When your girl is gaining weight, it can cause you to worry. Learn why puberty weight gain happens and understand the most common reasons a girl gains weight.

As the mom of four kids (three of which are girls) who have moved through early puberty and the teen growth spurt, I’ve had firsthand experience with growing teenage girls, the onset of puberty, and weight gain.

As a health care provider and in my practice as a pediatric nutritionist, teen girls (and their parents) often show up with concerns about their daughter’s size.

In this article, I highlight what to expect with pubertal weight gain, and the most common reasons girls may experience body shape changes and extra weight gain during this time.

If your doctor has informed you of a body mass index (BMI) increase or an unhealthy weight gain, you may be looking for a medical reason as the culprit, such as low thyroid (hypothyroidism). In my experience, this is uncommon. 

Even so, most pediatricians and other healthcare providers will want to rule out a medical basis for any rapid weight gain they see, especially if growth patterns have changed considerably, or there has been a diagnosis of “childhood obesity.”

More often than not, though, a weight increase before and during puberty is related to a pre-teen’s stage of development, lifestyle, and/or daily food and eating habits. Extra weight gain may be caused by eating patterns and lifestyle habits, which I will review below.

Normal Growth versus Rapid Weight Gain

First, let’s clear something up. Weight gain is supposed to happen in growing girls. Earlier puberty may cause weight gain sooner than expected. When a girl gains weight, it’s likely a sign of normal growth and development. In other words, it may be perfectly normal and considered part of healthy growth.

If you look at the growth chart, you’ll notice a surge in the weight and height curves around the time of puberty and adolescence. This reflects the normal uptick in weight gain and height (or linear) growth. Until weight gets distributed and situated, the whole situation can look and feel awkward, especially for your child.

Some pre-teens will gain excess weight during this time, and too rapidly for their metabolic health. According to the Centers for Disease Control (CDC), 21% of 12- to 19 -year old females carry too much body fat.

Extra, unhealthy weight is associated with high blood pressure, high cholesterol, pre-diabetes, orthopedic problems, and more. As a parent who may be worried about your girl, your first job is to do a reality check: Is this normal growth, which you will see on the growth chart, or is this problematic?

Why is My Daughter Gaining Weight?

In addition to expected growth and the changes that come with it, like pubic hair and breast development, let’s look at some of the possible reasons a girl’s body changes may be concerning.

1. A Normal Growth Spurt 

The female body morphs quite a bit during the pre-teen and teen years. Did you know during the growth spurt, boys put on more muscle, while girls gain more fat? Girls get more curvy (and boys get more muscular).

The timing of puberty is around 10 to 12 years for girls. This is when they begin to see a lot of physical changes. The first period starts, on average, at 12 ½ years.

Most girls have completed the majority of their growing phase by age 14 or 15 years of age, but this depends on the start of menstruation. Girls who are late bloomers (who have delayed puberty) will start their growth spurt later and finish it later.

Weight gain is normal at peak growth times like puberty and should not be a cause for worry. If your daughter is experiencing normal growth, be as supportive as possible by focusing on my 7 strategies to support a teenage growth spurt. 

2. Poor Food Choices

In my own experience as a mom of daughters, I’ve witnessed how nutritious foods and healthy habits can get off track. Especially during the pre-teen and teenage years.

Pre-teens tend to socialize around food, as do teens. If your teen is driving, this adds another challenge to the situation. Teens who can drive often find themselves heading out the door to social events that involve food.

“I’m heading to meet my friends for coffee!”
 “We’re meeting for ice cream.”
 “I’m getting dinner with my friend…”

As a result, food choices may not be as nutritious as they can be.

For example…

• Sugary drinks such as soda or flavored coffee drinks that pack a lot of calories, fat and sugar (not to mention caffeine).
• Sweets and treats like candy and ice cream.
• Fatty foods (aka, “junk foods“) such as pizza, French fries and chips.

