Growth Spurts!

Summary

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Brains On! – Growth Spurts!

Podcast: Brains On! Science podcast for kids
Host: Molly Bloom
Co-host: Andrea (from Piscataway, New Jersey)
Guest Voices: Jillian (Eugene, Oregon), Louis, and Gavin
Date: May 26, 2026

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Episode Overview

This engaging episode of Brains On!—part of a special Puberty series—dives into the science and real-life experiences behind growth spurts during puberty. Guided by host Molly Bloom and her youthful co-host Andrea, the show answers listeners’ questions about why and how kids' bodies change, why everyone grows at different rates, what “growing pains” actually are, and what’s really going on with stretch marks, sleep, and changing voices.

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Main Discussion Points

Meet the Hosts – Sharing Science and Stories

• [00:46–02:24] Molly introduces Andrea and chats about her love of acting, science raps, and press-on nail art—highlighting how science and creativity often mix in personal interests.

"There is a cell. It's the building block of life.
Then you step inside and you see the cytoplasm.
It's a jelly-like substance keeping afloat
all of the little organelle boats."
—Andrea rapping about cells (01:43)

Why Bodies Grow and Change

What is a Growth Spurt?

• [02:46–05:31] During puberty, kids experience not only visible changes (getting taller, heavier, longer arms and legs) but also internal changes, all controlled by hormones.
• Hosts stress that everyone’s growth timeline is different—being an early or late bloomer is normal.

"When it comes to puberty, there is no one normal...”
—Molly Bloom citing expert Karen Adderson (04:38)

The Role of Hormones

• [03:00–05:27]
  • Hormones = body’s chemical messengers guiding when and how we grow.
  • Sex hormones (testosterone, estrogen) and growth hormone (human growth hormone, HGH) are especially important during puberty.
  • HGH starts working in infancy (“up to 10 inches in their first year. That's like the length of a pineapple.” – Molly Bloom, 05:41).

Individual Experiences with Growing

• [03:46–04:13] Andrea shares feeling left behind as a late bloomer, echoing common worries (nothing is wrong, everyone’s timeline is unique).
• [04:13–04:46] Molly talks about getting "pretty pudgy" before her own growth spurt—pre-growth weight gain is normal.

Exploring Growth Spurts and "Growing Pains"

• [05:47–07:10]
  • Growth slows after toddlerhood but surges during puberty.
  • Growth spurts can be rapid (noticeable) or slow (barely felt).
  • Doctors now believe "growing pains" aren’t caused by actual growth but from being active (leg cramps at night).

Practical Challenges of Growth

• [07:12–07:41]
  • Outgrowing clothes, tripping over newly long limbs, feeling sleepy—common parts of growing.
  • “Your pants aren't getting shorter, your legs are getting longer." —Molly Bloom (07:34)
  • Feeling clumsy is normal; body parts grow at their own pace.

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Special Segment: Real Stories About Stretch Marks

[07:48–10:02] Jillian’s Stretch Marks Story

• Jillian describes sudden stretch marks as a tall, athletic middle-schooler, and her anxiety before learning they were normal.
• Learns from her mom (and shares with listeners): stretch marks can appear in various forms and colors, are not a problem, and happen to many people.

“I promise you will survive.”
—Jillian (10:01)

Andrea & Molly on Stretch Marks:

• Andrea: Her sisters and mom have them; “it’s part of your body changing shape.” (10:04)
• Molly: Likes to think of stretch marks as “tiger stripes; I think they're really cool.” (10:16)

Hunger and Sleep Needs During Growth

• [10:33–11:05]
  • Puberty increases hunger; bodies need more food for building new tissue.
  • Growth also happens during sleep—teens need more sleep.
  • “It's normal to feel like you could eat all the food in the fridge...” —Andrea (10:40)

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Science Spotlight: Circadian Rhythm

[11:05–12:02]

• "Circadian rhythm" is the body’s internal clock, directing when you feel tired or alert.
• Controlled by sunlight and, again, hormones.
• During puberty, circadian rhythm shifts: teens feel sleepy later but still need more sleep—making early mornings rough.
• “They're not being lazy. It's thanks to changes in their circadian rhythm.” —Expert Narrator (11:49)

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Why Voices Change: The Science of Sound

[13:44–15:45]

• Puberty's sex hormones trigger changes in the larynx (voice box) and vocal cords, making voices deeper.
• The process is just like tuning a guitar: thicker strings (or vocal cords) make deeper sounds.
• Voice “cracking” is normal as the body adjusts.

