Promoting Healthy Weight Gain In Your Underweight Teen: A Guide for Parents

Key Facts
  • Your teen should be evaluated by their primary care provider to make sure they do not have an underlying medical condition that is causing the weight loss.
  • An evaluation by a Registered Dietitian is often very helpful.
  • Gaining 1-2 pounds a week can be a safe and healthy goal.
  • Young men's version of this guide


Some teenagers have difficulty keeping up with the energy needs of their bodies and, as a result, may be underweight. While there are medical reasons this could be happening, it could also be that they are growing taller, exercising a lot, are too busy or distracted to eat appropriately-sized meals, or they may simply have a high metabolism (the way our body burns calories). Growing during the teen years requires more food energy than at other times of life. Teens can lose weight when they are burning more calories than they are taking in. Teens grow at a different pace than their siblings or friends, and each teen will experience different periods of fluctuating weight. Your teen may follow a growth pattern similar to your own when you were their age.

This guide is not intended to help parents of teens who suffer from an eating disorder or other medical condition(s) that can cause significant weight loss. If your child has been diagnosed with an eating disorder or you suspect that your teen might have disordered eating, please refer to:  Understanding Eating Disorders: A Guide for Parents and Families. As there are many reasons it could be happening, if you are unsure of why your teen is underweight please consult with your child’s medical provider for an evaluation.

What are the medical implications of my teen being underweight?

Sometimes, a teen who is underweight may not be getting balanced nutrition. They may not be getting enough vitamins, minerals (such as iron and calcium), protein, or dietary fat from food to support a healthy, growing body. For example, a growing teen needs plenty of calcium and vitamin D to make and maintain strong bones. If a female is significantly underweight, she may not have regular periods. Lack of periods are usually due to low estrogen levels which can cause loss of bone mass and eventually put a teen at risk for osteoporosis. Additionally, when a teen is expending more energy than they are taking in, the body’s fat reserves are disrupted which can compromise the immune system making them more susceptible to acute and chronic medical conditions.

Unintended weight loss is an important reason to be evaluated by a health care professional. Sometimes there is an underlying medical problem that is responsible for weight loss. Thus, it is very important to talk with your child’s primary care provider about your concerns. Call right away if they have any of the following symptoms: fever, vomiting and/or diarrhea, cough, ear pain or sore throat, decreased urination, and/or increased sleepiness.

How often should my teen be eating?

The goal is 3 meals and 2-3 snacks daily (trying not to go longer than 4 hours without eating). Don’t worry about variety when initially trying to gain weight – the important thing when working on catch-up weight gain is getting in the extra calories. Once you’ve found things that work for you and your teen, stick with them.

What should my teen add to meals and snacks to boost energy and calories?

There are simple and tasty ingredients that can be added to meals and snacks to help with weight gain. The goal here is to increase the energy of your teen’s meals and snacks without only relying on increasing the portions, which can sometimes be an overwhelming change. Here are some ideas:

  • Add butter or oil to food. For example, at breakfast, spread a generous amount of butter or margarine on bagels, toast, English muffins, or an egg sandwich. At lunch and dinner, use butter/margarine when cooking. Top warm veggies with a couple of teaspoons of butter or olive oil; it will blend right in and won’t change the flavor too much.
  • Use whole fat dairy products such as whole milk, full fat or regular cheese and yogurt, instead of skim, reduced fat, or low fat dairy products. For example, suggest that your teen put whole milk on his or her cereal or oatmeal at breakfast. At lunch, suggest using regular, full-fat cheese in an omelet or on a sandwich or burger. As a snack suggest a whole milk yogurt with granola and nuts. For dinner, try melting cheese or adding a scoop of sour cream to baked potatoes, or sprinkling parmesan cheese on veggies or any entrée. Additionally, offering a glass of whole milk with each meal can be helpful. And encourage your teen to enjoy a generous scoop of regular ice-cream instead of low-fat or frozen yogurt for an energy-dense snack option.
  • Modify Cooking: Use heart healthy oils such as olive oil or canola oil, and add nuts or nut butters when preparing and cooking food. Experiment by adding almonds, walnuts or cashews to salads or a stir-fry, trail mix, or cottage cheese. Try all-natural peanut butter on celery, crackers, or in a peanut butter and jelly sandwich as a wholesome snack.
  • Use “Extras”: These are items added to foods and drinks to enhance flavor and energy. For example, mix Carnation Breakfast Essentials® powder into a glass of whole milk, a yogurt smoothie, or a milk shake. Add dried fruit or granola to yogurt, chop a hard-boiled egg into salad, or add chopped avocado to tuna or chicken salad. Mix nut butter into yogurt, oatmeal, smoothies, or ice cream.
  • Maximize Portions: You may also wonder how much food to offer your teen at meals and snacks. Paying attention to portions can be helpful for weight gain. First, think about how much your teen eats for most of his or her meals and snacks. Slowly try to increase the overall volume of food at each meal, starting with one meal. For example, try adding one food item to your teen’s typical breakfast. Once portions have increased over a few days at breakfast, focus on adding to dinner or lunch. Do the same with snacks. For example, instead of two small cookies, offer 3 or 4 small cookies with a glass of whole milk.

