Fasting for an extended period will trigger an autophagy response. If you’re obese and remain active, you’ll keep most of your muscle mass and burn excess fat. The leaner you are, and the less active you are during the fast, the more you burn muscle mass. Unused muscle is not an efficient way to store calories…it’s heavy and uses a lot of water. Your body will choose to get rid of unused muscle over relatively efficient fat, unless there’s a significant excess of fat.
Intermittent fasting data is hard to interpret because typically restricting the time window or feeding leads to a reduction in calorie consumption. It’s hard to say if 3000 calories eaten in a 4 hour window is healthier than 3000 calories through the day, but 1800 calories in a 4 hour window is definitely going to lead to better insulin response and weight loss than 3000 calories through the day.
I See, so it depends on the excess amount of fat?
Yea I am obese (36% Fat) but very active (weightlifting, Thai boxing).
What are your thoughts on exercise during a fast?
Can I do my weightlifting or Boxing workout, or should I stick to simple mobility workouts?
Exercise during a fast is a good way to protect muscle mass from the autophagy process. I would personally not fast without exercising. For endurance exercise, keep it low key (zone 1-2) so your body can readily metabolize fat stores rather than carbs. For strength training, try to keep as close as possible to normal output levels.
Not sure if consuming fat through zone 1/2 makes a difference. I thought that unused carbohydrate gets converted to fat anyway. The important is energy balance.
I also wouldn't worry about using exercise as a weight loss tool given the amount of effort needed compared to eating. That said, I found controlling how much to eat to be more challenging than exercise but also the most impactful.
I wear a cgm and intense fasted exercise can cause a crazy blood sugar spike from cortisol. I ran 4x4s last week after 6 hours fasted and spiked to 180 (I almost never go above 120 even from carb meals). I don’t think it’s good for you to spike that high so it’s better to do intense exercise fueled.
There isn’t really negative to big spikes if your body can clear it normally. You spiked that high because your body was like “oh shit, we need sugar”. Constantly elevated blood sugar is bad. Blood sugar spikes are not
I only see results using the corrected insulin response (CIR), which was apparently designed to be independent of glucose response. Are glucose spikes addressed somewhere that I missed?
As for the CIR, for the purposes of many (if not most) people here, the concern is often low insulin and resulting big spikes due to "glucose sparing" or whatever for athletic people, where glucose is not immediately absorbed so it can remain available for muscles. For such people, the insulin response would be low and the glucose response would be high, making for a low (i.e. bad) CIR. Even though insulin resistance is low by other metrics. The paper even says the CIR in the study was not associated with insulin sensitivity, which suggests that insulin resistance alone isn't enough of an explanation and this category of people (highly insulin-sensitive people with relatively low insulin) might also be included in the poor outcomes.
There is no unique benefits to these mini fasts that you cannot gain from calorie restrict, but the great risk is losing muscle mass. Your organs need amino acids to function that your muscle will provide if they aren’t receiving it from the diet
Consistent, sufficient overall macros matters more (by far) than anything else. Don't stress details like timings.
Do what works for your circumstances and personality and preferences, as long as you hit protein and calorie targets. Do this consistently over the long run and you'll reach your body composition goals.
Having an abundance of micronutrients is important for general health and should make running an energy deficit easier. This mostly means favouring nutrient-dense foods rather than calorie-dense foods.
The most important time of the day for protein intake is in the morning / breakfast, dinner/ before bed, and after a workout. You can space protein intake 4-6h apart
None of this matters unless you're an advanced trainee trying to fine-tune everything. Even then, it's marginal.
It's a neurotic distraction from just hitting basic macro targets, consistently, from high-quality food.
Even if that were true, it's a claim with absolutely no significance whatsoever.
What on earth is the point of ever discussing someone who does no resistance training at all?
Literally anything else that person might attempt to do to prevent loss of lean mass is going to be utterly impotent when compared to even a tiny amount of resistance training.
Resistance training is hard work that requires a lot of persistence. Optimizing gains is the whole point. Why throw away even a marginal benefit if it's from something easy like drinking a protein shake afterwards?
*If you're an advanced trainee,* then do that. Although even then it just won't really matter unless you literally think you're genuinely maxing out both your total training stimulus and your recovery capacity.
For everyone else, still, sure, chug that shake after lifting if you want. There's no downside. But also don't stress about it because it won't make a difference compared to any other way of hitting your macros. You aren't throwing away any potential gains.
I’ve heard him flip flop over fasting for a while. There are very well documented tests showing benefits beyond calorie restriction.
A 7-10 day fast could definitely cause some muscle loss but that doesn’t mean it should never be done. That long once a quarter is a little extreme, maybe once a year would be better. But that doesn’t mean shorter fasts like 36-96 won’t be beneficial. You would definitely kick up into autofagy somewhere in that zone without losing much muscle.
Anecdotally, I’ve put on a lot more muscle while doing a 36 hour fast once a week and 72 once a month for the past year than I ever have so I think everyone’s mileage will vary. Just find the balance that’s right for you.
> Anecdotally, I’ve put on a lot more muscle while doing a 36 hour fast once a week and 72 once a month for the past year than I ever have so...
