Tips for Helping Underweight Kids (and Their Parents)

Parents of underweight kids who really don’t eat enough deserve better help than they often get. Still, most of the time when people say to me that their child is skinny and a very picky eater, the child does not need to eat more. When kids do need to catch up on weight growth, slower is better than faster. Even though we are eager to get them back on the curve, for long term health it’s generally best just to be moving in that direction.

Before focusing on trying to pack on the calories, be sure

  1. They really are underweight (for their height)
  2. It’s not for medical reasons that need to be addressed

Remember, the goal is to add calories, while still preparing them for long term healthy eating patterns — this means doing it without processed white flour or added sweeteners or fried foods.

Fats have the highest calories. Add fat (olive oil, peanut butter, avocado, cheese, butter, etc.) to healthy foods (veggies, whole grains, lean protein sources — you can gradually wean back the added fats later, just like switching from whole milk to 2% to 1% to nonfat).

Liquid calories are less likely to fill you up — smoothies and shakes and juices are great for this. I prefer using real food ingredients, not a chemistry set (like you might find in some manufactured versions). e.g. Whole fat dairy or soy. Add an oil. Add fruits. Maybe peanut butter. (note: getting rid of unnecessary calories in drinks is one of the best ways to help overweight kids. Liquid calories sneak in.)

When eating is restricted, I recommend a multivitamin, multi-mineral supplement, with DHA, as spackle to fill in any nutrient gaps.

Periactin, an allergy medicine, can be a potent appetite stimulant. It can be a godsend, helping kids with no appetite suddenly start eating 3 meals a day. For kids in the first 2 1/2 or 3 years of life – when long term flavor preferences are forming, and kids need multiple experiences with a wide variety of whole foods — I’d try the medicine sooner rather than later. These are precious months for food experiences, and should not be wasted.

Published on: August 13, 2010
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Dr. Greene is a practicing physician, author, national and international TEDx speaker, and global health advocate. He is a graduate of Princeton University and University of California San Francisco.
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Recent Comments


Great article! My daughter is 16 months old and has struggled with eating enough since birth. She was below the 1st percentile in weight for months, and is now at the 3rd percentile. We have tried many strategies with her and she takes Pediasure now, but nothing has seemed to work to get her interested in eating more. Our pediatrician did not recommend an appetite stimulant, but I think it may be worth trying. My question is, how do you determine the weight for height percentile? And when is it cause for concern? My daughter currently weighs 7.85 kg and length is 78 cm.

I have a 9 -year -old girl she is 4 foot 4 inches and weighs 50 pounds and has for a while, she is on ADHD meds, but her eating was poor way before that. Her face is very thin and she is nothing but bones. Ant help will be appreciated, She takes Boost 3X a day for 2 years now but it doesn’t help.I even suspect she is anorectic.She only eats a few bites of food at a time mutable times a day. What should U do her doctor says nothing about it, ty

Hi Ellen,
Thanks so much for writing!
Anorexia is possible in prepubescent children. If that is the case, the earlier you treat the better. Look for an eating disorder program in a hospital near you for an evaluation and treatment if needed.
Hope that helps!
Alexandra (caring helper at, not a doctor)

Hi Dr,

I have a son, now just turned 9 yrs old who is in need of some help. He weighs 47 lbs. now but has only gained 4 lbs in 4 years. Since birth he has had eating issues and has never been over the 5%-tile and most of the time is 15-20% below the growth chart for weight vs height. First off, he is allergic to many foods limiting his choices and secondly, he has never been able to eat more than a few bites of food at a time and honestly does not care whether he eats or not – he could go all day and not ask for anything. My problem is mainly that doctors and nutritionists are not getting us past the “just try to get him to eat more” or “try to add calories to his meals” phase. We changed pediatricians due to a move and the new doctor was not curious enough about my queries to look into possibly prescribing something to stimulate his appetite. Doctor says “he’s just skinny.” Son has always complained about his stomach hurting when he eats. He also has developmental delays in school, and has more recently complained of tiredness, legs hurting, etc. so I am getting more concerned. I have 4 other children who have all been normal growth curves and getting them to eat is literally a pc of cake, but this one does not have the normal hunger urges… hope that makes sense. Any advice?

