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Thin Body Type (Normal Slenderness)

What is normal slenderness?

  • The child looks thin or slender. Their weight is more than 20% below the ideal weight for their height. However, they are well-nourished, with a normal fat tissue layer (8-12 mm) as measured by a skinfold calipers. They do not need to gain weight.
  • Normal slender children are not actually underweight. Underweight children have a low fat tissue measurement and need to gain weight.
  • Normal slender children and underweight children both can have a low BMI.

What is the cause?

Children with a thin body type do not undereat. They have a normal diet and get the right amount of calories. Your child may have a thin body type if:

  • Your family is naturally thin.
  • Your child has a slender bone structure or frame.

How can I help my child?

  1. Reassurance: Make sure that your child knows that he or she has a normal thin body type and is healthy. Seeing some ribs is healthy. It’s called normal slenderness. Thin kids don’t need to see their healthcare provider or have any special tests. Your child doesn’t need to gain weight.
  2. Eating: Your child doesn’t need more calories. Eating more calories would add fat, not more muscles or bigger bones. A healthy child does not need to overeat. Trust your child's appetite center in the brain. It will make sure he eats enough calories for normal energy and growth.
  3. Meals: Serve well balanced meals and make mealtime pleasant. Talk about fun subjects unrelated to food. Avoid any comments or pressure about eating more. If your child complains about certain foods, or refuses to eat some foods, see the topic about picky eaters.
  4. Special foods: Special high calorie drinks or foods are not helpful. Neither are any pills that promise to build muscle or put on weight.
  5. Exercise: Encourage physical activity. This will improve your child’s strength, endurance, muscle mass and confidence.
  6. Bully-proof: Even though children know that they are healthy and look good, some teasing is to be expected. Help your child rehearse a reply, such as “Yep, I’m all muscle and bone, lean and mean”.

When should I call my child’s healthcare provider?

Call during office hours if:

  • Your child loses weight.
  • Your child does not gain weight for over 6 months.
  • You and your child argue about food or mealtime becomes a battleground.
Written by Barton D. Schmitt, MD, author of “My Child Is Sick,” American Academy of Pediatrics Books.
Pediatric Advisor 2019.4 published by Change Healthcare.
Last modified: 2012-05-15
Last reviewed: 2018-07-13
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright ©1986-2018 Barton D. Schmitt, MD FAAP. All rights reserved.
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