The thoughts that were thunk and the goings on of my life.

Sunday, November 11, 2012

Calories Burned During Childbirth

During our birthing class the instructor said something that set off my truth-o-meter:
During childbirth you will burn about 50,000 calories

I thought it would be pretty easy to debunk this, but didn't want to harp on it during class and look like a jerk; however, there's no way it could be true, right?

So then an internet search found...
  • Rumor has it that you burn about 50,000 calories during the typical labor. -Chacha
  • aparently 50,000 - Baby Forums
  • On google it says up to 50,000 - Baby Expert
  • She said during her child birth classes she was told about 50,000...but like other people said it depends on each labor because every labor is different!” - Baby Forums
  • Up to 50,000 calories during the typical labor!
    and
    I just looked up the figure and the consensus seems to be with Invisible Pink RN. 50,000. - Yahoo Answers

...ok, so maybe this IS real? Time to put this theory to the test.

Can you burn 50,000 calories during labor?

Let's look at this from a few different angles: weight loss, heat dissipation, and maximum known calorie burn rates.

Weight Loss:
Q: How much weight would you lose if you burned that many calories?
A: Fat has about 3500 calories per pound. 

50,000 cal / 3500 calories per pound = 14.2857 lbs

Therefore if this stat is true, during a birth you'd lose over 14 and 1/4 lbs of fat!

Well shoot, that doesn't seem likely unless you count the baby and placenta as 'calories lost'. But then you'd have to burn the baby for the statement to hold true...and most hospitals don't allow infant sacrifice.

Heat Dissipation:
Q: Since burning calories ends up just creating heat, how hot would you get if you burned 50,000 calories during birth?
A: Let's look at one of the most intense physical activities there is, running a marathon. I'm not talking jogging, I'm talking actually running and hard. One of the real limiting factors when you're at your threshold is simply cooling yourself. Just look at times for warmer marathons; there definitely slower.

How many calories do you burn during a marathon?
Depends on the person, but looking at the top marathoner's time (2:03:38; we'll call it 2 hours), and how much they weight (about 125 for this more elite group), and combine it with a calorie calculator (this suggest about 2500 calories).

This means that they burn about 1250 cal/hr and weigh about 125lbs (~56kg). A calorie by definition is the amount of energy it takes to raise 1 kg of water 1 deg celsius. This means the marathoner is able to dissipate about 22 degrees worth of heat per hour.

So let's say that birth is a 16 hour process. 50,000 calories in that time equals 3,125 calories per hour. This is about 2.5x as many calories as a top-marathoner. It means you'd have to burn 55 degrees per hour; but since a marathoner is really cooling as much as humanly possilbe it means...

If you burn 50,000 calories during birth your body temperature is going to be 70 degrees celsius; which is 158 degrees Fahrenheit for you Americans.

...hmm, that doesn't seem very likely.

Maximum Known Calorie Burn Rates
What's the maximum calories a human can burn for any duration?

Here's a good list: http://www.nutristrategy.com/activitylist.htm
About the max you can burn is 1500 cal/hr...and even then only if you're cross-country skiing uphill and weight 205 lbs.


Conclusion
So I think we can very confidently say:
It is completely impossible for anybody to burn 50,000 calories during labor

But what is the answer?
Most women don't want to be hooked up to a set of lab equipment to accurately read the full metabolic effects of birthing; but it all depends on the labor. Some ladies can go start to finish smoothly in 2 hours, others have a sufferfest for over a day.

Sure in pain-per-hour birthing wins pretty much everything. You'll probably burn in the high-hundreds to a few thousand calories depending upon intensity and duration of the labor.

So why is the 50,000 number circulating? 
Simple it's a self-perpetuating myth. Most people heard it from their birth instructor, who double-checked it on the internet, where somebody was already saying what that instructor said. Once it got in a google search it became a self-fulfilling myth.

Bottom line:
Don't use birthing as an excuse to stuff 50,000 calories in your face...but if that's what your wife wants to do, don't tell her no in that moment either.

12 comments:

Marena said...

Love the last line!

Jewels said...