How quickly should my teen gain weight?

Usually 1-2 pounds per week is a safe and healthy weight gain goal. Most people do not gain exactly the same amount of weight per week. As long as the overall trend during the course of several weeks to a month is weight gain, your teen is moving in the right direction. Their medical team will let you know if the pace is too fast or slow.

Should I check my teen’s weight at home?

No. It’s usually a better idea to have your teen’s health care provider or dietitian check their weight at clinic appointments. Checking weight at home is generally not helpful and can be frustrating for everyone, especially if the weight isn’t going up. By having their weight checked in the office, the same scale is used and accuracy is ensured. Their medical team will let you know how often they need to return for weight checks and whether or not it is necessary to check their weight at home. Often weight can be checked without needing a full medical visit, if needed.

Can my teen gain weight if they are vegetarian?

Yes. Teens can gain weight if they follow a vegetarian diet. Most vegetarian diets are naturally lower in calories, because they tend to contain more fruits, vegetables, and lower fat protein foods such as beans and tofu. However, by following the tips in this guide, your teen can gain weight and still make healthy vegetarian meal choices. There are lots of high-calorie vegetarian ingredients such as cheese, other whole-milk dairy products, coconut cream, avocado, oils, nuts, seeds, and nut butters.

Does my teen need special vitamins or mineral supplements?

A standard over-the-counter multivitamin with iron is a good idea for teens; these vitamins often provide the right amount of vitamin D too. The generic store brand is usually the same as a name brand, and it is often less expensive. Most gummy vitamins do not contain iron, so if your teen can swallow a pill, that would be the best option. If not, talk to provider to discuss which vitamin(s) would be the best for your teen. If your teen is eating enough calcium-containing foods (3 to 4 servings of dairy/day such as milk, yogurt and cheese), they probably don’t need to take a calcium supplement. In some cases, your child’s medical team may prescribe a specific supplement based on their individual needs.

Are nutritional supplements helpful?

There are nutritional supplements that are designed to help people gain weight. For example, liquid shakes such as Boost®, Ensure®, Soylent® or any generic version of these. Be mindful of protein shakes and other nutrition supplements marketed towards “fitness” and/or “dieting”. They are often designed for weight loss, which means they are high in protein yet low in calories. For your teen’s weight restoration, a supplement with adequate calorie and protein content is the most helpful.  Supplements may be useful if weight gain is not happening quickly enough after several weeks of increasing food portions and adding calorie-rich foods and “extras” to meals and snacks. Your teen’s health care provider will let you know if they needs to add supplements.

What should I do if my teen refuses to eat more?

Try to be patient. Sometimes it takes a while for teens to get on board with a new eating routine. Look at each addition as an accomplishment. You will see progress over time. A counselor or dietitian can help your teen if they are struggling with finishing the increased portions or if they are having trouble making dietary changes.

What if my teen compares her eating patterns to other family members?

Encourage your teen to avoid comparing their eating style to other family members or to their friends’ eating habits. In order to gain weight, your child will likely be eating more frequently and consuming larger portions than others. It is important that your teen understand that everyone has a different metabolism and different nutritional needs. At this time, it is necessary for your teen to eat differently in order to reach their full growth potential.

Do I need to make special meals for my teen?

