Intermittent Fasting Fail

Emily Oster

2 min Read Emily Oster

Emily Oster

Intermittent Fasting Fail

New study suggests it’s not special

Emily Oster

2 min Read

First, thanks for being a ParentData reader. I really appreciate it; it means a lot to have your support. In return for this, you get to hear me rant about diet study data.

Back in January, I wrote about the “best” diet strategy for health. The conclusion was decidedly not that there is some great diet you’re missing. It was mostly that there is no single best diet for heart health or any other outcome, and that we do not know very much. It was pointed out to me after I sent it that I should also have been clearer that most diets fail and that diet culture is extremely problematic. Point taken.

Today, though, I want to do something that I think is slightly less fraught and just unpack one particular study, published in the New England Journal of Medicine a few weeks ago, that discusses intermittent fasting. The TL;DR is that it did not find that weight loss was greater with intermittent fasting than with simple calorie restriction. But let’s dive in.

This study is a randomized trial that enrolled 139 obese patients in China. The patients were divided into two groups. Both groups were instructed to follow a restricted-calorie diet (1,500 to 1,800 calories a day for men, 1,200 to 1,500 for women). One group, the fasting group, was told to eat only between 8 a.m. and 4 p.m. The other group was allowed to eat whenever, but with the same calorie restriction.

Participants were followed for 12 months. The main result on weight loss can be seen in the graph below. “DCR” is the calorie-restricted diet without time restriction, and “TRE” is the time-restricted version. As with virtually all diets: weight loss is initially steep, then plateaus before slightly rebounding. Although the time-restricted eating group loses slightly more weight in the first three months, there is no significant difference by 6 or 12 months in the amount of weight loss.

The authors look at all kinds of other outcomes, including blood pressure, fasting glucose, and body fat, and do not see any significant differences across the groups.

If you dig a bit deeper into the supplementary tables of the paper, it seems clear why we do not see differences across groups: there is no difference in their calorie intake. The graph below shows the measured calories for each group over the study period. (Note: Reported calorie intake is generally a large underestimate of actual calorie intake, so these numbers are likely too small, both before and after. However, the comparison across groups should capture differences.) Both groups show an initial large reduction in calorie intake, followed by a gradual increase back toward baseline.

The bottom line isn’t that intermittent fasting is worse than another diet option. It’s just that it’s not any better. Based on this follow-up, it shows the same profile as a standard approach: some weight loss, followed by some rebound.

Stepping back, there are really two reasons you might have thought intermittent fasting was a “better” option, both of which I think are rendered less plausible by these data.

One is the idea that intermittent fasting could work because it is easier to adhere to. I will confess to having had this instinct at various times. Diet rules are often complicated — calorie counting, nutrient comparison, etc. The rule “Don’t eat from 8 p.m. to noon” (or whatever it is) is at least easy to follow. Since adherence to diet is basically the whole thing in terms of long-term success, a diet that is easier to stick with could be better. In this study, we do not see evidence of that. The intermittent fasting diet does not have better adherence than with standard calorie restriction.

The other possibility is that there is something inherently health-promoting about going longer periods without eating. The idea would be that even with the same calorie intake, having periods of fasting improves heart health or some other outcome. That doesn’t appear to be the case based on these data. The calorie and weight reduction are similar, and there are no differential improvements in heart or metabolic health.

On the more positive side, both diets report the same number of adverse events, and these are generally mild (basically, people are hungry).

What do we take from this overall? I would say it’s simply that there isn’t something magic about intermittent fasting. If it is an approach to eating that works for you, fine. But there is still no “best” diet.

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Potty training can feel like a Mount Everest-size challenge, and sadly, our evidence-based guidance is poor. So, I created a survey to collate advice and feedback on success from about 6,000 participants.

