Live Long and Master Aging podcast



Transforming human health through fasting

William Hsu: L-Nutra


The popularity of fasting has surged in recent years, although there are myriad approaches to restricting food intake to promote good health.  One system, known as ProLon, involves mimicking the effects of fasting, by allowing small meals to be consumed during the diet.  I have followed the progress of this fasting mimicking diet (FMD) ever since I took part in a clinical trial in 2013, to explore the regime’s feasibility and safety. In this interview Dr. William Hsu, Chief Medical Officer with L-Nutra, the company that markets diet, explains the latest science behind periodic fasting nutrition and the differences between the various protocols that are often labeled as ‘intermittent fasting.’

The Live Long and Master Aging podcast, a HealthSpan Media LLC production, shares ideas but does not offer medical advice.  If you have health concerns of any kind, or you are considering adopting a new diet or exercise regime, you should consult your doctor.

Connect with Dr Hsu and L-Nutra: Bio | Website | Instagram | Facebook | Twitter | TikTok

Read a transcript 

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Related LLAMA interviews

Additional reading

  1. Early results of the 2013 fasting mimicking diet trial that Peter Bowes took part in as a volunteer.
  2. The experimental diet that mimics a rare genetic mutation – Peter Bowes has been on a new diet that claims to guard against disease and slow aging. Then he met a group with a mutation that lets them eat what they want while enjoying the same protection.
  3. The Longevity Diet by Prof. Valter Longo

“Just giving yourself a little break, emotionally and biologically to the food that you’re addicted to. It could do wonders for you.”

William Hsu

Topics covered in this interview include

  • A doctor’s experience with patients struggling with lifelong conditions such as obesity, diabetes and other conditions
  • Discovering the mechanisms behind fasting
  • Explaining the fasting mimicking diet (FMD) and why it allows small meals
  • The differences between fasting-based diets and time restricted eating
  • The ultimate goal: living healthy for a longer period of time.
  • Better understand the frequency with which a FMD can be used for optimum health
  • Distinguishing between fasting and starving
  • Why fasting does not replace healthy living liffestyles
  • Understanding IGF-1 as a health biomarker 
  • The link between fasting and resolving issues such as brain fog
  • Developing a ‘new relationship’ with food
  • Living with longevity in mind is offering listeners to LLAMA a 10% discount on its range of products – NAD boosters, Sirtuin activators, senolytics and more.Use the code LLAMA at checkout. Any health queries can be answered by emailing the team at

Affiliation disclosure: This podcast receives a small commission when you use the code LLAMA for purchases at – it helps to cover production costs and ensures that our interviews remain free for all to listen. 

This interview with William Hsu was recorded on February 9, 2022 and transcribed using Sonix AI. Please check against audio recording for absolute accuracy.  

William Hsu: [00:00:00] A lot of people ask after the five days, What can I eat now? You know, I feel so much better. Why did I do what I used to do? What can I do to improve my health? Just giving yourself a little break, emotionally, biologically to the food that you’re addicted to. It could do wonders for you.

Peter Bowes: [00:00:21] Hello again and welcome to LLAMA the Live Long and Master Aging podcast. I’m Peter Bowes. This is where we explore the science and stories behind human longevity. Now, nine years ago, how time flies, 2013, I took part in a clinical trial at USC, the University of Southern California, which explored the feasibility and safety of a fasting mimicking diet in humans. It followed studies in rodents that showed that a very low calorie, low protein fasting mimicking diet, the FMD improved metabolism and cognitive function, decreased bone loss and the incidence of cancer and extended longevity in mice. In humans, the trial I was part of,three monthly cycles of a five day FMD reduced multiple risk factors of aging, the scientists concluded. Well, fast forward to the present day and the fasting mimicking diet is being used as a tool to extend human healthspan around the world. Today we’re going to talk about the science and where it stands today. We’ve done several interviews with Dr. Valter Longo, whose original work inspired this research and also the diet that it led to.  We’ve also spoken to Dr. Joseph Antoun, the CEO of L-Nutra, the company which markets the ProLon Diet, as it’s known. Those interviews are available at our website, well – worth a listen to understand some of the background to what we’re about to discuss with Dr. William Hsu. Dr. Hsu has been the Chief Medical Officer with L-Nutra since 2019. He is an endocrinologist and joins us now from Los Angeles. Dr. Hsu, welcome to the Live Long and Master Aging podcast.

