"How FASTING Can Help You Lose Weight" | Dr. Jason Fung & Lewis Howes

Body really exists in sort of one of two states. You're either in the fed state or you're in the fasted state, okay? So when you're in the fed state, you're eating, insulin is going up. And as insulin goes up, its job, like its normal job, is to tell your body to store those calories, okay? So you can store it as glycogen, which is sugar, or it can store it as body fat, but that's the point. So you eat lunch or dinner, there's way more calories in that meal than you can use right at that point. So you want to store that. So when you don't eat, which is anytime you don't eat is called fasting. So when you fast, that means your insulin is going to drop and that's the signal for your body to now start pulling those calories out of storage, right? And that's the reason you don't die in your sleep every single night, is because we have the ability to hold some of those calories in storage. So in the fed state, insulin goes up, you're storing calories, or body fat. In the fasted state, you're not eating, your insulin's dropping, and you're using calories. So you're one or the other, you can't do both at the same time. So if now, you say, okay, I'm going to go- When I'm eating, I'm storing, I'm not using calories, is that right? You will shut down- Every time I eat, I'll store, I'm not burning body fat. You're not burning body fat, because you're putting in sugar, for example, and that sugar is going to signal that, hey, sugar's coming in, use the sugar that's coming in. Don't burn anything off my body. Yeah. Keep all that stored fat, keep it, just keep piling it on, right? Exactly. So the only way that you can actually use the body fat is to let the insulin fall and not eat. So if you are now eating constantly, so the minute you get up, somebody tells you, oh, you have to eat, you can't skip breakfast, blah, blah, blah, blah. And then you have to snack all day long. So now, if you look at studies, the average duration of how long people eat for is about 14 hours and 45 minutes. That's the average. So if you start eating at 8 a.m., you don't stop till 10.45 p.m. That's on average. That's the average. 14 hours, you mean a 14-hour span of eating from the start to finish, right? You may not be eating every moment, but you're eating every few hours within a 14-hour window. It takes about four hours for you to switch over into the fasted state. So the point is that before, where you'd eat breakfast, lunch, dinner, and by six o'clock, you're done, boom, now you shift into using those calories, and your mom would say, oh, you need time to digest, right? That's what she sort of said. But the point was that you need to start using those calories that you stored up during your mealtime. And that was the secret, that they could stay relatively slim. And now if you're eating constantly, then you never give your body a chance to switch over into that fasted state and start using those calories. The problem, of course, is that insulin stays high, which tends to keep your body storing calories. Your body, so the high insulin, for example, blocks fat burning. You can't burn your fat stores because your body's like, the instructions that I'm getting is to store energy, not use energy. I want to keep my stored energy for when there's a time that there's no food. The problem, of course, is that there's never a time there's no food, right? Every day is the same thing, right? 14 hours of eating and no time of not eating. And that's the point. So now if you understand the problem, you can say, well, how am I going to change this? Well, it's simple, increase the amount of time that you're not eating. And that's all intermittent fasting is. If you eat one meal a day, for example, or if you eat within a eight hour window or a four hour window or whatever, what you're doing is you're simply allowing your body to use the calories that have been stored, which is body fat predominantly. But that is precisely the reason you carry body fat. Like that body fat is not there for looks, it's there for you to use, right? And that's the whole point. What's so bad about using it? If you don't eat, you're going to burn it. Well, so again, go back to the 70s and everybody says, oh, you can't pass. You can't pass. Well, you know, they're eating breakfast, lunch, dinner. And if you're a naughty boy, you got sent to bed without dinner. So you went from 12 o'clock to eight a.m. 20 hours. You look good the next day. You're like a queen. You got a six pack. It's burning fat. Exactly. And nobody died. Nothing bad happens, right? There was nothing wrong with that. And hopefully you learned your lesson too, right? And that's the whole point is that there's nothing wrong. It's a natural part of our human physiology. If we couldn't survive without eating, like we would not be here today because when we were cavemen and cavewomen, there were periods of time. We didn't have food every day. Exactly. They couldn't. There might be a stretch of three, four or five days where there was no food and therefore they had to survive on their own body fat, which they did. And that was the whole point. So let's let our body, you know, use it because that's the most natural thing to