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What You Need to Know About Underweight Children

Medically reviewed by Jobelle Ann Dela Cruz Bigalbal, MD · General Practitioner

Written by Ruby Anne Hornillos · Updated Jul 04, 2020

What You Need to Know About Underweight Children

Children need to eat a healthy and balanced diet to grow strong. However, despite many parents’ efforts, a great many children around the world are underweight. “Is my child underweight?” you might wonder. 

Here is a quick look at what you need to know about underweight children. 

The Health Risks of Being Underweight

The majority of medical research on weight and how it affects our health focuses on the dangers of obesity. However, being underweight poses health dangers too, especially for children. 


A primary example of the dangers of being underweight is malnutrition. Malnutrition can stunt a child’s development and growth. Along with malnutrition, a child can also get anemia which can cause many other health issues. 

One study shows that malnourished children had lower IQs and performed poorly when tested on memory, learning, and attention.

Vitamin Deficiencies

An underweight child may have vitamin deficiencies that can create other problems. For instance, due to a lack of calcium and vitamin D, a child can develop osteoporosis, which can greatly impact their development.

Weakened Immune System

Additionally, poor nutrition can weaken the immune system. Weakened immunity can make a child more susceptible to diseases and infections that could further stunt their growth and development. 


Malnutrition can keep children from reaching their optimum height and size. However, it is not only the body that is affected.

Is My Child Underweight? Signs to Look Out For

At times, it can be difficult to tell if a child is underweight. The best way to know if a child is underweight is by bringing him or her to a doctor. 

A medical professional can determine if a child is getting what he or she needs for his or her development. They may use tools such as a BMI, or body mass index, and other tests to determine if a child is underweight. 

Even on your own though, there are a few ways to determine if your child is simply on the slim side or underweight.

For instance, if a child has “lean genes” because their family is slim, there is a good chance that they are naturally built that way. A child may also have a slender frame, which can make them lighter than other children their age or height.

Keep an eye out for certain signs that could signal that your child is underweight. For instance, an underweight child may often get sick due to a weak immune system and take longer to recover from illness. 

As mentioned earlier, vitamin deficiency is common in underweight children. Some vitamin deficiencies that can make them tire quickly are iron deficiency or vitamin B12 deficiency

A parent can also monitor a child by taking note of their weight.  If a child’s weight stays stagnant or decreases, a visit to the pediatrician would be a good idea. A parent may also need to visit a pediatrician if they notice that their child does not outgrow their clothes after a few months. Additionally, prominently visible ribs could be a good sign that a child is underweight. 

Why a Child Becomes Underweight

The most common reasons why a child is underweight is his or her diet. If the child eats too many unhealthy snacks and skips meals, he or she may suffer from malnutrition. 

Additionally, the child may not have the right type of meal plan. Most kids have small stomachs, which means they cannot easily fit their daily recommended calorie intake within three meals.

Therefore, they need healthy snacks throughout the day to help them get the right amount of calories.

6 Healthy Superfoods for Toddlers

Certain disorders or diseases could also keep a child from gaining weight. For instance, hyperthyroidism can cause a person to lose weight. The only way to truly determine if a child has a condition that is keeping them from gaining weight is by consulting a doctor.

Eating disorders could be another reason a child is underweight. This occurs more commonly in adolescents and teenagers than young children because of things such as bullying, or social media concerns.

An example of an eating disorder that can cause weight loss is bulimia, which is a potentially dangerous disorder where a person binge eats then purges. Another disorder is anorexia nervosa. If you suspect that your child has an eating disorder, you need to get professional help immediately as it is both a mental and physical issue.

How to Help A Child Gain Weight

A doctor can help create a meal plan to help a child gain weight. Adding more healthy snacks and smaller meals to a child’s diet can help them increase their calorie intake and help boost their health. 

It would be best to avoid loading up your kids on unhealthy, fatty foods. While those foods may be higher in calories, they could still leave kids malnourished and still underweight.

Bringing your child to a doctor can help you raise kids with healthier eating habits.

Learn more about child health, here.


Hello Health Group does not provide medical advice, diagnosis or treatment.

Medically reviewed by

Jobelle Ann Dela Cruz Bigalbal, MD

General Practitioner

Written by Ruby Anne Hornillos · Updated Jul 04, 2020

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