How long does potty training take? We found that there is a strong basic pattern here: the later you wait to start, the shorter time it takes to potty train. On average, people who start at under 18 months report it takes them about 12 weeks for their child to be fully trained (using the toilet consistently for both peeing and pooping). For those who start between 3 and 3.5, it’s more like nine days. Keep in mind that for all of these age groups, there is a range of length of time from a few days to over a year. Sometimes parents are told that if you do it right, it only takes a few days. While that is true for some people, it is definitely not the norm.

If you’re in the throes of potty training, hang in there! 

#emilyoster #parentdata #pottytraining #pottytrainingtips #toddlerlife

Potty training can feel like a Mount Everest-size challenge, and sadly, our evidence-based guidance is poor. So, I created a survey to collate advice and feedback on success from about 6,000 participants.

How long does potty training take? We found that there is a strong basic pattern here: the later you wait to start, the shorter time it takes to potty train. On average, people who start at under 18 months report it takes them about 12 weeks for their child to be fully trained (using the toilet consistently for both peeing and pooping). For those who start between 3 and 3.5, it’s more like nine days. Keep in mind that for all of these age groups, there is a range of length of time from a few days to over a year. Sometimes parents are told that if you do it right, it only takes a few days. While that is true for some people, it is definitely not the norm.

If you’re in the throes of potty training, hang in there!

#emilyoster #parentdata #pottytraining #pottytrainingtips #toddlerlife
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For children or adults with severe food allergies, they can be incredibly scary and restrictive. We may imagine that it’s easy to deal with a peanut allergy by, say, not eating peanut butter sandwiches. But for someone with a severe version of this allergy, they may never be able to go to a restaurant, for fear of a severe reaction to something in the air. Right now, there’s only one approved treatment for severe allergies like this and it’s limited to peanuts.

This is why the new medication Xolair is very exciting. It promises a second possible treatment avenue and one that works for other allergens. A new trail analyzed data from 177 children with severe food allergies. Two-thirds of the treatment group were able to tolerate the specified endpoint, versus just 7% of the placebo group. This is a very large treatment effect, and the authors found similarly large impacts on other allergens. 

There are some caveats: This treatment won’t work for everyone. (One-third of participants did not respond to it.) Additionally, this treatment is an injection given every two to four weeks, indefinitely. This may make it less palatable to children. 

Overall, even with caveats, this is life-changing news for many families!

#xolair #foodallergies #allergies #peanutallergy #emilyoster #parentdata

For children or adults with severe food allergies, they can be incredibly scary and restrictive. We may imagine that it’s easy to deal with a peanut allergy by, say, not eating peanut butter sandwiches. But for someone with a severe version of this allergy, they may never be able to go to a restaurant, for fear of a severe reaction to something in the air. Right now, there’s only one approved treatment for severe allergies like this and it’s limited to peanuts.

This is why the new medication Xolair is very exciting. It promises a second possible treatment avenue and one that works for other allergens. A new trail analyzed data from 177 children with severe food allergies. Two-thirds of the treatment group were able to tolerate the specified endpoint, versus just 7% of the placebo group. This is a very large treatment effect, and the authors found similarly large impacts on other allergens.

There are some caveats: This treatment won’t work for everyone. (One-third of participants did not respond to it.) Additionally, this treatment is an injection given every two to four weeks, indefinitely. This may make it less palatable to children.

Overall, even with caveats, this is life-changing news for many families!

#xolair #foodallergies #allergies #peanutallergy #emilyoster #parentdata
...

If you have a fever during pregnancy, you should take Tylenol, both because it will make you feel better and because of concerns about fever in pregnancy (although these are also overstated).

The evidence that suggests risks to Tylenol focuses largely on more extensive exposure — say, taking it for more than 28 days during pregnancy. There is no credible evidence, even correlational, to suggest that taking it occasionally for a fever or headache would be an issue.

People take Tylenol for a reason. For many people, the choice may be between debilitating weekly migraines and regular Tylenol usage. The impacts studies suggest are very small. In making this decision, we should weigh the real, known benefit against the suggestion of this possible risk. Perhaps not everyone will come out at the same place on this, but it is crucial we give people the tools to make the choice for themselves.