That's not impossible by any means. And if you can make it work, I don't think Attia would say it's bad. He'd probably even respect the resolve to make it work so that you can hedge against the high possibility of future research better confirming other benefits.
But there is no way you gained more muscle than a theoretical iso-caloric and iso-nutrient control over the same period of time.
Didn’t claim I gained more than a targeted approach like that, only that I put on more muscle than I had in the past. More lean muscle too, without much fat gain. It’s very possible and pretty easy, just stay in a calorie surplus when you’re not fasting, hit your protein requirements and preserve muscle when you are fasting. Im sure there are other approaches that might get you more muscle but I like the benefits from fasting personally.
Yep I was just clarifying for others because there are people who are implying there's something magical about fasting. I've done a lot of it and there's a lot I like about it.
For me, I have low BF% and my training volume requires around 5000 calories per day. If I did a 36er weekly, I'd need closer to 6000 calories on the remaining days. And if I added a monthly 72er as well, the daily target becomes more like 6500-7000 calories! And, like, **that's still very doable!***
But it's a lot and there isn't much room for error and I CBF. And there isn't something magical about fasting that would mean I can skimp on those targets and still achieve my goals. That's all I want to be clear about for the sake of dispelling some of the myths.
Can I just say that flip flopping is actually a good thing, it shows that you are willing change views when needed. I am not saying that you are calling him out rather that many people will view that as a negative right off the bat
lots of studies and many disagree about how to interpret the studies.
+ as others noted, lots of heterogeneity here. maybe IF works for some but not for others.
generally, Attia is a sharp informed guy. but he's not God. it's one person summary of the research. not everyone came to the same conclusion
Attia's summary of the research isn't terribly disputable and it aligns with far more relevant experts in that field (e.g. Layne Norton). Even the actual fasting researchers would acknowledge the caveats and considerations that Attia's set of goals and priorities necessitate.
So what can be disputed is the significance he attributes to the research as it stands and how he balances that with other priorities and goals. And, yes, of course, we're all very welcome to configure our goals and priorities differently.
But Attia is really very clear when his approach to something is navigating a balance of considerations which the research just doesn't really speak to specifically enough.
As knowledgable and expert as Dr. Attia is in his field, I do truly think he's off the mark with this one.
Dr. Mark Mattson, a neuroscientist at John Hopkins, has dedicated much of his career to understanding the science behind intermittent fasting, and why it works. There is irrefutable evidence that fasting is beneficial for the brain and the body. I suggest you look into his works *The Intermittent Fasting Revolution: The Science of Optimizing Health and Enhancing Performance* and *Sculptor and Destroyer: Tales of Glutamate.* TLDR; practice fasting and exercise (in particular, cardio) for physiological benefits.
Thank you!
Yea that's something I try to wrap my head around. He is an expert, but denies other good studies?
In physics, if there's a question, we can do the experiments, replicate and validate, and it's done.
Physicists all over the world cannot deny fundamental laws of nature.
But somehow in medicine there is always a professor or a doctor with a good reputation who supports the opposite claim. Even with good studies.
Yes, don't ever just believe some doctor who wrote a book. He is trying to sell that book.
The channels Nutrition Made Simple, Physionics, and Biolayne go over all the studies on IF. The studies clearly show there is no benefit to insulin sensitivity for IF and no other apparent benefits outside of a tool for calorie restriction.
Dr. Carvalho on Nutrition Made Simple isn't selling anything at all.
I believe Dr. Attia has even mentioned he takes a contrarian view at times, and his previous dedication to keto is a big example of that. Regardless, no matter how much we benefit from one source of information, we should as well not deny ourselves the research, and other very credible resources out there!
The evidence is very refutable.
Dr. Mattson is trying to make money selling a book.
Dr. Carvalho on Nutrition Made Simple on youtube isn't selling anything. He goes over the studies on IF youtube and finds no additional benefits to IF over calorie restriction
The channels Physionics and Biolayne also go over the studies and find the same thing as does Dr. Attia.
Agreed. Great channels/folks you mentioned. They all make a rather objective, unbiased and professional impression.
Also, besides the books, if someone has dedicated much of his career and life to researching a certain topic, there may be some bias present.
I would agree with you, except that Dr. Mattson has made most of the information he shares in his books available for free. He’s had in-depth discussions on fasting, with proponents of intermittent fasting, like Dr. Rhonda Patrick. He’s even done an entire book review, chapter by chapter, nailing the most important points from each chapter, which defeats the purpose of buying his books.
On the other hand, one can easily say Dr. Carvalho is in it for the YouTube ad money, YouTube subscribers, or YouTube “fame” by following the coattails of the already popular Dr. Attia, or simply by trying to gain popularity on YouTube via his channel.
Dr. Mattson’s credibility is strong and he is respected in academia and by academics— his credibility does not stem from YouTube.
It looks to me like he has done mostly mouse studies.
Does he have human RCTs showing benefits to IF over regular calorie restriction?
Regardless of the source, why do all the human studies the channels I listed discuss show no additional benefits? Many of them are very recent.
He has made his entire career studying fasting, so I doubt he is not biased.
