The 3 Levers of Fasting [Peter Attia]

Always pull one, sometimes pull two, never pull none.

Listen to the Tim Ferriss Show:


I think that one thing that I absolutely learned through fasting is the enormous importance of strength training throughout a fast. You’re going to lose muscle mass when you fast, you have to accept that. So the question is how do you minimize that damage? How do you lose as little muscle mass as possible? And strength training daily during a fast has become an important part of that. But when you look at time-restricted feeding, or people call it intermittent fasting, although I don’t like that term very much. I think time-restricted makes more sense when you’re just talking about 16 or 18 hours. I’m really starting to see a lot of people who do that excessively and who aren’t necessarily training correctly. They lose weight, but they’re losing muscle more than they would want to see.

And we just had a patient who we did a DEXA scan on last week and it was probably the first one we’ve done in 18 months on him. And in that 18 month period, his body weight had not changed. Maybe he was a bit lighter, actually, he might’ve lost four pounds. But his body fat was so high I almost fell off my chair and he doesn’t look chubby, but it speaks how much muscle he’s lost. So his body fat went from about 18 percent to 30 percent.

Tim Ferriss: Yikes.

Peter Attia: It’s just a totally unacceptable amount of fat for someone his age. And his visceral fat went up, which I actually care more about than body fat. We can talk about that later, but his visceral fat also went up. So, this is a guy who has religiously been doing his time-restricted feeding every day, but he doesn’t really lift weights.

He walks and does some yoga and stuff like that, but he’s not doing strength training. So I think in a person like that, there’s a real downside to too much time-restricted feeding. And even for myself, in the last four or five months, I did a DEXA back in January and I hadn’t done one in years. And from January to the last period that I had done a DEXA, my body weight was almost identical. Maybe I was two pounds lighter this year versus the last time. But my body fat was up.

I think I went from 10 to 16 percent body fat. And again, you could say, “Well, 16 is not the end of the world,” but that was a significant loss of muscle and gain of fat. And I did wonder if that was just too much, because I always exercise in the morning, but then don’t eat. So to exercise, and especially when you’re strength training, to provide yourself with any amino acids every single day to undergo muscle protein synthesis, I think is a little bit risky. So I’ve been looking at other strategies around that. So for example, front-loading the meals.

Tim Ferriss: Quick question, and then we’ll come back to front-loading meals. During that period of time, were you doing, and I may be misremembering, one three-day fast a month or one week-long fast every quarter? What was the frequency of — 

Peter Attia: All of the above. Yeah, I probably spent maybe two years doing seven days a quarter, maybe a year doing three days a month. But in between it’s also doing lots of time-restricted. And honestly, I think the daily time-restricted was a bit more the issue because I think the three-day fast a month with a lot of lifting, I didn’t sense I lost a lot of muscle during that period of time, but I think every day, exercising in the morning, not putting calories in until later in the day, it has to be taken in the context of an individual. So if you’re someone who’s 100 pounds overweight or you have diabetes, it’s a totally worthwhile trade-off to lose muscle mass because you’re losing more fat mass along the way. So you are going to technically get leaner with that approach, but when you take a relatively healthy and lean individual, one has to be a little bit careful and look for alternative ways to get the benefits of that fast.

Tim Ferriss: So you were saying something about front-loading meals.

Peter Attia: Yeah. So I just find nowadays, although probably not tonight.

Tim Ferriss: Almost certainly not tonight.

Peter Attia: I’m going to eat a little bit more early in the day and a little less late in the day. So — 

Tim Ferriss: There may or may not be some mezcal involved.

Peter Attia: There will be.

Tim Ferriss: So we won’t take either of our Oura Ring data as the standard for this evening. I totally got caught up in my own fantasy narrative — 

Peter Attia: Fantasies about mezcal?

Tim Ferriss: So front-loading meals, could you just walk back and explain — 

Peter Attia: In an ideal world I think that the best way to do time-restricted eating would be to eat a big breakfast. So it would be to wake up, exercise, eat a huge breakfast. By huge I don’t mean gluttonous, but that’s your biggest meal of the day at say — I don’t know, let’s just put some numbers to it. You wake up at six, you work out from seven to 08:30, at nine o’clock you’re eating your largest meal. You eat another meal at one o’clock that is modest and you don’t eat again. That would be a great way to do 16 hours of not eating a day. That’s problematic for two reasons. The first is it’s socially problematic. It’s really easy to not have breakfast because very few people eat breakfast with other people, but dinner is our social meal. And for obvious reasons, it just poses a difficulty to be the guy who never eats dinner.

