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Why the School Day Should Start Later: Sleep and Obesity

By Heather Turgeon |

I remember the feeling of having to peel myself out of bed as a child–the crack of dawn, cold…even dark outside while I prepped for school. We know that adolescents naturally start to stay awake later at night (their circadian rhythms tell them to do it). Add in texting and other late night distractions and you’ve got a true night-owl on your hands.

We hear a lot about how drowsiness affects a kid’s academics and mood. But what doesn’t get enough air time is that sleep is strongly tied to weight gain too.

A study released this week in the journal Sleep reports that teens who don’t sleep enough are more likely to eat fatty foods than their well-rested peers. Sleep-deprived adolescents consumed 2.2 percent more calories from fat, and for each hour subtracted from nighttime sleep, a teen is 21 percent more likely to consume a high number of calories from snacks.

Consider how the bump in calories adds up daily–the researchers think the tweaks to a person’s diet cause weight gain and contribute to the rising incidence of obesity in this country.

It’s not a new concept, as readers of Nurture Shock will remember, that the “lost hour” of sleep is linked to weight gain. So why do fewer nighttime zzz’s add up to snacking and fatty foods?  And how much sleep do our kids need to avoid this problem?

The teens in the study who sleep fewer than eight hours were the ones who packed in the calories. The American Academy of Sleep Medicine says teens need at least nine hours of sleep per night. (Children ages 5 to 12 need at least 10, three to five-year-olds need at least 11, and one and two-year-olds need at least 12.5, including naps).

Disrupting sleep sends the body’s biological clock out of whack, which trips off a whole cascade of altered hormones that influence mood and appetite. The short story–a donut is more likely to end up in your hands. I (and some of my fellow bloggers are with me here) can attest to this phenomenon.

And I wouldn’t be surprised if even my two-year-old falls victim to this pattern–I’ll be watching his sleep and his tendency to ask for just one more serving of “ice tweam.”

Image: Everystockphoto/Brianfit

More from Heather Turgeon:

Antipsychotic Medications for Toddlers?

The Bed Bug Mystery: Why They’re Clean and Why They’re Back.

Worried About Dad: Study Says Men With Trouble Sleeping Four Times as Likely to Die.

C-Section Twice as Likely When Doctors Induce Labor.

Why I Abandoned the “Readiness” Approach to Potty Training.

Are Babies Sleeping Less These Days?  5 Nap Tips and More.

Judge’s Ruling Blocks Stem Cell Work.  Is it Even More Restricted Than Under Bush?

Dad’s and Babies Re-Wire One Another’s Brains.  So What if He’s Not Around?

Circumcision Rates in the U.S. Falling Fast.

More on Babble

About Heather Turgeon


Heather Turgeon

Heather Turgeon is currently writing the book The Happy Sleeper (Penguin, 2014). She's a therapist-turned-writer who authors the Science of Kids column for Babble. A northeasterner at heart, Heather lives in Los Angeles with her husband and two little ones. Read bio and latest posts → Read Heather's latest posts →

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8 thoughts on “Why the School Day Should Start Later: Sleep and Obesity

  1. goddess says:

    So when do you propose starting the school day? Our elementary schools run 9am -3pm. Busing can take up to 45 minutes. Add in homework. When is dinner supposed to occur? We eat at 5pm- and I will NOT have it later than 5:30 due to various members of the family’s reflux issues at night.
    And- while you have a minor child, why tolerate them staying up all night anyway?
    Tail waggin’ the dog WAAAAY too much in this country. Do this and this generation will be telling their employers when THEY are available to start working each day, LOL. See how well THAT goes over.

  2. goddess says:

    BTW- you can disconnect the land line phone and internet from the home at a certain hour at the point of entry- and confiscate cell phones and other electronic devices. Why do parents act so helpless with their teens??????????? Terminate the cell phones, block their PC IPs from your router. Geez….

  3. Laure68 says:

    I am doubtful that an early start to the school day is causing the obesity problem. In the “olden days” we also had to start school early and there were not as many obese kids.

  4. jenny tries too hard says:

    Your elementary school starts at 9am? Do you live in Heaven? My kids have a tardy bell at 7:40am and go til 2:40pm. Last year it was 8:05-3:05pm. Middle school starts at 8:20 I think and high school starts at 9 in my district. I could definitely stand a later start time, even if it did go til 3:30 or later.

  5. heatherturgeon says:

    Lots of researchers and educators are on the side of later start times, especially for high schoolers (some high schools start earlier than 7:30am). The combo of sleep deprivation and unhealthy snacks+lunches in school can’t be good. 9:00 am sounds like a dream! Here’s a recent la times article about the debate too

  6. Voice of Reason says:

    For those not lucky enought to have a copy of this gem on their book shelf, here’s a link to a summary of the sleep chapter of Nurture Shock:
    I’m all for the family hierarchy, but the problem of teen exhaustion is proven to be rooted in biology, not lack of disciplne.
    Sleep is an such important issue and I’m so pleased to see this article! Its connection to obesity is not only noted in Nurture Shock, but by the Center for Disease Control. From my point of view, this is a topic that needs more attention and more discussion.
    Thanks, Heather!

  7. goddess says:

    Flavor/cause du jour. I’m sure the next leading research will show that early risers are more successful in life.
    Guess I’m lucky my teen was able to keep the traditional family schedule with us.

  8. Simon says:

    Goddess: A few facts:

    20% of the population are night owls, 20% are early birds, and the remainder are in between. (In Seattle, that balance changes; 50% are night owls according to a study from a few years back).

    Teenagers naturally become night owls. It’s a hormonal, puberty-driven thing. Their brains work better on a later schedule. Let them get up later, and they function better, learn more and are generally happier. That doesn’t mean let them be lazy – that just means let them be the traditional typical human teenager, and let them get up on the body’s preprogrammed schedule.

    As for early risers being more successful? That’s most likely the same damn thing. Night owls being penalized because industry is designed around the needs of early birds.

    When I’m left to my own devices, my typical sleep cycle is from 5am to 12pm. I do my best work from 8pm to 12am. (I do this typically around this time every year; the holidays are a nice chance for me to switch back to /my/ schedule).

    When I do so, I’m 3x more productive. I’m less distractable. I’m focused, happy and way more creative. The ADD traits I have disappear, I don’t get morning brain fog, and I’m less stressed.

    And then the holidays end, and I go back to work on a “normal” schedule.

    I tell you… It’s a waste of money. And I’m happily successful, thanksmuch. I’ve directed companies, run teams of people, and right now I’m in the advanced tech group of a major company.

    What I don’t understand is why you would want to enforce your schedule on someone else, when obviously it doesn’t work for them. That, and why you show so much disdain for research which has been proven again and again.

    Try reading Outliers by Malcolm Gladwell – it’ll open your eyes.

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