William Hsu: [00:02:06] Peter, thank you so much for having me on your show.

Peter Bowes: [00:02:09] It’s a real pleasure to talk to you. What brought you to this company and especially what brought you as an endocrinologist to this company?

William Hsu: [00:02:16] Yes. So as an endocrinologist, I took care of patients struggling with lifelong conditions such as obesity and diabetes and other conditions. And one of the biggest challenges I’ve always had in the clinical practice was the fact that most of my patients knew what to do in terms of improving your health. They knew what they ought to be doing, right. That is eat better less and exercise more and lose weight. Right. And these things, I think we’ve heard enough, but the challenge had always been, how do I do it? How do I do it consistently over time? And so the separation between what we know and our inability to actually do it has always plagued my practice for as long as I’ve practiced, which was about 20 years. And so when this whole story of fasting broke in the scientific world, I was thinking, how come the conventional medical world have never asked and never really look into the mechanism of fasting? And because fasting is such ingrained in every living organism, right from the simple single cell organism to complex organisms such as, as humans, this is one of the most under tapped interventions. And so I began to look at the signs and began to talk to my friends, other scholars in the area of longevity and health and looked at some of the research in the field. And it intrigued me. The evidence that the science and the potential to transform human health, I think, was what draw kind of draw me to the company.

Peter Bowes: [00:03:57] And you referred there to the fact that people think about regular diet or traditional diets, maybe even yo yo diets when they are tackling a weight problem, they think about exercise and those maybe even old fashioned interventions. I always try to stress from my understanding that they are still good things to do to eat, let’s say a sensible, balanced diet and plenty of exercise. They can’t be underestimated, can they?

William Hsu: [00:04:26] You’re absolutely right that I think while we know what is absolutely the best for us and that is, you know, living a lifestyle that’s consistent with regular activities and good diets and good intake and more plant based diet. I think the missing piece is our inability to do it now. We like to have to do that every single day, of course. Should we continue to strive towards that goal? Absolutely. But the reality is far from perfect. And so is there other interventions that can be easily done and can give you many of the of the benefits that we’re looking for is sort of the next chapter in science.

Peter Bowes: [00:05:05] Well, as you can probably gather, I’ve got quite a long term interest in this this particular this very specific diet. Having been involved in that clinical trial, which I can tell you, I can remember it vividly, it was quite an experience and it was new for all of us, the scientists involved in it at that stage. And and it’s led to something which is really quite big in terms of the expansion of this diet. I think it might be useful just to go back to basics and explain what the Fasting Mimicking Diet FMD is and how it works.

William Hsu: [00:05:36] Yeah, so so the Fasting Mimicking Diet is, is you could tell from the name it’s about a set of meal plans. It’s a five day meal plan that mimics many of the benefits of fasting. And so it’s able to do that because, you know, we think about fasting is really has been designed by nature all throughout biological lifeforms because if you look at the environment around where we live, most of the days we struggle as well as any living form with paucity of these nutrients around us, where there is a lack of nutrients. Animals have to go out to hunt in order to be fed. Right. The tigers have to … hunt even single organism. It doesn’t live environmental plenty. So that means that over time, the each organism has developed a way to cope with times when there is no food around. And the body uses those opportunities actually to recycle some of the older and more broken down stuff, a more worn out components of the cells and replace with new ones. And so the body is actually able to leverage those times as fasting and turn that into a survival mechanism. But the challenge is always that we want to get the maximum level of fasting into the body so that we can get most of the effect of it out of fasting, but not too long so that most of us can actually do and endure through periods of fasting. That’s always been the struggle there. Right. We know that if you fast a little longer, you’re going to get a little bit better benefits. But there is a limit to to how long you can fast and it’s difficult to fast. And therefore, Professor Longo has come up with this intervention called the fasting mimicking diet. It took the understanding of the intersection between nutrients and nutrition, health and longevity, and figure out a way to mimic fasting by providing essential nutrients during fasting so the body can actually see some food be supported through the fasting period. At the same time, the cells inside of the body actually would experience fasting as if it were water fast.