do. What's the process for you, your day-to-day life? Do you eat one meal a day, two meals a day? Do you fast every month for a day? Are you always doing intermittent fasting? Is there a downside to intermittent fasting? What's your process? Yeah, I usually do a lot of sort of I rarely eat breakfast and I'll tell you that it didn't come. I mean, I started this in medical school and that was mostly because I really wanted to just roll out of bed and go like, you know, I'd wake up literally like five minutes before I left the door. You know, I brushed my teeth, put on some clothes and rolled out the door. I was, you know, it was just the way I was, right? And so I don't eat breakfast now because again, people say you have to eat breakfast, but there's actually nothing magical about breakfast. If you don't eat breakfast, what's going to happen? Well, my body, which is now burning fat because I've had eight hours of sleep, it's gone into sort of fat burning mode because that's the storage form of calories or it's burning sugar. It's just going to keep doing it, right? There's nothing wrong with it. So a lot of times I try and confine myself to sort of an eating window of sort of six to eight hours. And then once in a while, when I get very busy, I will do a 24 hour fast, which is a one meal a day. And then every so often I'll do a longer fast. And the longer fasts are actually not as bad as you might think, but they really disrupt your schedule sort of socially. It's a tough one because a lot of our socialization happens at meals. So I often have dinner with my family, for example, and doing those longer fast is really, really disruptive to that sort of thing, which is why when you look at traditional societies, like if you look at say, you know, during major religions, for example, there will be a period of fasting that's sort of universal. Everyone's doing it. So no one's feeling stressed when they smell the food. Exactly. So if it's like Good Friday or during Lent or during Ramadan for Muslims or, you know, during Yom Kippur for Jews or whatever, everybody's fasting. So it's actually terrifically easy because you're not disrupting the sort of social fabric of your life there. Whereas nowadays, if you fast and I've done this, it's just really hard to do. Physically, it's not hard, but it's hard. And I do it mostly, you know, when I when I've gained a bit of weight, usually after the holidays and after a vacation, I will sort of schedule a longer fast right after because I know that I can lose that weight very quickly. But that means I can enjoy myself. Like a couple of years ago, I went on a cruise and really ate too much. Just a lot. I had a lot and I knew it and I could feel it in my pants were tight and stuff. So I did sort of a three or four day fast. And I'll tell you, by the next week, I was back to my normal weight. Well, that's great because a week and but I got to enjoy the whole week prior where I really didn't look at what I was eating or how often I was eating or anything. I was like, this is my vacation. I'm doing this. And at the same time, I know, hey, I've got this next, you know, after this week, the week after, you know, very little to eat. And it gives you a great tool to use if you need it. Yeah, it's almost like either every day, don't indulge and balance and create a schedule where you're only eating in a certain window of time, whether before six, eight hours, which I'm hearing is kind of the which would be a great standard to have between four and eight hours of feeding time. Is that right? Yeah. Yeah. I mean, if you want to lose weight, you can do very well, of course, with a sort of standard 70s style, sort of eight a.m. to six p.m., which in a 14 hour fast every single night. Remember, they're doing eight for twelve to fourteen hours, say, every single night without even thinking about it. Like that's a secret because they don't even think about that. That's just a period of time that they're not eating. Right. But now, of course, the traditions are different. You can eat anywhere you want. You can eat in the theater. You can eat in a car like in the 70s. Stuff like that didn't exist. You didn't eat in a meeting in a boardroom, for example. Now you go to a meeting in a boardroom when there's food, there's donuts, donuts and cookies. Right. Somebody's ordered a plate of bagels or something like that. Right. It's like, well, why? We're having a meeting here. Right. So that's the that's the thing. So you can do very well with that kind of, you know, eight hour eating window for 10 hour eating window. You can do very well with it. But if you're not doing well, then you can extend it. And that's the beauty of it. You could extend it as much as you want. Right. So if you think about fasting, you could go three days, you go five days, you go 30 days. People do that all the time. But no food, no food. Yeah. So if you look if you think about fasting, so the but the amount of energy that you need to a pound of fat has thirty five hundred calories roughly if you need about eighteen hundred calories. So that's for like a regular person, not like an athlete or somebody who's working out a lot. It takes about half a pound of fat per day. So if you're dealing with a lot of