Personal Stories

• Louis: Voice changed unexpectedly; singing voice dropped from falsetto to bass, “allowed me to broaden my horizons.” (15:50)
• Gavin: Voice got hoarse in 6th grade; mom thought he was sick! Now comfortable with his new voice. (16:30)

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Key Insights & Memorable Quotes

• “When it comes to puberty, there is no one normal.” —Molly Bloom (04:38)
• "It's a good reminder that people grow at different rates and come in all different shapes and sizes." —Andrea (10:24)
• “Your pants aren't getting shorter, your legs are getting longer.” —Molly Bloom (07:34)
• “Stretch marks... just part of how my body works.” —Jillian (09:43)
• “Circadian rhythm. Circadian rhythm, Circadian rhythm.” —Andrea, showing off the science word of the day (12:02)
• “It's a journey. This is just part of it.” —Molly Bloom on puberty and growing up (17:21)

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Timestamps for Important Segments

• 00:46–02:24: Meet Andrea and her science raps
• 02:46–05:27: What is a growth spurt? What do hormones do?
• 07:48–10:02: Jillian’s story about stretch marks
• 11:05–12:02: Science word: Circadian rhythm
• 13:44–15:45: Why voices change and personal testimonials

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Episode Tone & Takeaways

Friendly, supportive, and science-packed, the episode reassures listeners that everyone’s development is different, answers common worries about puberty, and celebrates the fascinating, sometimes funny, sometimes awkward journey of growing up. Through stories, metaphors, and relatable examples, Molly, Andrea, and their guests help kids feel informed and confident as they experience their own changes.

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Curious about more puberty questions?
The hosts encourage listeners to send queries to their website for future bonus episodes.

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This summary skips show promotions, sponsor segments, and the episode outro.

Transcript

[Molly Bloom]

Lemonade. If you're looking for answers to all of your kids questions about puberty, just find our new show, Brains on Universe Presents Puberty, the podcast. Designed for kids age 7 to 12, the show answers their questions in a straightforward and digestible way. The podcast is hosted by me, Molly Bloom of the award winning science podcast Brains on and co hosted by high schoolers who've just been through it. Experts are on hand to provide science filled explanation explanations. Search for Brains on Universe Presents Puberty

[Andrea]

the podcast Brains on Universe. You're listening to Brains on. Where we're serious about being curious.

[Molly Bloom]

You're listening to Brains, part of the Brains on Universe. I'm your host Molly Bloom and my co host today is Andrea from Piscataway, New Jersey. Andrea loves to act, writes raps about science, and loves making press on nail sets. Hi Andrea.

[Andrea]

Hello.

[Molly Bloom]

So Andrea, tell me about some of the favorite roles you've had when you've been doing theater.

[Andrea]

My first ever musical role, it was SpongeBob the musical and I was Karen the computer. And I loved it because I was in a shiny silver outfit and I got to beatbox.

[Molly Bloom]

Oh my gosh.

[Andrea]

Yes, well.

[Molly Bloom]

And that goes right with your rapping.

[Andrea]

Yes.

[Molly Bloom]

So, okay, so you say you rap about science.

[Andrea]

Mm.

[Molly Bloom]

Tell me.

[Andrea]

Well, it started when my older sister needed help learning the periodic table and then she needed help learning the organelles and the cells. And I feel like I was always funny sibling. So this was just another way for me to help a sister out.

[Molly Bloom]

That's so cool. Do you have any of the wraps you could do for us off the top of your head?

[Andrea]

There is a cell. It's the building block of life. Then you step inside and you see the cytoplasm. It's a jelly like substance keeping afloat all of the little organelle boats.

[Molly Bloom]

Oh my gosh, I love that. Also press on. Nails. I know you have some amazing nails today. Yes, I spotted them. Are you always changing your nails up?

