My first little girl is one of the biggest reasons I started helping families five years ago.

I experienced motherhood with an underweight child who just wouldn’t gain weight or grow.

My daughter was 4.5 pounds at birth and every single day for the next few years of her life, her weight consumed me.  I chased her around the house with a spoonful of food. I packed snacks with me everywhere I went.  I let her eat in front of the iPad and while I distracted her with toys. She was BELOW the 0 percentile on the growth charts and labelled as failure to thrive.

That’s a term that no parent wants to hear, because I know how it impacted me.  I interpreted her failure to thrive to mean that I was failing her as a mother and a nutritionist.

Her weight was also the reason I created this long list of 60 High Calorie, High Nutrient Foods for underweight kids.

Having an underweight child makes feeding our children so much harder and much more stressful.  You’re always wondering, ‘What if he/she isn’t getting enough calories?”.

Those weigh-ins at the paediatrician’s office were the WORST memories for me as a mother. I left in tears 80% of the time.

But that was 5 years ago and thankfully, we are in a much better place.  My daughter is no longer failing to thrive – in fact she is thriving in every aspect of her life (except for bedtime – she hates going to bed that little bugger!).

Here’s my daughter getting measured at the age of 3.

underweight children

Here’s my daughter getting measured this year (at the age of 6!).

As a mom of an underweight child, I wanted to touch on this subject, because it’s near and dear to my heart.  And many parents I work with are worried because they are in my former shoes.  With a child who doesn’t gain enough weight.

We know that children come in different shapes and sizes and grow at different rates.  A child at some points during their growth may be taller, shorter, heavier, or lighter than other children their age and that is usually a-okay!

Keeping track of a child’s growth is important because it can tell us a lot about their health.  If a child is growing too fast or too slow, this may be a sign that there is something going on with their health and/or nutrition.

But please don’t become obsessive about it or even do it at home.  That should be the responsibility of your child’s healthcare provider.

Understanding the Terminology:

There are so many different terms that are used for a child who is underweight such as failure to thrive, malnourished, SGA, and smaller than normal. We know it can easily get overwhelming and so I wanted to take the time to simplify it all.


According to the Cleveland Clinic, a child who is considered to be underweight is a child who is in the bottom 5th percentile for weight compared to their height.

Failure to Thrive:

A child is considered to be failure to thrive (FTT) according to HealthLink BC if they seem to be growing in height and weight at a slower pace compared to other children of his or her age and sex.  However, it’s the other symptoms that can suggest a child is FTT:

  • Not enough weight gain for age
  • Low height (or length, if a baby) for age
  • Irritability
  • Tiredness
  • More sleepiness than normal
  • Lack of age-appropriate social response, such as smiling
  • No vocal sounds
  • Delayed physical movement changes (motor development)
  • Learning and behavior problems in older children

According to Stanford’s Children’s Hospital:

A baby or child with an ongoing (chronic) health condition may also need more calories and nutrients than normal.  This may be the case with congenital heart disease or a genetic syndrome. – Source

Our daughter had both factors that contributed to her FTT diagnosis – Russel Silver Syndrome (a genetic condition) and a VSD (Congenital Heart Disease).

IUGR: Intrauterine Growth Restriction (IUGR)

Another term you may have heard for IUGR is fetal growth restriction. IUGR is a condition where the fetus is smaller than anticipated for the number of weeks of pregnancy. According to Standford Children’s Health, a child with IUGR is usually seen to weigh less than 90 percent compared to all other fetuses at the same gestational age. This is not to say that all fetuses’ with IUGR are born prematurely, some can be born at term as well (after 37 weeks of pregnancy).

Small for Gestational Age:

Small for Gestational Age (SGA), is a term used when describing an infant who is considered smaller than usual for the number of weeks the mother is pregnant. A baby who is SGA is usually seen to have a birth weight lower than the 10th percentile for babies who are of the same gestational age.

What’s interesting is that an infant with SGA can seem physically and neurologically mature however they are always seen to be smaller compared to other babies of the same age.

Our daughter was also considered SGA.