obese people, like 100 pounds overweight, you could go 200 days. You know, if you want to lose 100 pounds, you could go 200 days without eating before you get and survive. Exactly. And be OK. Exactly. Be perfectly fine, because this is a very efficient fat is an efficient store of calories. Right. It's very efficient. That's why we developed this to keep you alive when there's no food around. Exactly. So use it. Does it affect your digestive system? Does it mess with your metabolism if you don't eat after a certain amount of time? Yeah. And what happens when you start eating again? Does that affect your again, your stomach, your intestines, your colon, your metabolism? What's affected there? And this is the interesting part is that everybody thinks that fasting is like the worst thing you can do when you actually look at the science of what happens during fasting. It's actually one of the best things you can do for yourself from both a mental standpoint and a physiologic standpoint, assuming, of course, you're not malnourished. Right. I mean, I'm assuming if you're the average American who's, you know, 10, 20, 30 pounds overweight, then this is something that actually has a lot of benefits. So there's a lot of sort of myths around it. One is that you're going to burn a lot of muscle. And the truth is that you don't. I mean, when you, you know, if your body, your body stores energy as body fat. So people say, oh, you're going to burn muscle. It's like, well, you've got to think that our body is so stupid that it stores energy as fat. But the minute you need it, it starts burning muscle. Right. Like, why would our body be so stupid? And if it were so stupid, how did we survive? Right. And it's like, you know, if you say firewood all went for the winter, and then as soon as it gets cold, you chop up your sofa and throw it into the fire. Like, why would you be so stupid? Right. Our body's just the same. It's not that. So, you know, and I know, and everybody knows that the way that you build muscle is that you exercise. Right. So if you have, you know, lift heavy weights, then your muscles become stronger. It doesn't become stronger because you eat. Right. That does nothing for building muscle. Like, otherwise, we'd be, you know, the strongest nation on earth. But we're not we're the fattest nation on earth. So that's the whole problem. Right. I mean, you're confusing two completely different things. There is a point during fasting where there is a little bit of protein breakdown. And that's where people get very confused and say, Well, you're burning muscle, but you're not protein is not the same as muscle. So our body has all kinds of protein, including all the connective tissue, like the skin and stuff that holds stuff in place. And some of that is often burned off. So for example, when you look at those shows where people get surgery, and they lose 150 pounds, they get all this flappy skin, that's not excess fat, that's excess protein. So that's, you know, it's functional tissue that you've never used up. So we actually see very little of that problem when people fast because there's a small period of time where they're actually using up the protein, your body will maintain its musculature based on what exercises stuff you're using. So another big myth, muscle burning is one thing. The other big, big myth is people talk about is starvation mode, or metabolic rate. So metabolic rate is the amount of energy that your body uses in a day, the number of calories you burn in a day. And this is what we see if you simply cut calories. So this is a standard medical advice, cut 500 calories a day, and you'll lose a pound of fat a week. What happens, of course, is that you cut 500 calories a day. And then your body quickly reduces the amount of calories it uses by about 500 calories. So now you're actually not losing any weight. That's what happens all the time. Because why does it stop? Why does it stop burning those calories? Well, it stops burning the calories by reducing its metabolic rate. So the metabolic rate is the energy that your body uses to say generate body heat, your liver, your kidney, your heart, and so on. We've known this for 100 years that if you simply restrict the number of calories, but keep the foods very similar, what happens is that your body is going to start using less. So because it doesn't like running a deficit, right? It's just like, if you normally make $100,000 a year, and you spend $100,000 a year, now you make 50,000. You don't keep spending 100, right? You're going to get thrown in jail. So you reduce your expenditure, same as a body. So it's getting less. So it's going to use less. And that's the natural reaction. It's important because it's a survival response. It cannot do anything different. So it's almost like you need to be extreme in order for it to burn and kill off these cells that might be harmful to you. But if you just do a little bit, I'm going to eat a little bit less today, it's not going to be that much. It doesn't work. And people assume that if you go to zero, which is fasting, say you fast for a full day, you have zero calories, you don't die, right? Because what happens is completely different. Now you've lowered your insulin, so you're