As a doctor your child seems to me to be suffering from IBS or coeliac. INSIST HARSHLY on a complete checkup from your general practitioner. Complete blood count, esr, lft, renal tests, stool tests, the full workup, as well as blood markers for ibs and coeliac, sometimes its the hidden clues like the child has learnt to avoid bread or milk in cases of lactose intolerance. Good luck


Dr. Greene has written an answer to your question. You can find it here –> Stunning New Techniques to Increase Calorie Intake for Picky Eaters.

Best, @MsGreene
Note: I answer a lot of questions on, I am the co-founder of, Dr. Greene’s business partner and wife, but I am a not doctor. Please keep that in mind when reading my comments and replies.

Good day doctor, is it ok to give mosegor to a 6 years old to boost his appetite? Thank you

My 13 year old son weighs 70lbs is in good health, does well in school and plays soccer BUT he is a very picky eater and can only eat small amounts at a time. He has always been small and thin but now all of his friends are having growth spurts and going through puberty while he is Not growing much or not starting to go through puberty at all yet. His 2-3 lb a year weight gain is a becoming a real problem. We have tried everything, appetite increase vitamins which made him throw up and trying to offer him food as often as we can but he just doesn’t seem to want to eat and can’t gain weight. He really wants to gain weight and grow and says that he thinks he has a disease or some sort of condition. Is there anything you can suggest That would help him eat more? Maybe a daily appetite increase pill or a food physicologist? ( is that even a thing?) we are at our wits end. He starts high school in 6 months and I’m concerned that he will be become depressed.

What is the youngest age to start Periactin ?
My 15 month old daughter is on 2percentile for weight but her height and head are ok at about 50th percentile.
She eats less than a newborn in a day and refuses almost everything after 2-3 small bites.

Hi, my name is Trudy, my little girl(7 years) is underweight after complaining about worms, stomach pain now and then and stomach pain after urinating sometimes,i took her to the doctor but nothing helped. what can I do….please help.

I am not joking when I say my 3.5 year old boy is afraid of food. He has weighed only 29 lbs for the last 8 months. Lately it has gotten worse. We have tried Periactin and it works but my child’s behavior becomes intolerable on this medicine. We live a somewhat healthy lifestyle; eating whole wheats, fresh fruits and vegetables, lean protein-rich meals, etc. My boy will only eat/drink milk products sometimes. His calories amount to no more than 600 daily average. We are going to see the pediatrician but are there any other suggestions? This is so stressful. We literally chase him around the house offering food. At this point we just want him to take in a few more calories.

is periactin a prescribed medicine or OTC

Hi Alba,

I’m so sorry you and your son are going through this. There is help! Feeding specialists can work with him to determine why this is happening and give you tools to help him over come his fears.

You will need to find someone who is local to you, but consider reaching out directly to Melanie Potock, MA, CCC-SLP, Coauthor of Raising a Healthy, Happy Eater: A Parent’s Handbook A Stage-by-Stage Guide to Setting Your Child on the Path to Adventurous Eating and founder of & and / or Beth Bader is the coauthor with Ali Benjamin of the acclaimed book, The Cleaner Plate Club.

Hope that helps,

Is periactin available over the counter? I would like to purchase it for my 36 month old daughter. She should be 3 November. She does not have appetite from the time she was a baby. She is underweight and grows slowly. However she hates eating, especially things with calories. Plus she prefers to drink than eat and she doesn’t like to drink milky products. Is periactin available in Jamaica?

Hi shan, is your baby still doesn’t want to eat? i think i have the same problem with you,may i know what do you do to make your doughter eat? (if she can take any food now) thanks before