The benefits of fasting are myriad. And many of them are backed by research. But what’s more interesting than reading data from an experiment is hearing someone’s personal experience. Especially if that someone is a doctor. Peter Attia, a physician specializing in longevity, has been practicing intermittent fasting, or time-restricted feeding, for several years. Intermittent fasting is when an individual only eats during a certain window every day. The 16-8 regiment is the most common, whereby an individual won’t eat food for 16 hours (say 8 PM one day until 12 PM the next day) and will do all of their consuming during the remaining 8 hours (12 PM until 8PM). Peter Attia recently sat down with Joe Rogan to give his take on fasting based on both science and personal experience. I’ve transcribed a segment of the fascinating exchange.
Joe Rogan: With all that exercise that you do, I’m sure you have a voracious appetite.
Peter Attia: I mean, I do, but nothing like I used to. I fast pretty much every day.
Joe Rogan: Are you doing 16 hours–what are you doing?
Peter Attia: It depends. I split my time between New York and California. When I’m in New York, it’s absolutely one meal a deal, no ifs, ands, or buts, because the schedule is such that I’m seeing patients in the morning and afternoon, and I don’t want to waste time to eat.
Joe Rogan: What are you a doctor in?
Peter Attia: That’s a good question. I trained as a surgeon and did cancer surgery, but my practice is based on longevity. So it’s sort of, how do you apply nutrition, exercise, sleep, stress management, endocrinology, lipidology, supplements, hormones, all that stuff. Like how do you engineer how to make somebody live longer is my clinical interest. So in New York I eat one meal a day. It’s basically like a 22-hour fasting window and then I’m feeding within a 2-hour window. When I’m here, it’s about the same. Yesterday and today it’s the same. Today it’s been kind of a busy day–I won’t eat till dinner tonight. My short fast would be 16 hours. . .
You got to get in touch with your evolutionary self. I had this discussion with a friend this morning because he was saying to me that he can’t do 16 hours. . . You got to understand if our ancestors couldn’t function when they were hungry, we wouldn’t be here. So it’s not just that short-term adaptation to starvation is necessary–it’s probably beneficial, in other words, during these short period of deprivation to food, we get just a little bit more epinephrine and norepinephrine, we just get a little bit sharper, a little bit better. I can’t even remember what it was like to eat three meals a day, it’s been so long. . . I’ve been doing crazy s**t for 10 years nutrition-wise. I spent 3 years in ketosis, lots of fasting, but I think intermittent fasting or time-restricted feeding, probably at least 5 years.
Joe Rogan: For people listening, what are the benefits of that?
Peter Attia: If we’re going to get really technical, we have to be clear that I think a lot of the benefits are overstated, and a lot of the benefits are things that we have only studied in animals. There’s a guy named Satchin Panda at the Salk Institute in San Diego who is one of the world’s experts on time-restricted feeding. But, for example, a 16-hour fast in a mouse produces unbelievable results. If you take a group of certain types of mice or strains of rats or other rodents and in a 24-hour period deprive them of any nutrient for 16 hours, but then for 8 hours let them eat whatever the h*ll they want, they can’t gain weight. And the reason we think is that once you give a long enough period of time when the animal can ramp up the enzymes in the liver that are responsible for fat oxidation, they just basically become fat burning machines–I hate the term fat burning machine, it’s so overused–they basically just become unbelievably efficient at metabolizing fat. We have to be careful when we extrapolate that because you and I have a very different metabolism than a mouse. A 16-hour fast for a mouse is much longer than it is to us. So I don’t know if those benefits would extend.
Also, it’s not entirely clear that time-restricted feeding will produce the longevity benefit that we see in other sort of fasting, or fasting-mimicking types of diets. So for me, what it comes down to–it gives me much more liberty with what I eat during my feeding window. I don’t have to be nearly as restrictive when I’m feeding if I have that period off. Just in terms of my physiologic response.
Secondly, there’s a convenience thing. I hate being tethered to eat. I like knowing if I get into a pinch, I don’t have to eat right now. If I’m sitting in the airplane and they’re serving dog s**t, I don’t have to eat. I can wait another 5 hours until I eat. I also just feel much more steady in my energy levels. I kind of vaguely remember like 10 years when I was kind of eating a normal diet how I always had this lull in energy after lunch. There was the post-lunch pre-dinner “I just don’t feel good.” Not that I feel bad, but I’m not sharp, I’m not on my A-game. And I don’t even remember what that feels like anymore, which is not to say that I feel great all the time, but I definitely don’t have that vacillating energy level.
Joe Rogan: Yeah, I’ve said that to people when I eliminated most carbs from my diet. I have a friend of mine who talked to his trainer about that and his trainer was like “You’re crazy. Eat bread. Eat pasta. Don’t listen to him.” No, don’t listen to him. Just Google it. That stuff is f**king terrible for you. If you want to eat carbohydrates, get it from fruits. Get it from natural sources. If you have a trainer that is telling you to eat bread, get a new f**king trainer. It’s not what you need. There’s nothing wrong with eating if you want to occasionally, but when I eliminated most of that stuff from my diet, I felt the exact same thing. I felt that mid-day nap desire go away. Just the fogginess, at the end of the day you’re like “Oh God, I’m f**king tired.” And then I had to drink a cup of coffee to get ramped back up again, and it’s this never-ending cycle of having this insulin spike, and then this crash. And that is from carbohydrates. It’s from refined carbohydrates, having too much f**king sugar in your body. And everybody does it, look around.
Peter Attia: Alright, so this will be funny. So Google my name, and just put like “Peter Attia fat,” and you’re going to see a picture of me when I was a swimmer. Because all this time we were talking about me swimming, you’re assuming I’m a fit dude. I was a fit but fat dude. . . Fit but totally fat. [I was eating] non-stop carbs. . . I was definitely probably 30 pounds heavier. But body fat was much greater. . . I probably went through 3 or 4 bottles of Powerade a day because you’re training all day. Every post-workout was a carb re-feed, and so you’re in sort of this vicious glycogen-dependent state.
Joe Rogan: It’s crazy that there are so many folks out there living their life and they don’t understand that this is a process they’re going through. They just think this is eating and exercise, this is what happens. But it’s not. If you cut that off, push it away, enter into a completely different food source, just change the way you eat, your body will change. That concept that sounds like horses**it, what are you saying, what are you offering some miracle cure? I’m saying you will change the dimension of life that you operate in. It will change because you won’t be the same person. Who you are is dependent on a lot of things, but one of them is how much energy you have. How you feel. Whether you’re crashing. If you change the way you eat, you change the energy you have, you change the way you feel, it’ll change your behavior, it’ll change your choices, it’ll change your ambitions, it’ll change your potential. There’s so many things that will change.