#emilyoster #parentdata #tylenol #pregnancy #pregnancytips

If you have a fever during pregnancy, you should take Tylenol, both because it will make you feel better and because of concerns about fever in pregnancy (although these are also overstated).

The evidence that suggests risks to Tylenol focuses largely on more extensive exposure — say, taking it for more than 28 days during pregnancy. There is no credible evidence, even correlational, to suggest that taking it occasionally for a fever or headache would be an issue.

People take Tylenol for a reason. For many people, the choice may be between debilitating weekly migraines and regular Tylenol usage. The impacts studies suggest are very small. In making this decision, we should weigh the real, known benefit against the suggestion of this possible risk. Perhaps not everyone will come out at the same place on this, but it is crucial we give people the tools to make the choice for themselves.

#emilyoster #parentdata #tylenol #pregnancy #pregnancytips
...

Parenting trends are like Cabbage Patch Kids: they’re usually only popular because a bunch of people are using them! Most of the time, these trends are not based on new scientific research, and even if they are, that new research doesn’t reflect all of what we’ve studied before.

In the future, before hopping onto the latest trend, check the data first. Unlike Cabbage Patch Kids, parenting trends can add a lot of unnecessary stress and challenges to your plate. What’s a recent trend that you’ve been wondering about?

#parentdata #emilyoster #parentingtips #parentingadvice #parentinghacks

Parenting trends are like Cabbage Patch Kids: they’re usually only popular because a bunch of people are using them! Most of the time, these trends are not based on new scientific research, and even if they are, that new research doesn’t reflect all of what we’ve studied before.

In the future, before hopping onto the latest trend, check the data first. Unlike Cabbage Patch Kids, parenting trends can add a lot of unnecessary stress and challenges to your plate. What’s a recent trend that you’ve been wondering about?

#parentdata #emilyoster #parentingtips #parentingadvice #parentinghacks
...

As of this week, 1 million copies of my books have been sold. This feels humbling and, frankly, unbelievable. I’m so thankful to those of you who’ve read and passed along your recommendations of the books.

When I wrote Expecting Better, I had no plan for all of this — I wrote that book because I felt compelled to write it, because it was the book I wanted to read. As I’ve come out with more books, and now ParentData, I am closer to seeing what I hope we can all create. That is: a world where everyone has access to reliable data, based on causal evidence, to make informed, confident decisions that work for their families.

I’m so grateful you’re all here as a part of this, and I want to thank you! If you’ve been waiting for the right moment to sign up for full access to ParentData, this is it. ⭐️ Comment “Link” for a DM with a discount code for 20% off of a new monthly or annual subscription to ParentData! 

Thank you again for being the best community of readers and internet-friends on the planet. I am so lucky to have you all here.

#parentdata #emilyoster #expectingbetter #cribsheet #familyfirm #parentingcommunity

As of this week, 1 million copies of my books have been sold. This feels humbling and, frankly, unbelievable. I’m so thankful to those of you who’ve read and passed along your recommendations of the books.

When I wrote Expecting Better, I had no plan for all of this — I wrote that book because I felt compelled to write it, because it was the book I wanted to read. As I’ve come out with more books, and now ParentData, I am closer to seeing what I hope we can all create. That is: a world where everyone has access to reliable data, based on causal evidence, to make informed, confident decisions that work for their families.

I’m so grateful you’re all here as a part of this, and I want to thank you! If you’ve been waiting for the right moment to sign up for full access to ParentData, this is it. ⭐️ Comment “Link” for a DM with a discount code for 20% off of a new monthly or annual subscription to ParentData!

Thank you again for being the best community of readers and internet-friends on the planet. I am so lucky to have you all here.

#parentdata #emilyoster #expectingbetter #cribsheet #familyfirm #parentingcommunity
...