[Andrea]

I we have two other sets lined up. I like to match them if I have an event to go to. Like I had this Filipino cultural event, so I matched them to my outfit. And I also tend to wear a lot of black and dark clothing. So this is just a way to add a pop of color while also adding art to my outfit.

[Molly Bloom]

Very, very cool. Today we're sharing with you part of an episode from our new special series, Brains on Universe Puberty. The podcast, the full episode and much more are in a separate feed. Subscribe there to the whole series. This is an excerpt Covering stuff that anyone of any age might be interested in. This week we're talking growth spurts.

[Andrea]

During puberty, a kid's body goes through changes to look and sound more like an adult body.

[Molly Bloom]

Most kids will get taller. Your arms and legs might get longer,

[Andrea]

and you'll likely get heavier.

[Molly Bloom]

Bodies start growing and changing in other ways during puberty, too.

[Andrea]

Most of these changes happen to everyone, but how much they happen depends on your hormones.

[Molly Bloom]

Hormones are chemical messengers that travel around your body and tell different parts what to do. There are all kinds of hormones in our bodies all the time. Telling us when to sleep, controlling our blood sugar, helping us take action in

[Andrea]

stressful situations, and telling our bodies to grow.

[Molly Bloom]

We'll talk a little later in the episode about the changes these different hormones cause. First, we've gotten a lot of questions from listeners about how bodies grow in this stage of life.

[Andrea]

Why do we have growth spurts? What are growing pains and why do we get them?

[Molly Bloom]

Thanks for sending in your questions. So, Andrea, what was this growing part of puberty like for you? Can you remember?

[Andrea]

Yes, I remember that everyone started to get taller around fifth grade and get a little heavier around fifth grade. Their body was developing more and mine was not at all. Honestly, I was a late bloomer and so I felt like a little bit behind the bunch. I felt like there might be something a little bit wrong, but I don't know, I was a little stressed out about it as a kid.

[Molly Bloom]

But it turned out you were just a little bit slower at growing than the other kids. But it was still normal for you?

[Andrea]

Yes.

[Molly Bloom]

Yeah, I was always the shortest in my class. Even after I grew, like I was still the shortest. And right before I grew, I got like pretty pudgy. Like I got a lot of extra fat around my belly and stuff because my body was getting ready to grow and change. And I was a little self conscious about it before I knew what was happening. But it was normal. Just happens to a lot of kids. Like our expert Karen Adderson told us in the first episode, when it comes to puberty, there is no one normal. Some kids might grow really fast and others might take more time.

[Andrea]

All experiences are valid because there's no

[Expert or Narrator]

one normal and no one normal.

[Molly Bloom]

So during puberty you can expect to grow quite a bit. And again, all of this is thanks to our chemical messenger friends. Hormones.

[Andrea]

It's hormones.

[Molly Bloom]

So which of these hormones tell our bodies to grow?

[Andrea]

The sex hormones do, like testosterone and estrogen. And another important growth hormone that everyone has is called human growth hormone.

[Molly Bloom]

A pretty good name, if you ask me.

[Andrea]

As you might have guessed, its biggest job is to tell your body to grow.

[Molly Bloom]

And it's not just important during puberty. It starts being important from the very beginning, when you're just a baby. Babies usually grow a lot, up to 10 inches in their first year. That's like the length of a pineapple.

[Andrea]

Plus, babies often grow hair on their heads for the first time. They have teeth burst out of their gums. They lose baby fat and get stronger muscles as they become toddlers. It's a lot when you think about

[Molly Bloom]

it, but after a while, growth slows way down. After age 2 or 3, a kid might only grow a couple inches a year.

[Andrea]

But even though a kid's body might not be growing as fast, they are still changing a lot. It's just that most of that change is happening in the brain, so you can't see it.

[Molly Bloom]

We covered this in a brainzone episode called why Do Our Bodies Take so Long to Grow? If you want to listen, we've put a link on our website and in the episode description. For most kids, physical growth starts speeding back up during puberty.

[Andrea]

Human growth hormones start surging alongside the sex hormones and estrogen and testosterone.

[Molly Bloom]

And these surges make you get taller and gain weight.

