#89 - AMA #11： All things fasting
Episode Stats
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Summary
In this episode, Dr. Peter Atiyah is joined by Dr. Bob Kaplan to discuss what fasting is, what it is not, and why it's important to know the difference between it and alternate day fasting.
Transcript
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Hey everyone, welcome to a sneak peek, ask me anything or AMA episode of the drive podcast.
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I'm your host, Peter Atiyah. At the end of this short episode, I'll explain how you can
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access the AMA episodes in full, along with a ton of other membership benefits we've created,
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or you can learn more now by going to peteratiyahmd.com forward slash subscribe.
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So without further delay, here's today's sneak peek of the ask me anything episode.
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Welcome to a special AMA episode focusing on my recent seven day fast, in addition to a deep dive
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on fasting in general. As this is a topic we get so many questions on, we figured dedicating an entire
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AMA to it would be of value. So we hope you enjoy. I'm once again joined by my head of research,
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Bob Kaplan. So without further delay, here's today's special AMA focusing on fasting.
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Hello and welcome to a fasting edition of ask Peter anything. Peter, how you doing?
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Doing all right. And this is Bob Kaplan. So let's just jump right into the questions around fasting.
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You obviously get a lot of questions on fasting. And I thought before we get into fasting,
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maybe you could discuss what fasting is, a definition of fasting. So we get a lot of questions
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around what is IF, what is TRF, what is ADF, what's a fasting mimicking diet, and what is prolonged
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fasting, even what's an overnight fast. So I can remind you of all those. Okay. Why don't you give
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them to me one at a time? Okay. So I think maybe the first one is overnight fast. When somebody
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refers to an overnight fast, what is that? So that, as its name suggests, is sort of the standard fast
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that almost by definition, everybody does between dinner and breakfast. So if you finished dinner at
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seven o'clock in the evening rather, and you had breakfast at seven o'clock the next morning,
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you would have just undergone a 12 hour overnight fast. Okay. And TRF, time restricted feeding,
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some people call it TRE, time restricted eating. That is an idea where you increase that window
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from just an overnight fast into a slightly longer window. So if the overnight fast that I used a moment
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ago were to be put into time restricted feeding nomenclature, you would call it a 12-12, meaning 12
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hours of fasting followed by a 12 hour window, say 7am to 7pm in which one would eat. You can extend
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that and you could say a 14-10 window or a 16-8 window or an 18-6 window where the first number
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generally refers to the period of time that has no nutrient exposure and then followed by the
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window and time in which one would be able to consume food, typically ad libitum, meaning without
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restriction. Okay. So rolling into the next one, alternate day fasting. So again, as the name suggests,
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alternate day fasting is when every other day a person does something other than their traditional
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ad libitum eating. Now, the most strict way that one could do an alternate day fast, which would be
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quite difficult to do over the long haul, would be to literally consume nothing every other day.
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More commonly when people do alternate day fasting, they have a hypocaloric day. So they might on
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alternate days consume say 1,000 calories and on the non-fasting day they would consume whatever
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they consume ad libitum and that might be say 2,500 to 3,000 calories.
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So I know that you're somewhat of a stickler on the definition. So in that case, it's almost like
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alternate day calorie restriction on the opposite day. Yeah. One way that I think about that,
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actually a couple of ways that I think about it is if you're looking at a calendar for a strict
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alternate day fast, if you're going to start it in January, January 1, let's say you're going to
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eat in January 2nd, you're going to fast. You can mark off every even day of that month and you know
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that you're fasting on that day. And then on the alternate days, you're eating. And I sometimes
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think about it in terms of when you talked about TRF or time-restricted feeding or time-restricted
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eating, you think about it in the context of a 24-hour clock. With alternate day fasting,
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it's almost like a 48-hour clock on the alternate days. And I think it can vary quite a bit on your
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feeding days that you might do a one meal a day, which would be almost like a 47-1.
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One hour of the day you're feeding and then the 47 hours you're not. I don't suspect that people
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are eating between midnight and 11.59 on the feeding days. So there's probably a bigger window
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than just 24 hours when you think of an alternate day fast.
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So this is a term that unfortunately has gained a lot of popularity. I guess I say unfortunately,
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because I don't find it to be that helpful. I think what people generally mean when they say
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intermittent fasting is time-restricted feeding. And in the end, who cares what people say? As long
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as they know what they're talking about and know what they're referring to. But I personally don't
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find the term intermittent fasting to be very accurate because I don't think that not eating for
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16 hours really constitutes a fast per se. And that's why I do prefer the terminology time-restricted
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feeding or time-restricted eating to describe the extension of the overnight fast. I think if you
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were going to give a true meaning to the word intermittent fasting, you would describe that
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sort of the way I'd describe periodic fasting, which is at some frequency, you actually undergo a fast.