Just eat your Cheerios and move on.

Just eat your Cheerios and move on. ...

The AAP’s guidelines recommend sleeping in the same room as your baby “ideally for the first six months.” However, the risk of SIDS is dramatically lower after four months, and the evidence in favor of the protective effect of room sharing is quite weak (both overall and even more so after four months). There is also growing evidence that infants who sleep in their own room by four months sleep better at four months, better at nine months, and even better at 30 months.

With this in mind, it’s worth asking why this recommendation continues at all — or at least why the AAP doesn’t push it back to four months. They say decreased arousals from sleep are linked to SIDS, which could mean that babies sleeping in their own room is risky. But this link is extremely indirect, and they do not show direct evidence to support it.

According to the data we have, parents should sleep in the same room as a baby for as long as it works for them! Sharing a room with a child may have negative impacts on both child and adult sleep. We should give families more help in navigating these trade-offs and making the decisions that work best for them.

#emilyoster #parentdata #roomsharing #sids #parentingguide

The AAP’s guidelines recommend sleeping in the same room as your baby “ideally for the first six months.” However, the risk of SIDS is dramatically lower after four months, and the evidence in favor of the protective effect of room sharing is quite weak (both overall and even more so after four months). There is also growing evidence that infants who sleep in their own room by four months sleep better at four months, better at nine months, and even better at 30 months.

With this in mind, it’s worth asking why this recommendation continues at all — or at least why the AAP doesn’t push it back to four months. They say decreased arousals from sleep are linked to SIDS, which could mean that babies sleeping in their own room is risky. But this link is extremely indirect, and they do not show direct evidence to support it.

According to the data we have, parents should sleep in the same room as a baby for as long as it works for them! Sharing a room with a child may have negative impacts on both child and adult sleep. We should give families more help in navigating these trade-offs and making the decisions that work best for them.

#emilyoster #parentdata #roomsharing #sids #parentingguide
...

It was an absolute pleasure to be featured on the @tamronhallshow! We talked about all things data-driven parenting and, in this clip, what I call the plague of secret parenting. To balance having a career and having a family, we can’t hide the fact that we’re parents. If mothers and fathers at the top can speak more openly about child-care obligations, it will help us all set a new precedent.

Watch the full segment at the link in my bio 🔗

#tamronhall #tamronhallshow #emilyoster #parentingsupport #workingparents

It was an absolute pleasure to be featured on the @tamronhallshow! We talked about all things data-driven parenting and, in this clip, what I call the plague of secret parenting. To balance having a career and having a family, we can’t hide the fact that we’re parents. If mothers and fathers at the top can speak more openly about child-care obligations, it will help us all set a new precedent.

Watch the full segment at the link in my bio 🔗

#tamronhall #tamronhallshow #emilyoster #parentingsupport #workingparents
...

Invisible labor. It’s the work — in our households especially — that has to happen but that no one sees. It’s making the doctor’s appointment, ensuring birthday cards are purchased, remembering the milk.

My guest on this episode, @everodsky, has come up with a solution here, or at least a way for us to recognize the problem and make our own solutions. I’ve wanted to speak with Eve for ages, since I read her book Fair Play. We had a great conversation about the division of household labor, one I think you’ll get a lot out of!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#emilyoster #parentdata #parentdatapodcast #parentingpodcast #householdtips #fairplay #invisiblelabor

Invisible labor. It’s the work — in our households especially — that has to happen but that no one sees. It’s making the doctor’s appointment, ensuring birthday cards are purchased, remembering the milk.

My guest on this episode, @everodsky, has come up with a solution here, or at least a way for us to recognize the problem and make our own solutions. I’ve wanted to speak with Eve for ages, since I read her book Fair Play. We had a great conversation about the division of household labor, one I think you’ll get a lot out of!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#emilyoster #parentdata #parentdatapodcast #parentingpodcast #householdtips #fairplay #invisiblelabor
...