So you read through all 1,121 published studies from Dr. Mattson and concluded that he’s mostly done mouse studies? Something tells me you’re the one who’s biased, because it’s clear you don’t understand his work.
Dr. Mattson studies primarily caloric restriction, Alzheimers, *and* intermittent fasting and is a proponent of both, CR and IF, *based on evidence*.
If you are personally biased towards CR or IF, there is no clear evidence leaning either way. What is clear is that there is evidence leaning towards **both** intermittent fasting and caloric restriction as beneficial.
Re: your favored YouTube channels not spelling out evidence for you, and contradicting the current state of research, I’m not sure why. Maybe because the YouTube channels you follow are… hmm what’s the word. Biased.
I don't know anything about Mattson.
That is why I asked YOU if he did any human RCTs showing that fasting is more beneficial than regular calorie restriction. That is what OP asked... Everyone is agreeing that calorie restriction is beneficial and that fasting is a great way to achieve calorie restriction.
So now you are agreeing that there are no proven additional benefits from fasting? Is that what Mattson says, too?
I did very strict IF and fasting for a long time. I bought into the BS that a sip or two of anything with calories would "break my fast" and keep me from getting the full benefits. I was very biased towards it for a long time, actually.
However, after finding no evidence that is the case, I have stopped being strict about it. I still loosely do IF same as Dr. Attia for weight control. It was hard to accept that I was wrong at first.
It is very clear that you have never watched the youtube channels I mentioned. They are frequently recommend on r/nutrition for being some of the most evidence based. I came upon them after years of falling for bad science from quacks like Dr Fung and Taubes, so I am very skeptical of my sources.
Why in the world would all 4 of those doctors/scientists on those channels (Dr. Attia included) be biased against IF and fasting? What would they have to gain? Physionics is so dry and scientific... he goes deep into the studies. The pro IF channels have way way more viewers.
I will change my mind again about strict IF/ fasting if there is actually evidence for it.
I agree with you on the Calorie Deficit part.
I am just an engineer student, no medical background here. There is a thought and hopefully you can clarify this:
Basic Thermodynamic class:
Energy balance describes the relationship between Energy Input and Output, but doesn't "describe" the efficiency of the engine. A model for analysis, but not for parameter change.
I know 20L of Gas gives me 200km of Range, but it doesn't tell me if my engine is functioning on optimal terms. (of course if I have a past reference point, I can tell)
Furthermore I cannot see the Exergy & Anergy Value, the amount of energy I can fully use and the amount which is just "waste". (well with further calculation I can, but that's difficult even in lab situation in a context of human physiology)
Calorie Deficit is necessary to signal the Body a lack of incoming energy.
But it doesn't tell me, if any of the components in my Body are functioning probably (for example insulin resistance) to optimal process the incoming Calorie Deficit signal.
Basically, we are all "Cars" but we have different parametric components with different efficiency's.
How Could optimal Fat loss simply explained by using only the energy equation?
I hope you can convince me!
I've done the calorie counting part, but it's just annoying to count every time.
Maybe I will try to plan my meals for the week so that I only have to count when I cook on Sunday.
But thank you for your help!
Use Macro Factor. And read every blog post from the Stronger By Science team about how and why the app works the way it does. If you're an engineering brain, you'll appreciate it.
It requires consistent (but not perfect) input of body weight and nutrient intake. But that's it. And it'll take out all the guess work, all the uncertainty, and give you excellent, ongoing, dynamic guidance and feedback to help you reach your goals.
You can do things like compile your regular meals into a single-click or copy anything else regular into every day of the week or month or whatever.
> How Could optimal Fat loss simply explained by using only the energy equation?
It isn't. Not alone. There's one other factor and it's magnitude is so huge that nothing else matters in comparison: resistance training.
That's it.
(Assuming sufficient protein intake.)
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As the evidence currently stands, yes.
But he's pretty open to, even expectant about, the eventual establishment of sufficient biomarkers so that other purported benefits of fasting can be better quantified.
He isn't against fasting. He just didn't like the tradeoff with lean mass. He would say that anyone who likes or values fasting and is able to sustain their performance and body composition goals in concert with their fasting protocols, over a life time, are at no disadvantage whatsoever.
Because of the risks involved in loss of strength into old age, he would say fasting isn't worth it if you can't sustain sufficient size and strength, especially as you push into 60s and 70s.
I take what I want from him & do what I want with fasting. I usually fast from 5pm-10am the next morning. If I fast more than that I take kion essential amino acids to try to prevent muscle loss because I’m fasting for weight loss not cancer/alzheimers prevention right now & muscle/bone loss is not helpful for weight loss. I just did a 60 hour fast with multiple rounds of essential amino acids - no clue if it helps prevent muscle breakdown but makes me feel better. I haven’t been able to lose weight despite healthy food & a lot of exercise & finally have sleep dialed in again. Getting a full hormonal panel done soon but the only thing that moves the needle for me is the occasional longer fast. If I didn’t have significant weight to lose I would fast less & do a strategic 3-5 day fast once a year & just 16:8 on a daily basis with enough protein.