Peter Bowes: [00:07:49] You’ve just used a number of terms that we hear about a tremendous amount these days. Longevity, fasting, intermittent fasting is a phrase. It’s an umbrella phrase really, isn’t it? It doesn’t refer to one specific diet. And I wonder sometimes if it is still confusing for people when you’re talking about a fasting mimicking diet. Others talk about an intermittent diet that involves maybe fasting on two days of the week. Others will do a 6.9 time restrictive eating regime. It gets mighty confusing, doesn’t it, Peter?

William Hsu: [00:08:21] You’re absolutely right. So let me try to help here. I think fasting is obviously a continuum, right? So fasting one day within a day. But a lot of people do what’s called time restricted eating. Right. That’s you’re limiting the number of hours you’re eating within a certain period of time. For example, if we say 16:8, a lot of times that means 16 hours within the day you will fast and then you would limit the number of hours of consuming your food within 8-hour window. So that’s 16-8. Some people do, you know, 14:10 so that could be 14 hours of fasting, 10 hours of eating food. So that is the term that that’s been used to describe that kind of pattern that’s called time restricted eating. That’s the most common type of intermittent fasting. So intermittent fasting, again, we give definition to it, I mean, by nature is always a continuum, right? So intermittent fasting, most people really refer to fasting no longer than two days in a row. So generally it’s a day or less than a day. Generally, those two days are not consecutive days. So you could be two days out of the week where you are not eating or eating very little. And the rest of the week, the rest of the five days you eat, consume a normal diet. That’s like a 5:2 diet. They all fall under the umbrella of intermittent fasting. There is a distinct artificial category, we call that long, fast, right? Some people call it periodic fasting, some people call it prolonged fasting. I mean, what they all means, it’s more than two days of consecutive fasting. If you think about most of the fasting patterns around the world in history, in different cultures, in different religions, those are the long fasts, right? So people will fast for a couple of days for spiritual reasons, for health reasons. They generally involve these longer term fasting, not so much intermittent fasting. So they’re and from a scientific angle, we separate the intermittent fasting from the long fasting because they actually have distinct biologic impacts.

Peter Bowes: [00:10:29] And the use of the word longevity. Is that the ultimate goal? Whatever the precise regime that people are using, the goal is healthspan, isn’t it? Which is you could say that is our own personal longevity, how long we’re going to live and be healthy and active and involved in the world and physically able to do what we want to do.

William Hsu: [00:10:49] That’s absolutely right. I think modern medicine has prolonged the number of years we live. But as you and I could tell, as we see the scenes in the hospitals, they’re full of elderly individuals who are struggling with multiple conditions. And just give you an example, somebody living with diabetes on average would take eight medications. So modern medicine is prolonging life. But I believe there’s something more we can do to support living healthy for a longer period of time.

Peter Bowes: [00:11:22] And so when the scientists on the original studies concluded that the FMD reduces multiple risk factors of aging, that’s really what you’re talking about. Those risk factors are the risk of developing diabetes, heart conditions, cancers, other conditions related to old age?

William Hsu: [00:11:41] Yeah, I think that’s the aspiration of for all of our research is how can we incorporate fasting on a regular basis and in the most optimal way so we can give people the chance to live long and healthy? And certainly that’s an aspiration that we all have here at the company.

Peter Bowes: [00:12:02] And you mentioned periodic fasting. And my understanding of periodic fasting as it applies to the fasting mimicking diet is that it is something you’re not necessarily doing all the time. In fact, explicitly you’re not doing it all the time. You’re doing it in five day spells every perhaps three months, six months, nine months, depending on you as an individual. What I’m curious to understand is over the years that this diet has been developed, have you developed a better understanding of the necessary frequency of this diet for different people?

