How to Gain Weight for Teenage Boys

There are a lot of pressures to look a certain way and have a certain body type. Some body types are glamorized in movies and on social media, and this can be hard for a teenager who doesn’t feel like their body “fits the mold.” Some teenagers that are underweight may benefit from gaining weight, while others might want to gain weight or build muscle for aesthetic reasons or for improved sports performance.

Although there are helpful tips for gaining weight and building muscle, remember that the pursuit should be done with help and support and should not come at the expense of a teenager’s mental health.

Weight gain for teenage boys should be gradual. Rather than just simply eating as many calories as possible, focus on still getting a balance of foods from all of the food groups so that your body has all the nutrients it needs to grow. Teenage boys that want to gain weight should eat regular, balanced meals and snacks throughout the day. Do not skip meals. Nutrient dense and energy dense foods like avocados and nuts are easy ways to bulk up calories without having to consume an enormous quantity of food.

Read on for more tips for gaining weight for teenage boys, information on who should gain weight, and specific tips for building muscle.

How to Tell if You Need to Gain Weight as a Teenager

Most doctors will track weight trends over time using Body Mass Index (BMI). BMI can be calculated using height and weight. By plotting these measurements on growth charts, doctors can classify if a child or teenager is underweight, normal weight, overweight, or obese. 

Generally, teenagers under the 5th percentile are considered underweight. However, using BMI as the only way of determining if someone is at a healthy weight is inappropriate.

Other factors should definitely be considered when determining if a teenager needs to gain weight. Your healthcare provider should collect information about eating and exercise habits as well as mental and emotional health.

Genetics and frame size play a huge role in a person’s weight. Some people are just smaller than others, and their weight might still be healthy for them. Similarly, other people with a larger frame size sit at a higher weight, but that might also be a healthy weight for them. This is why it is important to look at all the factors when determining if a teenager needs to gain weight.

There are some cases where there is more going on than just simply not eating enough. Thyroid issues, absorption issues, and other medical problems could actually be the root of a teenager’s low weight and should always be addressed if present. If improvements in dietary patterns do not change weight, this could also be a sign that something else is going on that needs to be addressed.

Other circumstances might lead to teenagers wanting to gain weight even if they are not technically considered “underweight.”. Athletes in particular often desire to bulk up and gain muscle to perform better or for aesthetic reasons. 

However, teenagers should be carefully monitored for unhealthy methods of weight gain and disordered eating. Your current weight or change of weight should not be damaging to your mental health!

If a teenager is wanting to change their weight, they should consult a doctor and dietitian to monitor the process and guide them along in a healthy way. Find a healthcare provider whose main focus is on overall health rather than weight alone!

What Foods Should You Eat to Gain Weight?

You might think that a quick way to gain weight is just to eat a bunch of high calorie foods like fast food and desserts.. While fast food and desserts are not off the table by any means, teenagers wanting to gain weight should still consume plenty of nutrient dense food to support their growing body. 

Teens wanting to gain weight should eat a good balance of carbohydrates, protein, and fat that are nutrient dense. Listed below are some examples of great food choices in each of those categories!


  • Whole wheat bread and pasta
  • Fruit, fresh, frozen, dried, and canned (in light syrup)
  • Hot cereals (oatmeal, cream of wheat, etc.)
  • Potatoes and sweet potatoes


  • Cheese
  • Milk
  • Yogurt
  • Hummus
  • Beans
  • Nut butters (peanut butter, almond butter, etc.)
  • Eggs
  • Lean meats (chicken and turkey)


  • Avocado
  • Nuts 
  • Seeds
  • Oils (olive oil and canola oil)

Tips for Healthy Weight Gain for Teenagers

If a teenager is wanting to lose weight here are a few things to think about:

  • It is helpful to understand how much energy your body is burning. In order to gain weight, teens must be eating more than what their body is expending. Your body will then be able to use excess calories to build muscle and store fat.
  • How quickly you should gain weight is also different person-to-person and depends on many factors. Some people will do better eating 100-300 calories higher than what they are burning, while others might need 500-1000 excess calories each day, or even more! Talk to a dietitian about what approach would be best for you.
  • Consistency is key. If you are overeating on some days and undereating on other days, you likely won’t see much progress. Instead, make a plan that is sustainable and that you can stick to!
  • See food as fuel and a way to take care of your body. As you eat more, you will be giving your body more nutrients to work with.
  • Remember that your body will adjust to eating more food, but it might be hard at first. You may need to start by adding in small amounts of food and increase the quantity as your body adjusts.
  • Calorie needs change every day. Some days you might need more than others if you are more active. A dietitian can help you make a plan that accounts for changes in energy needs day to day!
  • Eat consistently throughout the day. It will be much easier to eat enough food if you don’t save all of your calories for the end of the day. Your body will also have that energy available all day!

Tips for Increasing Calories

In order to make it easier to consume extra calories, it helps if the quantity of food you have to eat doesn’t seem gigantic. Healthy fats are especially helpful for increasing calories without increasing the quantity of food all that much. Here are a few tips and ideas for increasing calories!

  • Cook with olive oil. Drizzle oil on top of cooked vegetables, pasta, rice, or other foods!
  • Add a slice of cheese and part of an avocado to a ham sandwich
  • Add nuts to salads, and other dishes
  • Nuts and dried fruit are both energy dense and provide a balanced snack when eaten together
  • Mix olive oil into dips like ketchup or barbeque sauce
  • Power pack smoothies with nut butter, chia/flax/hemp seeds, 
  • Add sour cream, cheese, and avocado to soups and salads
  • Add granola, nuts, berries, and seeds to yogurt for a filling snack
  • Add nut butter, or flax seed to sauces and dips
  • Smoothies can even be bulked up with ice cream for a sweet treat 🙂

Getting calories from food is the best case scenario, but high calorie supplement drinks might be appropriate for a teenager that is really struggling to eat enough. Ask your doctor or dietitian if a supplement would be appropriate!

How Do Teenage Boys Build Muscle?

When trying to gain weight specifically through increasing muscle mass, there are a few things to take into consideration.

  1. Your body still needs a balance of carbohydrates, protein, and fat. While protein needs might be a little bit higher, if the body is not getting enough energy from carbohydrates and fat, it will be much harder for your body to build muscle.
  1. Protein intake should be spaced out throughout the day to better promote muscle growth. Aim to get around 20 grams of protein every 3-4 hours. Balance those meals and snacks with good sources of carbohydrates and fat.
  1. Don’t forget about the importance of muscle strengthening exercise! Weight training is a big part of gaining muscle. Teenagers should be careful to not start heavy lifting at too young of an age and they should seek guidance to ensure they weight train safely.
  1. Aim for a variety of protein sources. Whey protein (milk based protein) has been shown to be beneficial for athletes trying to build muscle. Milk is a great source of protein, carbohydrates, and nutrients like calcium that promote bone strength!
  1. Check with your doctor before using a protein supplement, and then make sure it has been tested by a third party and is safe for consumption. 


Weight gain takes consistency and a little bit of nutrition knowledge! Since teenagers are at such an important time of growth and development, seeking help from a dietitian when making changes to eating habits is always a good idea. A dietitian can help guide teenagers to increase calories in a healthy way while still developing healthy eating habits and establishing a healthy relationship with food.


Centers for Disease Control and Prevention. About Child and Teen BMI. Published March 17, 2021.

Serbinski K. Safe weight gain tips for underweight kids. Published August 28, 2018.

Katherine Harmer, RDN

I'm a Registered Dietitian Nutritionist with a love for coaching others to success in their health goals, especially teenage athletes. Tennis was my sport of choice in high school. Now I'm a little bit older, a little bit smarter, and a little bit worse at tennis.

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