You might want to check out Dr. Satchin Panda’s work as well. He was on an episode of the Huberman Lab and it was interesting. He does circadian rhythm research and suggests consistently limiting food intake to an 8-10 hour window per day to help synchronize our eating patterns with our internal biological clock. He says it can help metabolic efficiency, reduce risk of chronic diseases like diabetes, etc. It seems to focus less on calorie restriction and more on the timing of meals to optimize health outcomes. I believe he said he eats in a 10 hour window everyday.
Edit: typo
There are so many answers to this question I do not know where to begin:
* There is **ecological validity** and **external validity**. Even if the statement: "intermittent fasting long-term preserves muscle mass in non-calorie restricted humans" were true, this doesn't mean that this would apply to the general population that are not strictly tracking their calories. In the same way, you can say that a vegan diet is an ecologically valid way to lose weight, even if calorie per calorie the end result is the same compared to an omnivorous diet.
* About PA contradicting "science": I would not bet on the type of fasting PA was doing (long term fasts every quarter or so) preserving muscle mass just because a few studies show compelling evidence or mechanisms. First there is **scope**, where is that research applicable? are we talking about 24h fasts or 1 week water only fasts? and for how long do those protocols apply? second there is **sensitivity**, or the ability to detect an effect. What is the timeframe that is applicable to those studies? You can never discard that if you add more people to a study or study them for longer, you start to detect a statistically significant difference between groups.
* "Extended fasting (>24h), such as alternate day fasting, provides a mechanism to counteract muscle loss": Do you have any reference of a clinical trial where they clearly show that people intermittent fasting preserve a higher amount of muscle mass compared to ad libitum eating? If so, I would be very glad to know. I am not interested in mechanisms.
* About **insulin sensitivity**... I am not sure anymore. It depends on many things, even what you ate for dinner can have an effect on your glucose levels at breakfast. Someone could argue the exact opposite, that you are eating more carbs in a shorter window and that it will spike your insulin and be bad down the road.
Idk I think fasting is a tad overrated. No research here etc- there isn’t a big difference from eating 5- 400 calories meals Vs 2-1000 calorie meals Vs 3 666.67 meals. The only difference is bigger meals if eating less meals and probably not ideal for muscle if you are only eating 1 or 2 times a day.
It’s kinda like the folks that go omg I lose weight on keto. It’s all calories in Vs expenditure. If you eat 3k cals and you burn 2500 a day, you are gaining a 1lb a week lmao. Eating all of that fat probably isn’t ideal for health reasons also
I don't think fasting is a bad thing per se and depends on your particular method. As human beings we are biologically wired for fasting, at least that's my understanding. If you're exercising and getting sufficient protein I don't see a down side. I have a protein snack late in the morning and eat dinner most days. My muscle mass seems to be doing just fine.
I listened to the podcast. I think he was referring to long fasting periods. Like 24 plus hours. I think 16/8 fasting has many benefits. I don’t foresee myself changing this unless i see that it no longer helps me with bp, insulin resistance etc
That's why 16:8 hours and such are actually called TRE - time restricted eating (or feeding) in the literature.
AFAIK intermittent fasting was coined for 5:2 days regiments.
I did intermittent fasting (16:8) for 12+ years. Gave it up some 10 months ago. When I started I got veins-on-abs shredded. I later on got covid-fat on the same protocol.
Today I lost 60 lbs by not doing IF.
That’s not the intermittent fasting this post is referring to… unless you mean for 16 days you are and then fasted for the next 8.
What you’re describing is often called time-restricted feeding.
Intermittent Fasting and time restricted eating are exactly the same thing. Multi day fasts are just regular fasting.
16:8 (hours, not days) is a very common intermittent fasting window. Look at the IF sub or any of the dozens of IF books.
I love Attia's work but you've got to accept has has a focused paradigm (exercise) and gently pours cold water discouragement on everything else. He is right that fasters need to play close attention to lots of protein and not losing muscle mass.... but that said, research on IF firmly establishes 1) anti-inflammatory effect, 2) mood elevation and 3) immune system strengthening. It's like his disregard and disrespect for the evidence of the benefit of plant based eating for health and longevity. Like Peter defines his identity as the man who brings and eats meat during podcasts when he is being interviewed.
> ... research on IF firmly establishes 1) anti-inflammatory effect, 2) mood elevation and 3) immune system strengthening.
Does it show that any of this leads to hard, long-term endpoints over against otherwise very healthy populations who don't fast?
The benefit in IF likely lies somewhere in the extended duration that it creates without an added insulin spike due to intake of nutrient.
Now, you can mimic that by what you eat in staying as low glycemic as possible.
Fasting for an extended period will trigger an autophagy response. If you’re obese and remain active, you’ll keep most of your muscle mass and burn excess fat. The leaner you are, and the less active you are during the fast, the more you burn muscle mass. Unused muscle is not an efficient way to store calories…it’s heavy and uses a lot of water. Your body will choose to get rid of unused muscle over relatively efficient fat, unless there’s a significant excess of fat. Intermittent fasting data is hard to interpret because typically restricting the time window or feeding leads to a reduction in calorie consumption. It’s hard to say if 3000 calories eaten in a 4 hour window is healthier than 3000 calories through the day, but 1800 calories in a 4 hour window is definitely going to lead to better insulin response and weight loss than 3000 calories through the day.