William Hsu: [00:12:34] Right. And that’s a really insightful question. If you think about how fasting really improves health, it’s really by causing a level of stress to the body. A lot of people think all fasting is just low calories. You’re eating less food. It’s actually very different, right? If you take the low calories, you have to do it for months to see results because it’s the accumulation of a calorie deficit that results in weight loss. Right. And that produces many of the effects. The mechanism as to how the fasting impacts health is actually through a stress. And a lot of people say, well, Will, why would you want to have stress in the body? Actually, stress is could be very good. For example, what’s exercise? Exercise is the stress onto your cardiovascular system. It’s a stress until muscle. Without those stress, for example, astronauts in space, they don’t have the stress of gravity. Guess what? They’re muscle fail to grow. The muscle actually will become weaker in atrophy. So stress is actually a natural and necessary part of making us healthy. So let’s take you through sort of the scientific world here. When a cell – let’s take a cell, right? When you deprive it of nutrients, what does the cell do? The cell says, hey, you know, all my sensors are telling me there’s no glucose, there’s no protein, there’s no food coming in. I cannot grow. What does that mean? That means I need to find an energy source. Where do I find it? Let me look inside. Are there things that are a little older? There are things that are a little bit more worn out. You know what? I’m going to take them and recycle them to produce to produce new ones, because I am not getting any nutrients from the outside. That survival mechanism right. In response to the stress of no food, it’s actually turns out to be so healthy to the cellular renewal that the inventor or the discoverer of this of this pathway, this autophagy, what I just mentioned, describing that process, one won the Nobel Prize in 2016. And so the question here is, how do we leverage that mechanism to allow the stress of no calories coming to the body and use it to our advantage? Now, you certainly don’t want to do it all the time. If no food is good for health, then starvation should have been very good for all, for all the humanities. But in fact it’s terrible is detrimental to our health. So there is a limit and finding that limit to make sure that you don’t overdo the fasting. But doing it in such a way where it optimizes the stress to the cells can be critical to our health and wellness.

Peter Bowes: [00:15:10] That’s a very interesting point you make that, you know, we tragically live in a world where millions of people are starving and it’s a horrendous situation. Look at what’s happening in Afghanistan at the moment with people just simply unable to get food. And yet here you and I in the Western world, in the developed world, talking about an element of, it’s not starvation, I think that’s the wrong word to use.

William Hsu: [00:15:31] That’s the wrong word, yes

Peter Bowes: [00:15:32] …element of fasting. But it is – it involves not eating as much and it involves perhaps not eating as much to an extreme for some people over a very limited period of time. And it’s clearly important to make the clear distinction between what is enforced on some people simply because they don’t have the means and the wherewithal to get food and what we can do to just pull back for the benefit of our own health.

William Hsu: [00:15:55] Yeah. And so let’s, you know, let me use an analogy to help us, our listeners, to understand this approach. Let’s recall the days of our our, when we were students. You know, we were supposed to study for every day. That’s what the teacher always tells us. You’ve got to do homework. You’ve got to study every day. Peter I’m not sure about you, but I’ve never studied every day. I cram before the exam, right?

Peter Bowes: [00:16:24] Yeah, I think we all did that.

William Hsu: [00:16:25] Yeah, we all did that. And did we survive? We survived, right? Did we learn something? We learn something would have been better if we were to study every single day. Yes, for sure. But that cramming that stress of exam coming up forces us to digest a large amount of information. And we did okay. We pass through the these tests. Fasting is almost like that. Right. So, you know, would have been better if we eat a healthy diet every single day. I’ll give you $10m. Right. If you could do that every single day. That is the way we’re supposed to do. But are there additional things, you know, those cramming the stress caused by the lack of energy? You know, it forces us to really to change our biology from time to time. The stress cannot be every day. Otherwise we will be overstressed. Right. And but when it comes on on a periodic basis, hence the idea of periodic fasting can really introduce another way to boost up our health and wellness. Again, please don’t take me wrong. I’ve never say that fasting can replace a healthy living style lifestyle. No. When when it’s incorporated, it can add to the the lifestyle that we we certainly want and can benefit from.

Peter Bowes: [00:17:37] This is the Live Long and Master Aging podcast. Our guest for this episode is Dr. William Hsu, Chief Medical Officer with L-Nutra. Let’s dig just a little deeper into the science. I know one of the effects of this regime and other fasting regimes is lowering of IGF-1 levels, the growth factor, insulin-like growth factor one. And this has been shown in numerous studies. Why is that beneficial for us?