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And that might mean every month or every quarter or every six months or every year,
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you undergo a fast that is intermittent. And again, that gets into probably another one of
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the definitions you're going to ask about, which is what does fasting mean? Does fasting
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necessitate a complete elimination of calories or could it also be done through reduced calories?
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Yeah. Maybe one other bucket, a popular diet is the 5-2 fast,
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which is instead of looking at a 24-hour window or a 48-hour window, you're looking at the calendar
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week and you're selecting a couple of days where it's actually, I think it's calorie restricted,
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like you said, with the alternate day fasting. So on the two days, so eating five days out of the
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seven-day week, you're eating normally two days out of the seven-day week. I'm not sure if you can pick
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them, whatever days you want to pick them. The usual version of that protocol is that they are not
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successive, but otherwise it's sort of up to you. Okay. Yeah. And in that case,
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it'll be typically a hypocaloric 400 to 600 calories, I think on your quote unquote fasting
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days. Yep. Fasting mimicking. What is mimicking fasting?
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Well, I think the term fast mimicking diet or fasting mimicking diet, FMD is actually a trademark
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that belongs to a company that sells a product that is a pre-packaged five-day fast. I believe the
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company is called El Nutera and it's based on the work of a guy by the name of Walter Longo. And it
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has a very clear prescription around its macronutrients and its total caloric balance. So in other words,
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to be very clear, the term fast mimicking diet is to that what the term Kleenex is to the actual tissue
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that is branded Kleenex. So there are an infinite number of tissues that you can blow your nose into.
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There's only one Kleenex. There are an infinite number of ways that one can do a reduced calorie
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fast that approximates some of the metabolic benefits of fasting, but there is only one
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fast mimicking diet or FMD. For what it's worth, that's approximately 900 to a thousand calories on the
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first day. And I believe it's approximately 700 to 750 calories for days two through five. But I could
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be off a little bit on that. Okay. And then last but not least, prolonged fasting or multiple day
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fasting. So again, if we're now talking about absolute fasting as opposed to reduced calorie fasting of
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which fast mimicking diets are a subset. So again, a reduced calorie fast would be typically from a
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clinical perspective, using our patients as an example, we do anywhere from three to seven days,
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typically at about 500 to 700 calories a day. We also have very different macros that we prescribe
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than some of the commercial applications. But again, we call that a reduced calorie fast.
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So then what you're talking about, of course, it's the simplest one to explain, actually. It's just
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water only. And I say water also includes tea and some minerals, but it's no calories for a period of
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time. And again, it's typically done for three to seven days at a time. I can't believe I'm going to
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give you the what abouts. So what about coffee? Coffee and tea and water or just tea and water? Is there
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a difference? There probably is, but again, it probably isn't as much of an issue as people want to make it
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out to be. When we have patients who are quite caffeine dependent, we don't like to see them
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eliminate caffeine during a fast because fasting can be challenging enough on its own. And I don't
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really think it benefits someone to also go through caffeine withdrawal during that period of fasting.
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So I'm sort of fortunate in this regard in that I drink coffee every day, but I don't seem to have
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any dependency on it. So when I fast, I don't drink coffee, at least for the first five days. Sometimes
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as a treat on days five, six, seven on those longer fasts, I'll drink a black coffee. Some observers have
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suggested that enhances autophagy late enough in a fast. I'm not necessarily convinced that that's the
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case. And truthfully, I think I do it just to sort of break up the board. A black coffee has never tasted
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so good as it does on day five of a water only fast. But for most of the time, I don't consume
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coffee, even black during a fast. And again, we make that decision very clinically with a patient.
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There are some patients in whom a big part of the fasting protocol is gut rest. And in those patients,
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we definitely want to avoid coffee, not so much for the caffeine, but more for some of the other
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phytochemicals that are in it. Tea seems to be a little bit more forgiving. And obviously there's
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plenty of caffeine in enough types of tea. So again, the caffeine is probably less the issue.
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But I do think that for most patients, the sort of bread and butter, no pun intended,
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of a fast is water. And that can be bubbly water, still water. You know, bubbly water is a nice way
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to sort of mix it up. And as you know, I have a particular brand of bubbly water that I fancy the
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most. So I go through those at a geometric rate during my fasting weeks. Okay. So obviously you alluded to
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the next question, which is, well, at least one of the types. So what type of fasting do you personally
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engage in and why? So why do you fast and what types of fasts? Of all those fasts we just talked
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about, TRF, ADF, IF, FMD, and the prolonged fast, which ones are you engaging in and why?
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