Having too many unhealthy foods in the diet disrupts the overall food balance and may contribute to weight changes. Of course, some of these foods are perfectly fine in the diet, and can be quite enjoyable. It’s all about the overall balance.

3. Poor Eating Habits

Many of our eating habits are formed in the early years. That’s why I’m a stickler about using an eating schedule with regular meals and establishing boundaries with feeding kids.

[If you want to know the secret to success, it relies on using a diplomatic feeding style.]

As a result of increasing independence, I often see females change their eating habits. They want more agency over their lives and this can include decision-making around eating.

They may:

• Skip breakfast
• Eat a light lunch
• Raid the pantry or refrigerator after school
• Eat late at night
• Use crash diets to lose weight

If these tendencies become habitual eating patterns, they can contribute to a poor diet and extra weight gain (or concerning weight loss).

4. Less Physical Activity

Teen girls are generally getting less physical activity than they were twenty or thirty years ago. I find it disheartening that schools nix regular physical activity around middle school. It’s a time when our girls need it the most to help them balance their health, wellness, and stress levels.

In high school, gym class is minimized to a few days a week, and actual exercise may be less than that. Recess, or a break to encourage physical movement? Nope.

While some girls play a regular sport and engage in training during the week, studies show that even athletes tend to sit around (quite a lot) when they’re not training, potentially minimizing some of the benefits of exercise.

Even if you have a daughter who is not inclined to move, she can be encouraged to be physically active. Muscle strengthening to build more muscle, gentle yoga, or a walk outside are ways to move the body for mental and physical health.

Exercise helps boost metabolism (aka calorie burning) and build muscle, both factors in maintaining a healthy weight, good body image, and optimal body functions.

5. Smart Phones and Computers 

Did you know that 20% of US teens spend 5 or more hours a day on their screens (computer, smartphone, tablet, and video games)? Social media and screen time are contributing to a sedentary lifestyle.

One 2016 study found that teens who spent 5 or more hours using smartphones and computers were twice as likely to drink more sugary drinks and less likely to exercise. Too much screen time may contribute to significant weight gain.

6. Lack of Sleep 

Does your daughter stay up later and have a hard time getting up in the morning? During the teen years, the circadian rhythm shifts. This means all teenagers get tired later than they did when they were younger. As a result, they go to bed later.

Yet, due to early school start times, they may need to rise early. This shortens their total sleep time, which may affect their ability to regulate their appetite and eating. Additionally, higher concentrations of growth hormone levels are released while sleeping, so getting enough rest is key to growing optimally.

A 2016 study showed that inadequate sleep, poor sleep quality, and late bedtimes were associated with extra food intake, poor food choices, and weight gain in adolescents.

All teens function at their best when they get at least 8-10 hours of sleep each night. Obviously, getting enough sleep along with daily exercise and a healthy diet is the key to a healthy, growing daughter. Sleep is not a waste of time!

7. Weight Training 

Strength training and the muscle mass gains that come along with it means that an overall uptick in weight can occur. Muscle weighs more than fat (or adipose tissue), so it’s a healthy weight gain, not one that comes with an increased risk of medical conditions.

8. Mental Health Challenges

More and more, girls from preteen to teen are experiencing more mental health challenges. An anxious or depressed state may contribute to emotional eating or overeating, and is a risk factor for eating disorders.

9. Eating Disorder or Dysfunctional Eating Behaviors

Some girls gain weight because they have dysfunctional eating behaviors like sneak eating, or an eating disorder like binge eating disorder.  Be on the lookout for changes in eating patterns, behaviors, or attitudes about food. 

Resources

• Check out our workshops, classes and guidebooks to help you nourish your teen, inside and out.
• Kids Thrive at Every Size: How to Nourish Your Big, Small, or In-Between Child for a Lifetime of Health and Happiness
• Teen Gaining Weight? 10 Sneaky Reasons for Teen Weight Gain