William Hsu: [00:18:05] Yeah. So so IGF-1 is a global biomarkers it simply – it’s a signal that there isn’t too much nutrients floating in the body. There’s isn’t enough pressure to push the cells to grow all the time. In a note, there was a recent study that showed that the correlation of that IGF-1 level to mortality, which is the length of our life, is actually a U-shaped relationship. Surprise, surprise. Right. It’s actually everything is like that, right? When your body weight, you know, when when you’re too lean, it’s not good for your longevity. When you’re too heavy, it’s bad for your longevity. Same thing with this IGF-1 level. So what this is basically is telling us is that, for example, for adults like you and me, do we need a signal for growth all the time? Do we want the body to be pushed to growing all the time in the growth mode? Probably not. If they think about a car, a performance car, a sports car, you’re pushing your pedal to the metal all the time. You know what’s going to suffer. Your wheels are going to get worn out very quickly. The body works like that. Yes, it certainly needs to be sustained. It needs to grow, but not growth all the time. We need time, a break. We need time of rejuvenation. And that IGF one is that marker, that signal to tell the body, you know, if it’s in a good level, that means there are times of growth, there’s times of resting … In our society where we have so much nutrients, we are pushing the body to grow all the time. We’re giving all the cells all the signal to grow, grow, grow all the time. I think the fear is that too much of that signal is actually not good for our health from time to time. That break from nutrition, from over nutrition, it’s amazing what a little break can do to our health.

Peter Bowes: [00:19:57] And of course, growth hormone is crucially important to us as we are growing, as we are babies, as we are young children, those vitally important first few years, and the syndrome known as Laron Syndrome, that affects just a few hundred people around the world that results in stunted growth because there’s a lack of IGF-1.  And this is due to a genetic defect. I know this is something that Valter Longo has studied very closely, especially the the community of people with Laron Syndrome in Ecuador. That is, and I say, a very small community of people, but it does beautifully illustrate what you’re talking about and the role of IGF-1.

William Hsu: [00:20:34] Yeah, and it’s important that much like exercise, right? We say exercise is great for our body, but can you imagine you’ll have the exercise for 24 hours straight with no break. It’s really the combination of exercise and then rest. Same thing is the combination, the proper combination of fasting and a way, right? Sort of the fast the feeding and the fasting, right. So the proper nutrition, right. following a periodic fast a fasting period that turns out to be really the I believe to be a magic formula that we’ve not tapped into in conventional medicine.

Peter Bowes: [00:21:16] Of course, the thing I didn’t mention there about IGF-1 and Laron syndrome is the fascinating scenario that as people get older with Laron’s syndrome, the incidences of those killer diseases of old age almost don’t exist, which is remarkable in terms of the science. And there’s the link between what we are trying to do, what you’re trying to do with the diet by reducing IGF one levels to some extent, and what has been shown in real life away from the diet in very remote communities in Ecuador, what is happening to these individuals?

William Hsu: [00:21:50] That’s exactly right. And I think we have now studied in multiple instances where we’ve shown multiple cycles of fasting, mimicking diet done monthly for three or four cycles, has many of the same benefits as being on an everyday, good diet. Again, you know, I’m a 100% proponent of having great diet every single day, but just the mere introduction of stress brought on by fasting, followed by good eating that really can push the body into that that growth and break and rest, you know, that combination. It’s what I call the union of the body. And I think I think medical science has just begun to look at this and you will see probably a lot more research done now. A lot of news right now. More on intermittent fasting and more on fasting. I think it’s going to be very exciting in the next couple of years to see all the research in this area and we’ll learn a lot more.

Peter Bowes: [00:22:54] I think it is interesting broadening things out a little bit, coming out hopefully coming out of this pandemic that people are realizing perhaps like never before, the importance of everyday health and the importance of of not having those underlying conditions that we know through through many, many tragic examples. Oftentimes, those are the people who suffer worse from a virus, and maybe there’ll be another virus in the future that will have similar effects.

William Hsu: [00:23:18] Absolutely. And unfortunately, I think there was a recent report that 50% of all Americans, or maybe even around the world have gained weight and meaningful amount of weight gain over the pandemic period. So it’s really a wake up moment for all of us.

Peter Bowes: [00:23:34] Let me ask you about the diet itself, and this really fascinates me. Having used the diet myself periodically over the last few years, following the initial clinical trial and the clinical trial itself was quite intense. It was the fasting mimicking diet every month for three months, which is not something that I’ve repeated. It’s been over a period of several months, but I’m interested in terms of the feedback that you might have had from people around the world in terms of their ability to stick with it. Because one of the things I found difficult was the sticking with it in terms of the mundane nature, relatively mundane nature of the food there. Yeah, fairly tasty foods, they’re plant based soups and little bars, but my interest was slightly less each time in terms of diving into the diet. How have things evolved in that respect to make the diet in terms of being flavorsome food and attractive food perhaps more interesting to people?