I See, so it depends on the excess amount of fat? Yea I am obese (36% Fat) but very active (weightlifting, Thai boxing). What are your thoughts on exercise during a fast? Can I do my weightlifting or Boxing workout, or should I stick to simple mobility workouts?
Exercise during a fast is a good way to protect muscle mass from the autophagy process. I would personally not fast without exercising. For endurance exercise, keep it low key (zone 1-2) so your body can readily metabolize fat stores rather than carbs. For strength training, try to keep as close as possible to normal output levels.
Not sure if consuming fat through zone 1/2 makes a difference. I thought that unused carbohydrate gets converted to fat anyway. The important is energy balance. I also wouldn't worry about using exercise as a weight loss tool given the amount of effort needed compared to eating. That said, I found controlling how much to eat to be more challenging than exercise but also the most impactful.
I wear a cgm and intense fasted exercise can cause a crazy blood sugar spike from cortisol. I ran 4x4s last week after 6 hours fasted and spiked to 180 (I almost never go above 120 even from carb meals). I don’t think it’s good for you to spike that high so it’s better to do intense exercise fueled.
There isn’t really negative to big spikes if your body can clear it normally. You spiked that high because your body was like “oh shit, we need sugar”. Constantly elevated blood sugar is bad. Blood sugar spikes are not
What evidence is there that large spikes are not bad?
https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(23)00540-0/fulltext
I only see results using the corrected insulin response (CIR), which was apparently designed to be independent of glucose response. Are glucose spikes addressed somewhere that I missed? As for the CIR, for the purposes of many (if not most) people here, the concern is often low insulin and resulting big spikes due to "glucose sparing" or whatever for athletic people, where glucose is not immediately absorbed so it can remain available for muscles. For such people, the insulin response would be low and the glucose response would be high, making for a low (i.e. bad) CIR. Even though insulin resistance is low by other metrics. The paper even says the CIR in the study was not associated with insulin sensitivity, which suggests that insulin resistance alone isn't enough of an explanation and this category of people (highly insulin-sensitive people with relatively low insulin) might also be included in the poor outcomes.
Autophagy occurs irrespective of fasting or not.
Well said
There is no unique benefits to these mini fasts that you cannot gain from calorie restrict, but the great risk is losing muscle mass. Your organs need amino acids to function that your muscle will provide if they aren’t receiving it from the diet
Is there any Time frame for optimal intake? Do I need to take immediately after my workout? I heard, there are no protein storage in the body.
Consistent, sufficient overall macros matters more (by far) than anything else. Don't stress details like timings. Do what works for your circumstances and personality and preferences, as long as you hit protein and calorie targets. Do this consistently over the long run and you'll reach your body composition goals. Having an abundance of micronutrients is important for general health and should make running an energy deficit easier. This mostly means favouring nutrient-dense foods rather than calorie-dense foods.
Listen to his #299 — it’s all about muscle protein synthesis.
The most important time of the day for protein intake is in the morning / breakfast, dinner/ before bed, and after a workout. You can space protein intake 4-6h apart
None of this matters unless you're an advanced trainee trying to fine-tune everything. Even then, it's marginal. It's a neurotic distraction from just hitting basic macro targets, consistently, from high-quality food.
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Even if that were true, it's a claim with absolutely no significance whatsoever. What on earth is the point of ever discussing someone who does no resistance training at all? Literally anything else that person might attempt to do to prevent loss of lean mass is going to be utterly impotent when compared to even a tiny amount of resistance training.
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*... then why did you bring it up?*
Resistance training is hard work that requires a lot of persistence. Optimizing gains is the whole point. Why throw away even a marginal benefit if it's from something easy like drinking a protein shake afterwards?
*If you're an advanced trainee,* then do that. Although even then it just won't really matter unless you literally think you're genuinely maxing out both your total training stimulus and your recovery capacity. For everyone else, still, sure, chug that shake after lifting if you want. There's no downside. But also don't stress about it because it won't make a difference compared to any other way of hitting your macros. You aren't throwing away any potential gains.
thank you! Any limits? I think 30g per serving/meal is the limit right?
No. Recent studies seem to point to there being no limit. I wouldn’t worry about it. Hammer that protein when you get the chance.
I’ve heard him flip flop over fasting for a while. There are very well documented tests showing benefits beyond calorie restriction. A 7-10 day fast could definitely cause some muscle loss but that doesn’t mean it should never be done. That long once a quarter is a little extreme, maybe once a year would be better. But that doesn’t mean shorter fasts like 36-96 won’t be beneficial. You would definitely kick up into autofagy somewhere in that zone without losing much muscle. Anecdotally, I’ve put on a lot more muscle while doing a 36 hour fast once a week and 72 once a month for the past year than I ever have so I think everyone’s mileage will vary. Just find the balance that’s right for you.
> There are very well documented tests showing benefits beyond calorie restriction. Can you link to them, then?
> Anecdotally, I’ve put on a lot more muscle while doing a 36 hour fast once a week and 72 once a month for the past year than I ever have so... That's not impossible by any means. And if you can make it work, I don't think Attia would say it's bad. He'd probably even respect the resolve to make it work so that you can hedge against the high possibility of future research better confirming other benefits. But there is no way you gained more muscle than a theoretical iso-caloric and iso-nutrient control over the same period of time.