Great article!
I think when body is in pain it has a totally different scale of calorie burn rate. I agree that 50,000 it absurd. Who ever came up with this number... But having 3 children i can say that if you take away baby and water and placenta weight on average i lost about 5-6lb. So about (5x3500cal=17500cals)

Angela Hudler said...

Very interesting! I saw this too and googled it. Glad I found this blog first! It seemed too crazy to be true!

Angela Hudler said...

Very interesting! Thanks for doing the work to figure this out! I'm glad I found your blog first when I Googled. Seemed crazy and it was. :)

MollyNPaul MatterDixon said...

I would actually agree on the 50K myself. My labor was 15 hrs and 5 hrs of pushing, all natural. There is no comparison between anything physical activity and labor; no summiting peaks or marathons can top it. It is truly the most physical thing the human body can do. As a black belt martial artist, Kajukenbo, I really believe that. Much harder than fighting for 4-5 hours straight. So I totally believe it. But I'm no scientist. :) Just a bad-ass mom.

Otis said...

@Jewels,
That figure seems within the realm of possibility. There's probably some other water-weight loss too due to sweat; and of course things will vary widely depending upon if you have a 2 hour labor or a 2 day labor.

@MollyNPaul
Just because you want to believe something doesn't make it true. To burn 50,000 calories, we can assume that labor is much less intense than pushing. Having witnessed labor a few times it's likely in the realm of 300 cal/hr for a 150lbs woman. So 15 hours of that is about 4500 calories. Which means you still have to burn 45,500 more calories in those 5 hours of pushing. The burn rate during your pushing was 9,100 calories per hour (about the same as burned during 2 5-hour stages of the tour-de-france). That falls in to the realm of absurdity. You simply cannot burn that many calories in that timeframe, no matter how much you 'believe' it or not.

Was it the hardest thing you've ever done? Sure.
Did you burn a lot of calories? Likely so.
Did you burn 50,000 calories in 15-20 hours? Absolutely, unequivocally no.

Ultimately I can't change the mind of somebody who wants to believe something. But belief in something in spite of strong contradictory evidence is not a good path to go down. It's a natural path, it's an easy path, but it's ultimately a bad path to take.

As homework, I would recommend taking a look at and listening to this:
http://kut.org/post/why-we-keep-holding-false-beliefs

Lola said...

You pushed for 5 hours? What kind of crazy doctor would allow such insanity? Really, I want to know so I don't ever mistakenly hire him/her as my OB.

Felicia Winnett said...

So...what is the approximate equation to estimate calories lost? You debunked the 50k myth, but didn't actually provide an answer. While I know every labor is different, it doesn't mean an estimate can't be made.

Otis said...

@Felicia,
The actual variables are many. Somebody that has a 3 hour labor and delivery under full epidural likely doesn't burn more than a few hundred calories above baseline.

A strenuous 24 hour labor with no pain killers likely would burn more calories. But even then, birth doesn't engage your primary calorie burning muscle groups. For example, doing ab crunches doesn't burn nearly as many calories as doing repeats on stadium stairs.

I haven't seen any actual data on it, so I'm not going to claim a particular number. But I would posit that the body likely burns more calories in the recovery process than it does on the actual birth for most cases. Replenishing lost blood, healing, and building milk supplies likely are much more calorically intensive. The actual birth is probably calorically on-par with a hard workout; but no matter which way you slice it, one cannot physically burn 50,000 calories during birth; and that is why I made this post to debunk such a ridiculous claim.

Gina Bonfante said...

I pushed for 4 and begged my ob to let me have a break. I can't imagine doing another hour of that!!!

Cristina Bolocan said...

I only know facts from my own experience, delivered 8 lb baby, all my muscles were sore for days, got weighted after one week from the baby's delivery and I was 15 lb less

Otis said...

@Cristina,
That's actually right in line with expected weight loss of around 17lbs between being pregnant and 1 week after giving birth.

8 lbs for the Baby
4 lbs for the placenta and amniotic fluid
5 lbs for water loss in week following

http://www.livestrong.com/article/263022-how-much-weight-does-a-woman-lose-when-giving-birth/