William Hsu: [00:24:27] Yeah, I think, you know, the good news is that you don’t have to in real life, right? You do not need to be on a monthly cycle forever and ever. I think that’s never been the intention. Right. I think in the clinical trial, what we wanted to show is, is that initial in that initiation period, after three or four months of monthly cycles, a lot of people actually are able to go on to a every three, four months cycle. And I often think about that as almost like a a deep clean, almost like a spring clean of the body. Right. So so every weekend we could be cleaning the house, but we would never take down the curtain. We will probably not shampoo the floor or the carpet, but every so often, right. Every season is probably a good idea to do that. And the fast mimicking diet in this case would be the ProLon five day fast can be very safely done every three or four months. And that would take the sort of the mundaneness as in the routineness out of our everyday living. I think in the clinical trials, certainly we want to have that initiation start, right, especially if you have a specific metabolic goal. That monthly cycle does drive the speed towards that goal. But once you’re on a maintenance phase, it takes about three or four months every cycle to continue to maintain the IGF-1level and other cellular effects.

Peter Bowes: [00:26:00] And I guess the incentive for the vast majority of people is results. And if people are seeing results from the earlier cycles, perhaps that’s incentive enough to do the next five days?

William Hsu: [00:26:11] I think there you know, the results really come in a couple of forms. You know, one is certainly the IGF-1. You don’t experience it. That’s a laboratory test. That’s an objective test. But people what experience they experience immediately is they see that much of the weight loss is actually in the trunk area. So that’s always encouraging, right? Knowing our population, this is a fat driven weight loss. And so we have now numerous studies to show that when you go through a prolonged fast, you’re actually burning those fat in the mid trunk and you’re not using your muscle to be juiced up as a fuel. This is actually very important. A lot of people on a low calorie diet, they actually will lose both muscle mass as well as fat mass. But because fasting is a stress, it’s a stress onto the body. So you have increasing growth hormones that actually help to preserve your lean body mass during the five day cycle. And also because it’s just five days is not five months of a low calorie diet. Right. The mechanism is really about the stress. You actually preserve your muscle mass and muscle function as opposed to simply be on a low calorie diet. And so there are these experiences people see, they look at their waist size. It gets smaller, they feel strength after they fast. And then not to mention, there’s a lots of mental health effect. Right. So people who’ve gone through these fasts, I mean, this is why people used to fast for religious reasons or for cultural reasons is because it helped them focus. They have the mental health energy, they have the mental energy. There’s sort of brain fog. They experience a resolution of that brain fog. They feel the sense of energy. And that’s what people like feeling. They like feeling light. They like feeling better. And fasting does bring you many of these benefits.

Peter Bowes: [00:28:06] And that’s one of the benefits. That’s one of the implications of this diet that perhaps takes you by surprise after what about day three, when you begin to feel that sort of mental energy. And that’s when you’re you’re using ketone bodies for energy as opposed to glucose because you’ve you’ve used up all your glucose and your body is working in a different way. And I always remember the first time that that happened to me, and it’s like a light bulb going off to some extent. You’re you’re in this fasted state, but all of a sudden you’re not craving food and you’re full of energy.

William Hsu: [00:28:41] And a lot of people do report. I think now now the Prolon we probably have over a million units around the globe now. And one of the consistent feedback that we get is people feel that five day prolonged fast changes their relationship to food. And that’s actually very important because, you know, we’re so used to to getting the certain highs from certain food. We’re addicted to certain flavors, certain composition that five day fast cuts away that connection. It could be a biological connection. It could be a emotional connection. But a lot of times after five days, a lot of people ask after the five days, what can I eat now? I want to eat better now you know, I feel so much better. Why did I do what I used to do? What can I do to improve my health? And that’s really a testament to just giving yourself a little bit of a break emotionally, biologically, to the food that you’re addicted to. It could do wonders for you.