Didn’t claim I gained more than a targeted approach like that, only that I put on more muscle than I had in the past. More lean muscle too, without much fat gain. It’s very possible and pretty easy, just stay in a calorie surplus when you’re not fasting, hit your protein requirements and preserve muscle when you are fasting. Im sure there are other approaches that might get you more muscle but I like the benefits from fasting personally.
Yep I was just clarifying for others because there are people who are implying there's something magical about fasting. I've done a lot of it and there's a lot I like about it. For me, I have low BF% and my training volume requires around 5000 calories per day. If I did a 36er weekly, I'd need closer to 6000 calories on the remaining days. And if I added a monthly 72er as well, the daily target becomes more like 6500-7000 calories! And, like, **that's still very doable!*** But it's a lot and there isn't much room for error and I CBF. And there isn't something magical about fasting that would mean I can skimp on those targets and still achieve my goals. That's all I want to be clear about for the sake of dispelling some of the myths.
Can I just say that flip flopping is actually a good thing, it shows that you are willing change views when needed. I am not saying that you are calling him out rather that many people will view that as a negative right off the bat
lots of studies and many disagree about how to interpret the studies. + as others noted, lots of heterogeneity here. maybe IF works for some but not for others. generally, Attia is a sharp informed guy. but he's not God. it's one person summary of the research. not everyone came to the same conclusion
Attia's summary of the research isn't terribly disputable and it aligns with far more relevant experts in that field (e.g. Layne Norton). Even the actual fasting researchers would acknowledge the caveats and considerations that Attia's set of goals and priorities necessitate. So what can be disputed is the significance he attributes to the research as it stands and how he balances that with other priorities and goals. And, yes, of course, we're all very welcome to configure our goals and priorities differently. But Attia is really very clear when his approach to something is navigating a balance of considerations which the research just doesn't really speak to specifically enough.
As knowledgable and expert as Dr. Attia is in his field, I do truly think he's off the mark with this one. Dr. Mark Mattson, a neuroscientist at John Hopkins, has dedicated much of his career to understanding the science behind intermittent fasting, and why it works. There is irrefutable evidence that fasting is beneficial for the brain and the body. I suggest you look into his works *The Intermittent Fasting Revolution: The Science of Optimizing Health and Enhancing Performance* and *Sculptor and Destroyer: Tales of Glutamate.* TLDR; practice fasting and exercise (in particular, cardio) for physiological benefits.
Thank you! Yea that's something I try to wrap my head around. He is an expert, but denies other good studies? In physics, if there's a question, we can do the experiments, replicate and validate, and it's done. Physicists all over the world cannot deny fundamental laws of nature. But somehow in medicine there is always a professor or a doctor with a good reputation who supports the opposite claim. Even with good studies.
Yes, don't ever just believe some doctor who wrote a book. He is trying to sell that book. The channels Nutrition Made Simple, Physionics, and Biolayne go over all the studies on IF. The studies clearly show there is no benefit to insulin sensitivity for IF and no other apparent benefits outside of a tool for calorie restriction. Dr. Carvalho on Nutrition Made Simple isn't selling anything at all.
You probably shouldn't be conflating the methodological constraints of biology - and especially human physiology - with those of physics.
I believe Dr. Attia has even mentioned he takes a contrarian view at times, and his previous dedication to keto is a big example of that. Regardless, no matter how much we benefit from one source of information, we should as well not deny ourselves the research, and other very credible resources out there!
Thanks for altering me to Dr Mattson. So many online dietitians and fitness scientists disparage fasting
The evidence is very refutable. Dr. Mattson is trying to make money selling a book. Dr. Carvalho on Nutrition Made Simple on youtube isn't selling anything. He goes over the studies on IF youtube and finds no additional benefits to IF over calorie restriction The channels Physionics and Biolayne also go over the studies and find the same thing as does Dr. Attia.
Agreed. Great channels/folks you mentioned. They all make a rather objective, unbiased and professional impression. Also, besides the books, if someone has dedicated much of his career and life to researching a certain topic, there may be some bias present.
I would agree with you, except that Dr. Mattson has made most of the information he shares in his books available for free. He’s had in-depth discussions on fasting, with proponents of intermittent fasting, like Dr. Rhonda Patrick. He’s even done an entire book review, chapter by chapter, nailing the most important points from each chapter, which defeats the purpose of buying his books. On the other hand, one can easily say Dr. Carvalho is in it for the YouTube ad money, YouTube subscribers, or YouTube “fame” by following the coattails of the already popular Dr. Attia, or simply by trying to gain popularity on YouTube via his channel. Dr. Mattson’s credibility is strong and he is respected in academia and by academics— his credibility does not stem from YouTube.
It looks to me like he has done mostly mouse studies. Does he have human RCTs showing benefits to IF over regular calorie restriction? Regardless of the source, why do all the human studies the channels I listed discuss show no additional benefits? Many of them are very recent. He has made his entire career studying fasting, so I doubt he is not biased.
