Is Your Skinny Kid “Constitutionally Thin”?

Submitted by on December 10, 2013 – 1:42 pm2 Comments
skinny kids constitutional thinness

Genetic predisposition to constitutional thinness may not be immediately obvious. Look beyond the parents at your extended family.

… and what does it mean?

When one of our nutrition experts recently spoke about a child being “constitutionally thin”, I figured this must be nutritionist speak, as I had never heard the term. Given how many of our readers write in with questions and concerns about their skinny kids, I know parents are curious to know more. So, I sat down with ZisBoomBah’s own Lisa Lanzano, MS, RD to dig deeper. Constitutional thinness is an actual clinical condition. Learn more about the diagnosis from our expert.

A child who is constitutionally thin usually has a low but stable (not fluctuating) body mass index (BMI) without any hormonal abnormality, malnutrition or other health concerns that would explain her low weight. (To learn what is a healthy BMI for your child, visit the Centers for Disease Control and Prevention website.) Though constitutional thinness is very different from anorexia nervosa, the condition is not without risk (e.g., low bone mineral density could be a concern). What’s more, it is important for your pediatrician to skillfully distinguish between your child being constitutionally thin and being at risk for developing an eating disorder. 

Read: Picky Eating or Eating Disorder? Know the difference and when to get help 

Essentially, constitutional thinness is a clinical diagnosis, after all other issues appear normal, including your child’s psychological profile. “Look for an obvious genetic link,” Lisa advised parents who may be concerned. Genetic predisposition, however, may not be immediately obvious. Look beyond the parents and at your extended family; a skinny uncle your haven’t heard from in a decade?

After you have ruled out any health issues with your constitutionally thin child and you still need your skinny kid to put on a few pounds, Lisa has great tips on healthy weight gain.

How to help your skinny kid gain weight — the healthy way

10 Common Food Rules — Flipped for Skinny Kids

Skinny Kids: Daily meal add-ons and snacks for healthy weight gain 

How to Help Skinny Kids With Food Allergies Gain Weight 

Skinny Kids: Why whole-milk products and 100% Juice are better choices

Skinny Kids: How to boost meals for healthy weight gain  

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Categories: General, Guides, Skinny Kids


  • nichole says:

    Will my child’s body tell him what it needs?

  • Karen Laszlo says:

    The following is a response from Keith-Thomas Ayoob, EdD, RD, FAND, our contributing Nutritionist. If you want to learn more, please follow Keith’s twitter @KeithAyoob

    The real answer is yes and no. Young children CAN be very internally-driven, instinctive eaters, but this is not always reliable. Environmental issues, including availability of food, how food is presented, family temperament at mealtimes, even noise levels, but especially the approach to feeding by the parents and caregivers can override children’s internal drives. Keep in mind that we all like certain tastes and infants as young as a few days old have preferences for sweets, perhaps a genetic influence from when we had to determine what was safe to eat in nature, as sweet foods tended to be non-poisonous and even nutritious.

    Nowadays, kids need guidance and they need parents to provide that. Offer them a variety of nutritious foods for meals and snacks and don’t get too worried if they like one vegetable or fruit more than another, as long as they eat foods from each food group daily. Also, when introducing a new food, count on having to expose kids to it about 12-15 times before they really make up their minds about it. Most parents quit after a child refuses a food 3 or 4 times, but the research is solid here — kids take their time to decide. I’m a fan of having a rule that everything on the plate gets tasted. They can decide if they like it but even if they don’t, they need to taste everything. Remember also that parents are primary role models here, so be good ones about eating a wide variety of healthful foods. Kids learn what they see more than what they hear you tell them.

    Keith-Thomas Ayoob, EdD, RD, FAND
    Associate Clinical Professor
    Department of Pediatrics
    Albert Einstein College of Medicine
    1165 Morris Park Ave. 4th Floor
    Bronx, NY 10461
    718-430-3970 ext. 6412
    T: @KeithAyoob

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