Children feeding and growth challenges

Understanding Growth Charts

I have a love/hate relationship with growth charts because they make many parents feel inadequate and are a significant source of stress.  But on the flip side, they are a necessary tool for health professionals to assess a child’s health and growth.

There are two sources of growth charts. Let’s take a peek at both…

World Health Organization (WHO):

The World Health Organization has created its own set of standards and growth charts to determine if a child is underweight.

The indicators that they have developed include the following:

  • Length/height-for-age
  • Weight-for-age
  • Weight-for-length/height
  • Body mass index-for-age (BMI-for-age)
  • Head circumference -for-age
  • Arm circumference-for-age
  • Subscapular skinfold-for-age
  • Triceps skinfold-for-age
  • Motor Development milestones

The WHO growth chart should be used for infants and children between the ages of 0 and 2 for the following reasons:

  1. They establish the growth of the breastfed infant as the norm for growth
  2. They consider physiological growth in infancy

Center for Disease Control and Prevention:

The Center for Disease Control and Prevention Standards (CDC), has also created clinical growth charts. These growth charts are best used for children and adolescents between the ages of 2 and 20. These growth charts include details such as:

  • Stature-for-age
  • Weight-for-age
  • BMI-for-age

So why isn’t your child growing?

There could be a few reasons why your child is underweight. Here are some of the most common ones:

1. Low Calorie/Fat intake

Our little ones grow up so fast, that sometimes it’s hard to keep up!  One way to ensure their calorie intake is high enough is by serving lots of healthy fats (avocados, olive oil, coconut, etc). Kids need a lot of fuel. They are bouncing balls of energy!

Nutrient dense foods for underweight kids

2. Poor Digestion

A child with digestive issues will have more stomach aches, indigestion, and lower absorption of nutrients from their foods. If your little one is uncomfortable after most meals and is also underweight, digestion may be the cause. Who wants to eat when their tummy hurts?!

One of my most recent clients has a two-year-old boy who had eaten very little and wasn’t gaining weight.  After removing gluten from his diet he gained 3 pounds in just a few weeks!  Hence, it’s worth looking into the foods they are consuming and identifying any food sensitivities or allergies that could be driving this.

3. Bowel Disorders

Some children who are underweight may suffer from bowel disorders or digestive diseases such as gastroesophageal disease or inflammatory bowel disease.  These conditions can lead to weight concerns because they are not able to eat effectively, and if they do, it immediately is expelled from their bodies.

4. Oral Motor or Sensory Processing Issues

If you’ve seen my Free Webinar (10 Proven Picky Eating Strategies), you know that eating is one of the most difficult tasks we do as humans. It’s more difficult than walking or talking!  It uses all 8 senses and multiple muscles and nerves.  So if a child has trouble processing the sensory inputs from food (i.e. the smell is too strong) or they can’t manage chewing foods due to low muscle tone or poor chewing mechanics (the tongue is a muscle!) then they may avoid eating to avoid discomfort/anxiety.

Knowing the reason why your child is struggling with weight gain can help you get to a solution faster.

Concerns with being underweight

Helping your child through nutrition will be key in helping them overcome weight concerns. Here are some great techniques to use during mealtimes to ensure your child is eating enough of the right foods:

  1. Incorporate healthy fat sources at every eating opportunity (here are some ideas)
  2. Opt for quality proteins that are critical for growth.  Especially grass-fed meat products and/or wild fish and/or free-range eggs which are cleaner sources and contain more nutrition.  Every bite counts for our little ones.
  3. Include fiber at every eating opportunity. Foods like sweet potatoes, squash, carrots, beets, and parsnips are wonderful nutrients and more calorically-dense carbohydrates that will give your child the energy they need.
  4. Avoid grazing.  Research shows that toddlers consume 50% fewer calories when they graze (in comparison to their peers with structured mealtimes).
  5. Try a gentle elimination diet with the help of a healthy professional to determine if there are any food intolerances at play.
  6. Hire a health practitioner to give you a clear plan to help improve your child’s weight.

Is your child underweight?

Tell me more in the comments.