[Andrea]

For some kids, this happens so slowly, they barely notice.

[Molly Bloom]

For others, it happens fast. That's called a growth spurt. For a long time, doctors thought some kids could physically feel their growth spurts in the form of growing pains. These were thought to be pains in the legs that feel like cramps.

[Andrea]

But doctors know now that growth doesn't actually cause pain.

[Molly Bloom]

They think the leg pains kids feel are actually related to being active during the day, since most kids feel them at night. But whatever causes these cramps, they can be annoying.

[Andrea]

And growing can be tough in other ways.

[Jillian]

Psst.

[Andrea]

Hand me the scissors.

[Molly Bloom]

It might seem like little elves are sneaking into your closet and cutting off the bottoms of your pant legs or shirt sleeves.

[Andrea]

Or tripping you out of nowhere. Uh oh, watch your step.

[Molly Bloom]

Or sprinkling sleeping sand onto your head during math class.

[Andrea]

But all of this is totally normal.

[Molly Bloom]

Your pants aren't getting shorter, your legs are getting longer.

[Andrea]

And getting used to that extra height means you might feel a little clumsy.

[Molly Bloom]

And as all of this is happening, some parts may be growing more than others, which, again, is totally normal.

[Andrea]

Jillian from Eugene, Oregon, shared a bit about her own experience with getting bigger during puberty.

[Jillian]

In sixth grade, I was like 11 years old, 5 foot 8 inches. Now I'm not so tall because everyone else Caught up. But in middle school, I was very tall and I started playing volleyball. I was working out hard and I was eating a lot because I was so exhausted. And so I was gaining a lot of muscle. I was gaining a lot of weight. And just when you hit puberty, like, you're going to gain weight and you're going to gain fat. One day I started to notice, like, these marks on my thighs. And I was like, oh, my goodness. Like, what are these? And I came across some sort of article talking about stretch marks. And I was like, oh, cool. Like, I think I have those. But in all the pictures, all the stretch marks were just like a really light version of your skin tone. And mine were not. Mine were purple. So I was like, oh, my goodness, I don't have stretch marks. I'm dying. And so at 11 years old, every night I went to bed and I was like, I'm not gonna wake up tomorrow. And then one day I really was like, I'm too young to die. I'm really into volleyball right now. Like, I wanna make it to our regional tournament, all this stuff. So I went to my mom and I said, mom, I'm dying. And I was very lucky. And my mom did not laugh at me. She said, jillian, why do you think you're dying? I said, look at these marks. And I showed her my stretched marks. And I was like, mom, like, they're non stretch marks because this isn't the color of stretch marks. She said, jillian, those are stretch marks. And I said, that's great news. I'm not dying. And that's really the best thing I could hear. And so now, as I've gotten older, I thought, like, that initial batch of stretch marks were just gonna be the only ones that I ever got. That was wrong. I get them all over my legs mostly, and a little bit up higher on my hips. And I know a bunch of people who get them all at different places. And so I just have stretch marks all where it's just part of how my body works. My body just grows and gets stretch marks. And mine are purple, which if you look it up on the Internet, they probably will not be purple. So you might think you're dying, but I promise you will survive.

[Molly Bloom]

Do you have stretch marks, Andrea?

[Andrea]

I do not, but my sisters have it. My mom has, of course, after being pregnant. And at first, as a kid, I was very confused on what they were, but now I just know that it's part of your body changing shape.

[Molly Bloom]

I know. I think they're kind of cool. I Don't really have them either because I guess I grew pretty slow. But I think they look like tiger stripes. I think they're really cool.

[Andrea]

Yeah. It's a good reminder that people grow at different rates and come in all different shapes and sizes. So it makes sense that people going through puberty have wonderfully different experiences, too.

[Molly Bloom]

All that growth during puberty takes a lot of energy, which means you might need more sleep than before.

[Andrea]

And like Jillian said, you will also need more fuel. During puberty. It's normal to feel like you could eat all the food in the fridge. Your body needs that stuff to build more body.

[Molly Bloom]

Exactly. And we do a lot of growing while we sleep. That's another reason many teens need more snooze time than before. Speaking of which, it's time for the word of the day.

