Does Being Underweight Affect Puberty?


The teenage years are an essential time of growth and development. Your body has a lot going on and must be prepared to handle everything being thrown at it!

Being underweight can affect puberty- often by delaying it. Teens that are underweight are often either undereating or not absorbing nutrients from the food they are eating. This leads to a lack of nutrients and is not great for a developing body! Maintaining a healthy weight through eating plenty of nutrient dense foods and exercising appropriately is a good way to make sure puberty happens at the right time and the right rate. 

Read on for more information about how to know if a teen is underweight and how they can maintain a healthy weight.

Does Being Underweight Stunt Growth?

Remember that there is a difference between being small and being actually underweight. Every teenager’s body is different and will grow and develop at a different pace!

That being said, your body needs fuel to grow. Being underweight is often a symptom of not consuming enough energy. If you are consistently eating less than your body needs, your body won’t want to expend any energy to grow- it is more focused on keeping you alive!

If fuel is not available during this period of growth, it is possible that teens could not reach their full growing potential. 

There are other things that could cause a teenager to be underweight. Some medical conditions could be playing a large role. Those should be addressed as soon as possible by your doctor so that your child doesn’t miss out on growth opportunities!

Will Puberty be Delayed if Your Teen is Underweight?

Puberty is a huge part of growth and development at this stage in life. Puberty is all about the development of certain hormones and the signals they give other body parts to develop.

Just like with overall growth of your body, you need adequate energy and nutrients to begin puberty.

Everyone hits puberty at a different time, so it is not a good idea to compare your teen with other people their age. Don’t make your teenager feel like something is wrong with them just because their growth and development is happening at a different pace than those around them!

Regularly meet with your child’s doctor to make sure they are healthy and developing at a pace that is appropriate for them!

Is it Bad to be Underweight as a Teen?

Let me be sure to clarify here- if your teen is underweight, it does not mean they are bad. Referring to a teen’s weight as “good” or “bad” is not a great approach. Teens can easily misinterpret messages and therefore feel shame about themselves and their body. 

Still, being underweight can lead to negative health outcomes. Find a healthcare provider that puts more emphasis on healthy habits than just weight. If weight gain is necessary, work with a dietitian that makes your teen feel comfortable and confident in their own skin while working towards a healthier weight.

How Does a Teen Know if They are Underweight?

Technically, a teen is classified as underweight if they are below the 5th percentile on the Center for Disease Control’s (CDC) growth charts.These growth charts use Body Mass Index (BMI) to track weight trends as children and teenagers grow. It is much more valuable to look at weight trends than to base health status off a single 

BMI is not the only thing that should be looked at when determining weight status. Genetics, activity level, body composition, eating habits, stress levels, mental health status, and more should be considered when looking at weight and overall health status.

Even a teenager that is technically in the “normal weight” range could have problems with growth and development, so all factors should be taken into account when monitoring teens!

When to Be Concerned About Your Teen’s Weight

The best practice is to take your teen to see their doctor regularly to measure growth trends and make sure that everything is on track. If you or your teen are concerned about weight or development and onset of puberty, talk to a doctor about that too! 

Be aware that eating disorders are very prevalent in teenagers. Parents should look for signs of a poor relationship with food and body image and reach out for help from a qualified professional as soon as they notice that their teen is struggling! Here are some things you can look for!

  • Tracking everything that they eat
  • Going to the bathroom religiously after meals
  • Binging or purging
  • Eating in secret
  • Feeling nervous or anxious about eating certain foods
  • Going long periods of time without eating or eating very little
  • Hiding food
  • Pinching body fat or looking at their body in the mirror regularly
  • Excessive exercise for the purpose of burning calories
  • Skipping breakfast or other meals
  • Using caffeine for energy
  • Using laxatives, weight loss pills, enemas, etc.
  • Feeling bad or guilty about how much they ate
  • Eating so much food that they feel sick afterwards
  • Changes in weight
  • Irregular, loss of, or delayed start of menstrual cycle
  • Food restriction
  • Cutting out certain foods or food groups
  • Fear of “unhealthy” foods
  • Avoiding social situations that will have food
  • Dieting
  • Mood swings
  • Depression and anxiety
  • Stomach pain or constipation
  • Low heart rate or blood pressure 
  • Feeling cold
  • Headaches or dizziness
  • Food rituals or patterns of eating
  • Fear of eating different foods
  • Fear of eating out
  • Belief that life will get better once they are at a certain weight
  • Wearing clothes that hide their body shape
  • Feeling out of control with eating
  • Sore throat or swollen glands
  • Knuckles that are bruised or callused
  • Sunken eyes, bloodshot eyes, light bruising under eyes
  • Clinical labs outside of normal ranges
  • Perfectionist mindset
  • Obsession with health and wellness
  • Etc.

That list might look overwhelming and for good reason! Disordered eating, a poor relationship with food, and diagnosed eating disorders are very overwhelming and require professional help. Make sure your teen knows that they can talk to you if they are struggling with food or body image. Make your home a safe space where they can reach out for help!

Tips for Healthy Weight Gain for Underweight Teens

If your teen needs to gain weight, work with a dietitian to make sure their individual needs are being met. Here are some general tips for weight gain that teens can incorporate.

  1. Eat at least every few hours. If you are eating only 3 meals a day, it may be challenging to get enough food without feeling overly full.
  1. Keep snacks with you at all times! This is especially helpful for active teens or teens that are on-the-go frequently. 
  1. Include healthy fats with all meals and snacks. 
  1. Include more nuts and nut butters with meals and snacks.
  1. Add seeds to smoothies, cereal, oatmeal, yogurt, salads, etc.
  1. Top meals with cheese, or add cheese to sandwiches.
  1. Add avocado to smoothies (it adds a creamy texture), rice bowls, salads, sandwiches, soups, tacos, burritos, quesadillas, etc.
  1. Cook with olive oil. Add a generous amount during the cooking process or drizzle on top of pasta, veggies, rice, potatoes, etc.
  1. Olive oil can even be mixed into sauces like ketchup and barbeque sauce to increase calories.
  1. Drink calories! Carnation Instant Breakfast adds some extra protein to a glass of milk and pairs well with lots of yummy breakfast foods. 
  1. Smoothies are also a great way to get a lot of calories in a drink! Some potential ingredients are  greek yogurt, frozen fruit (bananas, peaches, pears, berries, etc.), spinach, avocado, peanut butter, almond butter, chia seeds, flax seeds, etc.
  1. Mix greek yogurt with peanut butter for a yummy high protein dip for apples, or bananas.

Summary

Being underweight as a teenager can definitely have effects on puberty and growth. Low energy intake, malabsorption, and low body fat can all mess with hormone levels, and result in nutrient deficiencies that could negatively affect growth and development. 

The growth of your teen should be carefully monitored by a doctor and weight and development concerns should be addressed before they get too serious. Parents and healthcare providers should also monitor teens for other medical conditions and eating disorders and get treatment as early as possible.

Weight and physical development can be tough for teenagers. Do not draw excessive attention to weight and be careful how it is discussed. Even making negative comments about your own body can convey unhelpful messages to teenagers that are in earshot. 

Help your teen create a positive relationship with their body, with food, and with overall health!

Resources

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

Wolfram T. Understanding Eating Disorders. Eatright.org. Published February 26, 2019.

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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