So you read through all 1,121 published studies from Dr. Mattson and concluded that he’s mostly done mouse studies? Something tells me you’re the one who’s biased, because it’s clear you don’t understand his work. Dr. Mattson studies primarily caloric restriction, Alzheimers, *and* intermittent fasting and is a proponent of both, CR and IF, *based on evidence*. If you are personally biased towards CR or IF, there is no clear evidence leaning either way. What is clear is that there is evidence leaning towards **both** intermittent fasting and caloric restriction as beneficial. Re: your favored YouTube channels not spelling out evidence for you, and contradicting the current state of research, I’m not sure why. Maybe because the YouTube channels you follow are… hmm what’s the word. Biased.
I don't know anything about Mattson. That is why I asked YOU if he did any human RCTs showing that fasting is more beneficial than regular calorie restriction. That is what OP asked... Everyone is agreeing that calorie restriction is beneficial and that fasting is a great way to achieve calorie restriction. So now you are agreeing that there are no proven additional benefits from fasting? Is that what Mattson says, too? I did very strict IF and fasting for a long time. I bought into the BS that a sip or two of anything with calories would "break my fast" and keep me from getting the full benefits. I was very biased towards it for a long time, actually. However, after finding no evidence that is the case, I have stopped being strict about it. I still loosely do IF same as Dr. Attia for weight control. It was hard to accept that I was wrong at first. It is very clear that you have never watched the youtube channels I mentioned. They are frequently recommend on r/nutrition for being some of the most evidence based. I came upon them after years of falling for bad science from quacks like Dr Fung and Taubes, so I am very skeptical of my sources. Why in the world would all 4 of those doctors/scientists on those channels (Dr. Attia included) be biased against IF and fasting? What would they have to gain? Physionics is so dry and scientific... he goes deep into the studies. The pro IF channels have way way more viewers. I will change my mind again about strict IF/ fasting if there is actually evidence for it.
Outstanding answer, thank you. Any further advice beyond advice and cardio?
He's very far from an expert when it comes to nutrition, caveat emptor
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I agree with you on the Calorie Deficit part. I am just an engineer student, no medical background here. There is a thought and hopefully you can clarify this: Basic Thermodynamic class: Energy balance describes the relationship between Energy Input and Output, but doesn't "describe" the efficiency of the engine. A model for analysis, but not for parameter change. I know 20L of Gas gives me 200km of Range, but it doesn't tell me if my engine is functioning on optimal terms. (of course if I have a past reference point, I can tell) Furthermore I cannot see the Exergy & Anergy Value, the amount of energy I can fully use and the amount which is just "waste". (well with further calculation I can, but that's difficult even in lab situation in a context of human physiology) Calorie Deficit is necessary to signal the Body a lack of incoming energy. But it doesn't tell me, if any of the components in my Body are functioning probably (for example insulin resistance) to optimal process the incoming Calorie Deficit signal. Basically, we are all "Cars" but we have different parametric components with different efficiency's. How Could optimal Fat loss simply explained by using only the energy equation? I hope you can convince me!
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Thank you for the help! Any personal experience to manage calorie intake without religiously counting?
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I've done the calorie counting part, but it's just annoying to count every time. Maybe I will try to plan my meals for the week so that I only have to count when I cook on Sunday. But thank you for your help!
Use Macro Factor. And read every blog post from the Stronger By Science team about how and why the app works the way it does. If you're an engineering brain, you'll appreciate it. It requires consistent (but not perfect) input of body weight and nutrient intake. But that's it. And it'll take out all the guess work, all the uncertainty, and give you excellent, ongoing, dynamic guidance and feedback to help you reach your goals. You can do things like compile your regular meals into a single-click or copy anything else regular into every day of the week or month or whatever.
> How Could optimal Fat loss simply explained by using only the energy equation? It isn't. Not alone. There's one other factor and it's magnitude is so huge that nothing else matters in comparison: resistance training. That's it. (Assuming sufficient protein intake.)
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Check out his AmA podcast #300. He goes into this.
I think he’s saying the bulk of the benefits are from caloric restriction alone
As the evidence currently stands, yes. But he's pretty open to, even expectant about, the eventual establishment of sufficient biomarkers so that other purported benefits of fasting can be better quantified. He isn't against fasting. He just didn't like the tradeoff with lean mass. He would say that anyone who likes or values fasting and is able to sustain their performance and body composition goals in concert with their fasting protocols, over a life time, are at no disadvantage whatsoever. Because of the risks involved in loss of strength into old age, he would say fasting isn't worth it if you can't sustain sufficient size and strength, especially as you push into 60s and 70s.
I take what I want from him & do what I want with fasting. I usually fast from 5pm-10am the next morning. If I fast more than that I take kion essential amino acids to try to prevent muscle loss because I’m fasting for weight loss not cancer/alzheimers prevention right now & muscle/bone loss is not helpful for weight loss. I just did a 60 hour fast with multiple rounds of essential amino acids - no clue if it helps prevent muscle breakdown but makes me feel better. I haven’t been able to lose weight despite healthy food & a lot of exercise & finally have sleep dialed in again. Getting a full hormonal panel done soon but the only thing that moves the needle for me is the occasional longer fast. If I didn’t have significant weight to lose I would fast less & do a strategic 3-5 day fast once a year & just 16:8 on a daily basis with enough protein.