No, but it will be helpful if you plan meals and snacks in advance. Include your teen when selecting food and have them help with grocery shopping and food preparation. At meals, select recipes that are easily modified. In some cases, you may be able to prepare two versions of a meal, for example: macaroni and cheese with extra butter for your teen; and the same recipe without the added butter for other family members. Remember, this is likely a temporary situation and you will not always have to make modifications.

Should I worry about reading food labels?

Reading the Nutrition Facts Label on food products is a good habit to adopt in general. This practice will help you identify health claims and the nutritional makeup of food items. Use this information to compare foods when grocery shopping. For example, you can look at different loaves of bread to find the one with the highest calorie slices. Look at protein, calcium, iron, dietary fat, and other nutrition information when making choices. Be sure to look at portion information as well. Generally, foods that supply the highest amount of calories and nutrients for the smallest portion size will help the most. However, try not to talk too much about calories with your teen.

Should my teen meet with any specialists?

A Registered Dietitian (sometimes called a nutritionist) who specializes in working with teens is a great part of the treatment team. The dietitian will make an individualized plan for your teen, taking the whole family into account. Your teen will learn specific ways to get the nutrition he or she needs to reach a healthier weight. Sometimes, one visit is all that is necessary to get on track. In other cases, follow-up visits are recommended until weight gain and health goals are accomplished. Your teen’s dietitian will set the pace for how often they meet, be it once a month, every other week or on a weekly basis.

A mental health counselor or therapist who specializes in working with teens may be helpful with goal setting and providing help with any anxiety related to food and health.

What are the best fluids to drink?

Energy-dense (or “calorie-containing”) fluids include: whole milk, 100% fruit juice, smoothies, milk shakes (including nutritional supplements or homemade milkshakes), and Carnation Breakfast Essentials®. Avoid calorie-free or low-calorie drinks such as diet soda, Crystal Lite®, or seltzer water. Your teen should drink at least 8 ounces of calorie-containing fluids with each meal and snack. Generally, calorie-containing fluids can help promote weight gain because they are relatively less filling than solid foods providing similar energy (calories).

What about protein bars?

Protein bars are another type of supplement. They come in many different brands and flavors. Bars that have a balance of carbohydrates, protein and fat are okay to have as a snack or part of a snack and can be a convenient way to have food available when on the go. Avoid bars that are extremely high in any one nutrient such as protein.

Are there any foods or fluids my teen should avoid?

Certain foods and drinks that lessen appetite and those with no nutritional value should be avoided. Encourage your teen to omit or decrease their consumption of caffeine and caffeine-containing products such as coffee, soda, and energy drinks. They should also avoid sugar-free, fat-free, and low-fat foods or following any specific diet “trend”.

How do I make sure my teen doesn’t gain too much weight?

Your teen’s health care provider will be checking their weight periodically. When weight maintenance is appropriate, you will be informed. Simply altering some ingredients (decreasing the number of servings of fruit juices or other energy-dense drinks) will help to reduce the amount of daily calories if necessary. Working with a dietitian can help with the transition to weight maintenance. It is very important to focus on overall health and maximizing energy levels, instead of over emphasizing the numbers on the scale or calories in foods. Remember, young teens are growing and gaining height, which requires an increase in body weight.

Helpful Hints:


  • It’s okay to encourage your teen to finish their meal or snack, but do not force them to eat or to clean their plate. Prepare meals with high energy/calorie-dense foods and keep the volume of food normal or increase slowly.
  • It’s a great idea to offer a second helping of any food that your teen enjoys. For example, if they loves mashed potatoes, offer an extra scoop. If they are super thirsty at lunch, it’s fine for them to have another glass of juice, whole milk, or lemonade. If they are particularly hungry after school, give them an extra snack or double the snack portion. Take advantage of time of day when your teen’s appetite is best.
  • Eating on a schedule can help. Encourage your teen to eat three meals each day and three snacks in the mid-morning, afternoon, and evening before bedtime. This can help realign their hunger cues if they have been diminished.
  • Make an appointment with a dietitian who specializes in working with teens. The nutritionist will make an individualized plan for your teen with consideration for the eating habits of other family members. Your teen will learn specific ways to get the nutrition they need to reach a healthier weight.
Be sure that food and nutrition doesn’t take up all your time and thoughts or become the main focus of time spent together. Thinking and talking about nutrition are key when trying to encourage weight gain, but remember to have discussions about school, sports, current events, and feelings with your teen, too.