Prenatal vitamins 💊 If there is any product that seems designed to prey on our fears, it’s this one. You’re newly pregnant and you want to do it right. Everyone agrees you need prenatal vitamins, so you get them. But do you want to be that person who just… buys the generic prenatal vitamins?

Good news: fancier vitamins are not better.  Folic acid is the most important prenatal ingredient. Iron (with vitamin C) and DHA are also nice to have. Other included ingredients have only weak or no evidence to support their use. (If you do not consume animal products, add B12, plus a few others depending on your diet.)

Vitamins are just vitamins. Any prenatal vitamin that contains these is enough. 

Comment “Link” for a DM to an article with everything you need to know about prenatal vitamins.

#emilyoster #parentdata #prenatalvitamins #pregnancydiet #pregnancytips

Prenatal vitamins 💊 If there is any product that seems designed to prey on our fears, it’s this one. You’re newly pregnant and you want to do it right. Everyone agrees you need prenatal vitamins, so you get them. But do you want to be that person who just… buys the generic prenatal vitamins?

Good news: fancier vitamins are not better. Folic acid is the most important prenatal ingredient. Iron (with vitamin C) and DHA are also nice to have. Other included ingredients have only weak or no evidence to support their use. (If you do not consume animal products, add B12, plus a few others depending on your diet.)

Vitamins are just vitamins. Any prenatal vitamin that contains these is enough.

Comment “Link” for a DM to an article with everything you need to know about prenatal vitamins.

#emilyoster #parentdata #prenatalvitamins #pregnancydiet #pregnancytips
...

When it comes to introducing your newborn to the world, timing matters. It’s a good idea to minimize germ exposure in the first 6-8 weeks; after that, it’s inevitable and, very likely, a good idea! This doesn’t mean you need to be trapped inside. The most significant exposure risks are from seeing other people at home — family, etc. These interactions are not infinitely risky, but they do pose more risk than a walk or a trip to the grocery store, since they involve closer interaction. Think simple and make sure everyone is washing their hands before holding the baby. 💛

#parentdata #emilyoster #newborncare #parentingadvice #parentingtips

When it comes to introducing your newborn to the world, timing matters. It’s a good idea to minimize germ exposure in the first 6-8 weeks; after that, it’s inevitable and, very likely, a good idea! This doesn’t mean you need to be trapped inside. The most significant exposure risks are from seeing other people at home — family, etc. These interactions are not infinitely risky, but they do pose more risk than a walk or a trip to the grocery store, since they involve closer interaction. Think simple and make sure everyone is washing their hands before holding the baby. 💛

#parentdata #emilyoster #newborncare #parentingadvice #parentingtips
...

The first edition of Hot Flash is out now! Comment “Link” for a DM to learn more about the late-reproductive stage.

There are times when we expect hormonal shifts. Our reproductive lives are bookended by puberty and menopause. We discuss those changes often because they are definitive and dramatic — a first period is something many of us remember clearly. But between ages 13 and 53, our hormones are changing in more subtle ways. During the late-reproductive stage (in your 40s), you can expect a lot of changes in your menstrual cycle, including the length and symptoms you experience throughout. It’s an important time in our lives that is often overlooked!

🔥 Hot Flash from ParentData is a weekly newsletter on navigating your health and hormones in the post-reproductive years. Written by Dr. Gillian Goddard, Hot Flash provides all of the information you need to have a productive, evidence-based conversation about hormonal health with your doctor.

#emilyoster #parentdata #hotflash #perimenopause #womenshealth

The first edition of Hot Flash is out now! Comment “Link” for a DM to learn more about the late-reproductive stage.

There are times when we expect hormonal shifts. Our reproductive lives are bookended by puberty and menopause. We discuss those changes often because they are definitive and dramatic — a first period is something many of us remember clearly. But between ages 13 and 53, our hormones are changing in more subtle ways. During the late-reproductive stage (in your 40s), you can expect a lot of changes in your menstrual cycle, including the length and symptoms you experience throughout. It’s an important time in our lives that is often overlooked!