Tim Ferriss: Just as a side note, I’ve been at multiple dinners now, quite a few actually, where you’ve been fasting and we’ve all been sitting, drinking wine, and you just pass the cheesecake at the end and you take a big whiff and then continue moving it along. It’s entertaining, but it is pretty antisocial to be that guy.

Peter Attia: To be that guy drinking the soda water. And then the other thing is I think for many people it is hard to go to bed hungry and truthfully in a longer fast it gets easier because if you’re fasting for seven days, by the time you hit that fifth day, a lot of your hunger has dissipated, but 16 hours of not eating can generally pose some hunger and for some reason, I just think psychologically in the evening we’re a little less busy, so it’s even more noticeable. Whereas if you’re doing the traditional way that people think about not eating for 16 hours, it’s pretty easy to wrap yourself up and work in the morning, skip breakfast, and delay your lunch a little bit.

So I don’t know that I have a great answer for that other than I think people should be a little cautious and not just apply the same hammer to every nail and think about their own physiology a little bit and rely on these technologies like DEXA to make sure. Which again is so readily available, relatively inexpensive, and provides both good information about body composition and also this thing of visceral fat.

Tim Ferriss: We’ll come to the visceral fat in just a second. On the DEXA note, about — I don’t know, a year and a half or two years ago, I recall a conversation with a DEXA technician who said to me, “Over the last 12 months, I’ve seen many cases of people coming in who are newly avowed intermittent fasters who have had their body composition flip, basically.” Not necessarily flip, but they’ve had massive jumps in the percentage of body fat. And I put that on social as a note, not to say that all people who do time-restricted feeding experience this, and it was hilarious and also frustrating to see how many religious zealots there are around intermittent fasting who were just like, “Bite thy tongue.”

Peter Attia: Wait. But you said that according to this tech that they got better intermittent fasting or worse?

Tim Ferriss: No, they got worse.

Peter Attia: Oh, they got worse. So, it met with what I’m describing.

Tim Ferriss: It’s exactly compatible with what you’re saying, but there was a lot of resistance to the idea that would even be possible. Which I found really interesting, more social commentary than anything else.

Peter Attia: I think it just speaks to why I don’t like talking about nutrition very much because it does lend itself to politics, not literally, but it’s the politics/religion ethos, which is: whatever you’re eating is obviously the only thing. And I guess I just encourage people to be much more attuned to all of the tools. So caloric restriction, dietary restriction, time restriction, you’ve probably heard me go on and on about my framework, the three levers. Always pull one, sometimes pull two, occasionally pull three, never pull none. So time restriction, what we’re talking about, restricting when you eat, but otherwise not restricting how much or what. Dietary restriction is restricting some of the content in what you eat. So not eating carbs, not eating wheat, not eating meat.

Tim Ferriss: Not eating Doritos.

Peter Attia: Right. Not eating sugar. Those are all forms of dietary restriction. And then caloric restriction is restricting the amount. And so if you are never pulling one of those levers, which means you’re eating anything you want, any time, how much, whatever, that’s called the standard American diet.

Tim Ferriss: SAD.

Peter Attia: Yeah, the SAD. And we’ve been running a very good natural experiment on that for 50 years and the data are in. So it turns out that less than 20 percent of the population, probably less than 10 percent of the population, is genetically robust enough to tolerate the SAD. So, that’s a great piece of data. There are people out there who can eat KFC and Doritos and pizza any time they want and they’re generally okay to a first-order approximation. I would add that we don’t really know the answer to this question because we don’t have super granular data at the population level. But notwithstanding that, at least at the surface level, it appears that 10 percent of the population are largely immune to the SAD. But for the rest of the 90 percent of us schmucks, which I’m certainly in that camp, the SAD is lethal.

And so you’ve got to come up with a way to escape the gravitational pull of the SAD. And that’s why I think having these three levers at your disposal is the key. And yeah, I think that what happens is people get so into the camp of their lever, it’s all time restriction or it’s all dietary restriction, not too many people are in the all calorie restriction group. There’s a whole Calorie Restriction Society, and so there certainly are people that are in that camp, but it’s usually the first two camps that have the most zealots.

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