[Expert or Narrator]

Today's word of the day is circadian rhythm.

[Gavin]

Circadian rhythm.

[Andrea]

Circadian rhythm. Circadian rhythm.

[Expert or Narrator]

The circadian rhythm is your internal clock that helps control your body's sleep wake cycle. It's not an actual clock. Your cells aren't wearing tiny wristwatches. They don't even have wrists. Instead, it's more like a pattern of when you feel awake and when you get sleepy. It's controlled by exposure to sunlight and, as always, hormones.

[Andrea]

Always with the hormones, is there anything they don't affect?

[Expert or Narrator]

Yes, yes, hormones do. A lot. So it makes sense that there's a natural shift in the circadian rhythm of teenagers. First of all, teens need more sleep than before to help with all that growing. They also tend to take longer to feel sleepy. That's why lots of teens stay up late in the evening and they have more trouble waking up and getting going in the morning. They're not being lazy. It's thanks to changes in their circadian rhythm.

[Andrea]

Circadian rhythm, Circadian rhythm, Circadian rhythm.

[Molly Bloom]

Word of God the Day Coming up why Voices Go low as We Grow Stick around. Do you have more questions about puberty? Send them to us because we're going to do a bonus episode of this series to answer your most burning questions. Is there a topic you want to know more about? Advice for body stuff or friend stuff? Get in touch. Send your questions to brainson.org contact and you might hear an expert answer them. That's brainson.org contact Thanks. Today's episode is sponsored by Great Wolf Lodge. At Great Wolf Lodge, there's adventure for the whole family. You and your pack can splash away in the indoor water park where it's always 84 degrees. There's a massive wave pool a lazy river and tons of water slides for your pack to enjoy together. And the fun doesn't stop there. Get ready to explore and play at Adventure Packed attractions from Magiquest, a live action game that takes place throughout the lodge, to the Northern Lights Arcade. There's also a bunch of great dining options and complimentary daily events like nightly dance parties, all under one roof. And the best part? With 22 lodges across the country, you're always only a short drive away from adventure. So bring your pack together at a lodge near you. Book your stay [e-mail] and strengthen the pack.

[Andrea]

This is Brains on Presents Puberty the Podcast. I'm Andrea.

[Molly Bloom]

And I'm Molly. Before the break, we talked about a special chemical in the body called human growth hormone. This hormone causes growth to speed up for many kids during puberty.

[Andrea]

It's hormones. Now we're going to talk about another set of hormones. Sex hormones. Estrogen, progesterone, and testosterone.

[Molly Bloom]

We talked about these back in the first episode of the series with Dr. Kara Nattersen. And the hormones that are most involved with puberty are the sex hormones, namely estrogen and progesterone and testosterone. And every single person has all of these sex hormones.

[Andrea]

During puberty, your body produces a lot of these hormones, which kickstarts the changes that make your body look less like a kid's and more like an adult's.

[Molly Bloom]

One change you won't see but will probably hear is in your voice. During puberty, our voices get deeper, more like an adult voice.

[Andrea]

All kids voices change during puberty, usually between the ages of 10 and 16.

[Molly Bloom]

This change happens because your larynx, also known as your voice box, is growing.

[Andrea]

The larynx is a small hollow tube in your throat that controls the sound of your voice.

[Molly Bloom]

Stretched across your larynx are your vocal cords. They're like two elastic bands. And as your larynx grows, your vocal cords also grow, getting longer and thicker.

[Andrea]

Think of a guitar. The thinner strings sound like this

[Molly Bloom]

and the thicker strings sound like this.

[Andrea]

Hear how the thicker strings sound much deeper? It's the same with your voice.

[Molly Bloom]

As your voice is changing, you might notice that it's sometimes difficult to control. It might squeak. Sometimes people describe it as cracking or breaking, which can be annoying or awkward.

[Andrea]

But this is totally normal and it's just your body getting used to the change, right?

[Molly Bloom]

Imagine that same guitar getting tuned.

[Andrea]

Eventually it'll even out.

[Molly Bloom]

Louis and Gavin shared a bit about their own experiences with voice changes.