🔥 Hot Flash from ParentData is a weekly newsletter on navigating your health and hormones in the post-reproductive years. Written by Dr. Gillian Goddard, Hot Flash provides all of the information you need to have a productive, evidence-based conversation about hormonal health with your doctor.

#emilyoster #parentdata #hotflash #perimenopause #womenshealth
...

There are plenty of reels telling you how to parent. Plenty of panic headlines saying that “studies show” what’s best for your kid. Even good data, from a trusted source, can send us into a spiral of comparison. But I want you to remember that no one knows your kid better than you. It’s important to absorb the research, but only you will know the approach that works best for you and your child. 💙

Now tell me in the comments: what’s a parenting move you’ve made recently that feels right to you?

#parentingcommunity #parentingsupport #parentingquotes #emilyoster #parentdata

There are plenty of reels telling you how to parent. Plenty of panic headlines saying that “studies show” what’s best for your kid. Even good data, from a trusted source, can send us into a spiral of comparison. But I want you to remember that no one knows your kid better than you. It’s important to absorb the research, but only you will know the approach that works best for you and your child. 💙

Now tell me in the comments: what’s a parenting move you’ve made recently that feels right to you?

#parentingcommunity #parentingsupport #parentingquotes #emilyoster #parentdata
...

Let’s talk about sex (after) baby! Today on the podcast, I was lucky enough to speak with @enagoski about her new book on sexual connection in long-term relationships. Especially after having kids, this is something many people struggle with. Emily tells us to stop worrying about what’s “normal” and focus on pleasure in its many forms.

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #parentdatapodcast #emilyoster #emilynagoski #comeasyouare #cometogether #longtermrelationship #intimacy #relationships

Let’s talk about sex (after) baby! Today on the podcast, I was lucky enough to speak with @enagoski about her new book on sexual connection in long-term relationships. Especially after having kids, this is something many people struggle with. Emily tells us to stop worrying about what’s “normal” and focus on pleasure in its many forms.

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #parentdatapodcast #emilyoster #emilynagoski #comeasyouare #cometogether #longtermrelationship #intimacy #relationships
...

Ever wondered if you can safely use leftover baby formula? 🍼 The CDC says to throw out unused formula immediately because of the risk of bacterial growth. However, research suggests that bacterial concentrations do not appreciably increase after 3, 12, or even 24 hours at refrigerator temperatures. Good news! This means there’s not a strong data-based reason to throw out formula right away if you store it in the fridge.

Comment “Link” for a DM to an article on another common formula question: should you throw away old formula powder?

#emilyoster #parentdata #babyformula #babyfeeding #parentingstruggles

Ever wondered if you can safely use leftover baby formula? 🍼 The CDC says to throw out unused formula immediately because of the risk of bacterial growth. However, research suggests that bacterial concentrations do not appreciably increase after 3, 12, or even 24 hours at refrigerator temperatures. Good news! This means there’s not a strong data-based reason to throw out formula right away if you store it in the fridge.

Comment “Link” for a DM to an article on another common formula question: should you throw away old formula powder?

#emilyoster #parentdata #babyformula #babyfeeding #parentingstruggles
...

What’s the most important piece of advice for new parents? Here’s one answer, but I want to hear from you! Share your suggestions in the comments ⬇️

#emilyoster #parentdata #parentingtips #parentingadvice #newparents #parentingcommunity

What’s the most important piece of advice for new parents? Here’s one answer, but I want to hear from you! Share your suggestions in the comments ⬇️

#emilyoster #parentdata #parentingtips #parentingadvice #newparents #parentingcommunity
...

What's in the bag of a Vagina Economist? 👀 Someone please tell me this looks familiar to you.

What`s in the bag of a Vagina Economist? 👀 Someone please tell me this looks familiar to you. ...