changing the hormonal profile of the body. And as you do that, you're now switching fuel sources. So instead of using food as your fuel, you're switching it into body fat, just like those hybrid cars where you go from gas to electric, right? So it's using food. And then boom, it goes, okay, I have no food coming in. I need to switch over now into body fat. And then it goes, whoa, I have like 500,000 calories of body fat here. So why do I need to cut it down? And the point is that it doesn't because assuming if you have no body fat, of course, it's a problem. But for people who have adequate source of body fat, which is most of us, and truthfully, most people do it for weight loss, too much body fat, then what happens is that there's so much there. Why wouldn't you use it? Because it's a fuel source. That's all it is. That's the way you have to look at the body fat. If you're eating all the time, you can never use your body fat. Because your insulin's here, your insulin's high, you're using food. Then you get hungry, so you eat some more, right? You have a snack, you have a low fat muffin. You stay here. You can only burn food. All that stuff over there, those 500,000 calories of body fat are completely inaccessible for your body. So if you simply dial it down like this and say, okay, instead of 2000 calories, I'm going to eat 1500. I'm going to eat 10 times a day, keeping myself here. Now you only have 1500 coming in. You can only burn 1500. You can't access that. If you go to zero, you go, boom, and then your body burns the full 2000. So they did a study, for example, where they took people and fasted them for four days and measured how many calories they're using. They also measured their VO2, which as you know, is something that it's a measure of how much cellular work your body is doing. And what they found, so they measured the metabolic rate at time zero. Then they measured it at four days of zero food and they were burning 10% more calories than they were per day than they were when they were eating. The VO2 was 10% higher. You're doing more work. Your body is actually not shutting down. It's revving itself up. And again, there's a good physiologic reason for that. And we know that when insulin goes down, when you switch yourself into this sort of mode that you're burning fat, other hormones go up, including your sympathetic nervous system, which is your noradrenaline. So you're actually pumping your body up. The reason for that is sort of, again, it's a survival response. So imagine again, we're caveman and it's winter and there's no food. So if you don't eat for two days and you get weaker, you're never going to eat again. You're going to die because every day is going to be harder. You're going to circle the drink. So our body's just not that stupid, right? So what they do is that your body says, okay, there's no food coming in. Boom. I'm going to switch you over to body fat and then I'm going to pump you up so that you have energy. You go out there, you go kill that woolly mammoth. You're focused, you're clear, you're in the zone, everything. Exactly. And that's the reason that we actually pump ourselves up. And the mental aspects is actually fascinating because people also say, well, I have to eat because I have to concentrate. It's like your concentration is actually much higher when you don't eat. Think about when you had a huge Thanksgiving meal. Well, were you really sharp or did you really want to just lie down on the sofa and watch some football? You don't have any sort of focus. But if you think about animals, it's the same thing. Lions, they just eat, they're just lounging around. But if you're the hungry wolf, that is a very dangerous animal because he's focused, he's ready to kill you. Same thing for us. Our level of concentration, our mental ability, mental agility goes up significantly when we're hungry. If you think, oh, you're hungry for this, hungry for that, that doesn't mean you're falling down lethargic. It means you're focused. So it's interesting because there is this book a few years ago called Unbroken, which is a biography of this fellow who went to a prisoner of war camp in World War II Japan. And he was talking about starvation and they were literally starving. They eat almost nothing for the full day. And he's talking about how his other prisoners were doing these incredible mental feats. So one guy was reading a book entirely from memory. Another guy learned all of Norwegian in a week. And so the guy says, this is simply the mental clarity of starvation. So it was widespread. Everybody was starving and they'd see these incredible feats that nobody else in the world could do all the time because your mental ability is ramped up to such a high degree. And then in the ancient Greece, the ancient mathematician Pythagoras, he would require his students to fast in order to come to his class because otherwise he thought they had no mental agility. If you're looking for more greatness in your life, make sure to check out this video right here. And also check out our free PDF, The Three Secrets to Unlock the Power of Your Mind to Help You Change Your Life. Download it right here. Humans who eat two cups of mushrooms per week do not get Alzheimer's disease.