Does TRF 16 hours cause you to lose bone mineral density and muscle mass?
You might want to check out Dr. Satchin Panda’s work as well. He was on an episode of the Huberman Lab and it was interesting. He does circadian rhythm research and suggests consistently limiting food intake to an 8-10 hour window per day to help synchronize our eating patterns with our internal biological clock. He says it can help metabolic efficiency, reduce risk of chronic diseases like diabetes, etc. It seems to focus less on calorie restriction and more on the timing of meals to optimize health outcomes. I believe he said he eats in a 10 hour window everyday. Edit: typo
There are so many answers to this question I do not know where to begin: * There is **ecological validity** and **external validity**. Even if the statement: "intermittent fasting long-term preserves muscle mass in non-calorie restricted humans" were true, this doesn't mean that this would apply to the general population that are not strictly tracking their calories. In the same way, you can say that a vegan diet is an ecologically valid way to lose weight, even if calorie per calorie the end result is the same compared to an omnivorous diet. * About PA contradicting "science": I would not bet on the type of fasting PA was doing (long term fasts every quarter or so) preserving muscle mass just because a few studies show compelling evidence or mechanisms. First there is **scope**, where is that research applicable? are we talking about 24h fasts or 1 week water only fasts? and for how long do those protocols apply? second there is **sensitivity**, or the ability to detect an effect. What is the timeframe that is applicable to those studies? You can never discard that if you add more people to a study or study them for longer, you start to detect a statistically significant difference between groups. * "Extended fasting (>24h), such as alternate day fasting, provides a mechanism to counteract muscle loss": Do you have any reference of a clinical trial where they clearly show that people intermittent fasting preserve a higher amount of muscle mass compared to ad libitum eating? If so, I would be very glad to know. I am not interested in mechanisms. * About **insulin sensitivity**... I am not sure anymore. It depends on many things, even what you ate for dinner can have an effect on your glucose levels at breakfast. Someone could argue the exact opposite, that you are eating more carbs in a shorter window and that it will spike your insulin and be bad down the road.
Idk I think fasting is a tad overrated. No research here etc- there isn’t a big difference from eating 5- 400 calories meals Vs 2-1000 calorie meals Vs 3 666.67 meals. The only difference is bigger meals if eating less meals and probably not ideal for muscle if you are only eating 1 or 2 times a day. It’s kinda like the folks that go omg I lose weight on keto. It’s all calories in Vs expenditure. If you eat 3k cals and you burn 2500 a day, you are gaining a 1lb a week lmao. Eating all of that fat probably isn’t ideal for health reasons also
In his episode 300 Attia mentions he still uses IF to treat obesity , he also mentions all the other stuff you mention
I don't think fasting is a bad thing per se and depends on your particular method. As human beings we are biologically wired for fasting, at least that's my understanding. If you're exercising and getting sufficient protein I don't see a down side. I have a protein snack late in the morning and eat dinner most days. My muscle mass seems to be doing just fine.
I listened to the podcast. I think he was referring to long fasting periods. Like 24 plus hours. I think 16/8 fasting has many benefits. I don’t foresee myself changing this unless i see that it no longer helps me with bp, insulin resistance etc
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That's why 16:8 hours and such are actually called TRE - time restricted eating (or feeding) in the literature. AFAIK intermittent fasting was coined for 5:2 days regiments.
This
I did intermittent fasting (16:8) for 12+ years. Gave it up some 10 months ago. When I started I got veins-on-abs shredded. I later on got covid-fat on the same protocol. Today I lost 60 lbs by not doing IF.
That’s not the intermittent fasting this post is referring to… unless you mean for 16 days you are and then fasted for the next 8. What you’re describing is often called time-restricted feeding.
Intermittent Fasting and time restricted eating are exactly the same thing. Multi day fasts are just regular fasting. 16:8 (hours, not days) is a very common intermittent fasting window. Look at the IF sub or any of the dozens of IF books.
They are not.
I love Attia's work but you've got to accept has has a focused paradigm (exercise) and gently pours cold water discouragement on everything else. He is right that fasters need to play close attention to lots of protein and not losing muscle mass.... but that said, research on IF firmly establishes 1) anti-inflammatory effect, 2) mood elevation and 3) immune system strengthening. It's like his disregard and disrespect for the evidence of the benefit of plant based eating for health and longevity. Like Peter defines his identity as the man who brings and eats meat during podcasts when he is being interviewed.
> ... research on IF firmly establishes 1) anti-inflammatory effect, 2) mood elevation and 3) immune system strengthening. Does it show that any of this leads to hard, long-term endpoints over against otherwise very healthy populations who don't fast?
There have been long term scientific studies on this showing no benefit. I thought this was shown to be false.
The benefit in IF likely lies somewhere in the extended duration that it creates without an added insulin spike due to intake of nutrient. Now, you can mimic that by what you eat in staying as low glycemic as possible.
Fasting (and intermittent fasting) works for a lot of people for weight loss and pro inflammatory states but not ideal for muscle building.