[Louis]

I totally remember when my voice first changed. I used to be a super, super big singer. In middle school, I had a falsetto like no man's business. And then one day I just started, like, slowly realizing that my voice could not go as high or it started to crack. And I was like, wait, what's going on? This makes no sense. I didn't know it was gonna affect my singing voice. And then my falsetto went into a bass and I was singing much, much, much lower, which was a little startling to. But I knew that it allowed me to broaden my horizons and try something completely new, which is really awesome. And I loved to sing lower and did it all throughout high school.

[Gavin]

My voice started to change a little around sixth grade, and it was really funny. For a while, my mom just thought I was sick and I had a hoarse voice. So she kept saying, like, oh, do you need, like, tea or like some, like something warm because your voice sounds kind of hoarse. And I was like, oh, I guess maybe I do. But then it kind of settled in to stay. And I do remember a few times having voice cracks. Still does happen now. And I remember, yeah, kind of being embarrassed. But honestly, it's just a part of life. And I feel pretty happy with how my voice sounds, actually.

[Andrea]

Remember, puberty is a period of intense growth. But it's not the only change your body has been through or will go through. It will keep changing your whole life.

[Molly Bloom]

It's a journey. This is just part of it. During puberty, your body goes through changes to look and sound more like an adult's.

[Andrea]

Most kids will get taller and heavier and their voices will change. These changes take place because of hormones.

[Molly Bloom]

That's it for this episode. And this is the last excerpt from the Puberty series that we'll be sharing here on brainson. If you want to hear the rest of the series, search for BrainZN universe presentation Puberty the Podcast and subscribe. We're releasing new episodes every Friday for the next six weeks. We have episodes coming up about mood swings, friendship changes, crushes, periods, reproduction, and more. Again, just search for Brainzon Universe presents Puberty the Podcast. Now it's time for the Brains Honor Roll. These are the incredible kids who keep this show going with their questions, ideas, mystery, sounds, drawings and high fives. Abigail from Longmeadow, Massachusetts. Owen from Timonium, Mary. Jocelyn from St. Paul, Minnesota Millie from Portland, Tennessee. PJ and Louis from Evanston, Illinois. Finnegan from Woodbury, Minnesota. Sean from Bangkok. Brooks from Round Rock, Texas. Violet from Klein, Texas. Charlotte from Bear, Delaware. Henry from Lake Bluff, Illinois. Nikki from Tallahassee, Florida Dante from London, England Phoebe and Deacon from Austin, Texas Olive from Vancouver, Washington Vera from Baltimore, Maryland Amitas from State College, Pennsylvania Marin from Sonoma, California Kian from Toronto Guillaume from Portland, Oregon FIA from Lakefield, Ontario Pepper from Maple Grove, Minnesota Atticus from Staten Island, New York Maude and Francis from Portland, Oregon Danadu from Hillsboro, Oregon Ezra from Singapore Leo from Ascot, uk Sasha from Abu Dhabi Elliot from Apex, North Carolina Finley from Portland, Oregon Aiden and Rowan from Kent, Washington Phoenix from Davis, California Annie Vay from Redondo Beach, California Caden from Vancouver, Washington Jabin from Seattle Thomas from Pittsburgh Samuel from Honolulu Matthew from Bowie, Maryland Oliver and Violet from Vandalia, Ohio Bowie from Glendale, California Cora and Joel from White Salmon, Washington Fiona and Sylvia from Bar Harbor, Maine Leak from Halifax, Nova Scotia Leora from Berlin Arlo from Toronto Octavia from Phoenix, Arizona Emmy from Houston, Texas Margo from Orinda, California Ezra from Los Angeles Adelaide from Fort Smith, Canada Rubesh from Starkville, Mississippi Ella from Oxford, uk Dylan from Taipei, Taiwan Dax from Portland, Oregon Louisa from Decatur, Georgia Penn and Amelia from Lakewood, Ohio Howell from Fairbanks, Alaska Mateo from New York City Robin from Berlin Ella from Chicago Augie from Sussex, Wisconsin Stella from Ali, Oregon Jack from Scarsdale, New York and Livingston and Elwin from Durham, North Carolina. We'll be back next week with an episode featuring everyone's favorite monster, Gungador.

[Andrea]

Thanks for listening.