabetes comes from insulin resistance, which causes high blood sugar. He adds that while about 80 per cent of people with diabetes are overweight or obese, it happens to thin people as well.

One of the reasons he says is due to the weakened immune system and also ‘skinny fat’ which exposes them to type 2 diabetes.

‘Skinny fat’ is a slender body type with small amounts of visible fat. Skinny fat people tend to have a type of fat called visceral fat which grows around their organs instead of under their skin, thus being invisible.

Kazungu says the working capacity of people who are underweight is also impacted in a negative way because they are not strong enough.

Doctors advise to maintain a healthy diet. 


Maintaining a healthy weight, Uwiragiye says, should be done in moderation.

Understand how many kilogrammes one needs to gain depending on their current weight.

He adds that one should know the weight they shouldn’t exceed.

However, he notes, this can only happen if one consults with a nutritionist to follow the right diet.

“There is a diet for people who are underweight, and an ordinary person is not in a position to know what to take or consider to gain normal weight,” he says.

He says in some cases, underweight people end up gaining more weight than they should.

Additionally, Uwiragiye says, after helping one reach the required weight in a healthy way, experts should be in the position to help them adjust their diet so that they maintain healthy weight.


It’s ideal for parents to always seek help from nutritionists on how to feed babies. Sometimes what they think is right is actually not, and doing this for a long time can have a negative impact on the general wellbeing of the child.

Joseph Uwiragiye, Nutritionist


Getting screened for chronic illnesses is important because some people might fail to gain weight in a healthy way due to an underlying illness that they aren’t aware of.

Ivy Kamugisha, Medical student


Anaemia can also be the cause of weight gain or loss. This is due to low blood count which has symptoms like dizziness, headache and fatigue. Seeking medical help can help rule out such conditions.

Immaculate Kiiza, Nurse


Maintaining a healthy diet is crucial, especially for young people, to avoid obesity which is common among children nowadays. Involving children in physical activity is also important when it comes to their health.

Dr Bandora Iraguha, Gynaecologist