Peter Bowes: [00:29:43] I always remember it had exactly the same effect on me and the five day. It’s quite a simple way of living. It’s all prepared for you that there isn’t much thinking involved because it’s all set out there days 1 to 5 and as I say, mostly sort of plant based soups and tiny little bars. What I became increasingly aware of, and this has happened several times over the five days, is the food advertising that’s all around us. And that’s impossible to escape because you continue your normal life by en large, maybe reduce your exercise a little bit during those five days. But you’re still watching television. You’re still seeing burger and pizza ads on TV. And that, for me, was that kind of almost visceral response to just seeing food and seeing food that I know is bad for me, that is not healthy and not wanting to eat those foods in the future.

William Hsu: [00:30:34] And coming back to my role as a clinician, I wish many of my patients could get to a stage in their lives or in their health journey to be experiencing that, to say, wow, you know what, look, I want to I want to eat differently. That motivation. I mean, I as clinicians, we cannot give patients that motivation. That motivation has come from within. And it’s nothing like you walking through the five days of fast and you experience that mental change, that energy change. You experience the lightness, the sense of lightness as you go through a five day fast and reaching the conclusion yourself that, hey, I want to have a different relationship with my food. I think it’s every doctor’s dream and I think many of our listeners being the people who were struggling to get to a new level of health, and this could be a very interesting tool to consider.

Peter Bowes: [00:31:32] Let me ask you, Will, just in concluding from everything that you’ve learned about this particular science and obviously your experience as a doctor, how do you live your life every day with your longevity in mind? What do you think about most?

William Hsu: [00:31:45] So I thank you for asking that question. I think since I have joined the company, I certainly have changed the different, you know, my eating pattern. I think there is a place for both intermittent fasts as well as these prolonged fasts. You know, I mean, I cannot use a spring cleaning to give me excuses for not tidy up my room on a on a week, you know, a weekly basis. And so I do use Prolon once every three months that just for my to maintain a healthy longevity, my own personal goal. But at the same time, while I’m not doing these long fasts, I do practice time restricted eating and generally about I live with my consumption to about 8 to 10 hours a day and for the rest of the 12 to 16 hours at times. I generally do not eat, so I give my body a break on a daily basis. So it’s a combination of both.

Peter Bowes: [00:32:43] And it’s getting into a routine to do that, isn’t it? It’s something that I do as well. Try to stop eating by 6` or 7 p.m., not start again, maybe 8:00 or the next morning. It’s a routine to get into, but once you’re in the routine and you don’t think about it, all of a sudden it’s part of your lifestyle and it becomes quite easy, perhaps easier than you ever thought it could be. Contemplating this maybe a few years ago, having never heard of time restricted eating, it actually becomes easy quite quickly if you do it regularly.

William Hsu: [00:33:12] And a lot of us feel fasting’s so far away from me because wow, that’s that’s like for those biohackers and no, no, I would say everybody fasts, believe it or not, when we sleep, we fast. It’s just a matter of hours, right? All of us, our body all go through fasting period. So my advice is start today, start with a time restricted eating, you know, after certain hours at night, don’t put food in your mouth. I think that’s a relatively easy to do. Realizing that we don’t eat always out of hunger. We as human beings, we out of habits, out of emotions, out of our social connections. And to factor those things into your decision making and just to say, you know, after this hour, there’s no food, can go a long way to supporting your healthy longevity lifestyle.

Peter Bowes: [00:34:05] Well, I think it’s really fascinating research, obviously continuing and evolving research. I wish you all the best with it. Thank you very much indeed.

William Hsu: [00:34:13] Thank you, Peter.

Peter Bowes: [00:34:14] And if you’d like to read more about Dr. Hsu’s work, the fasting mimicking diet in particular, I’ll put some details into the show notes for this episode. You’ll also find a transcript of this conversation at the Live Long and Master Aging website at That’s double  And as I mentioned earlier, my interviews with doctors Valter Longo and Joseph Antoun are also available at our website. Well worth a listen if you’d like some more background to this subject in social media, you’ll find us @LLAMApodcast. You can contact me @PeterBowes or email me It’s always good to hear from you. This is a Health Span Media production. You’ve already found us. If you feel like exploring a different platform, we’re available at all of the major podcasting sites, including Apple Podcasts, Spotify, Stitcher, Pandora and Audible to name a few. Wherever you listen to us, do take care and thanks so much for listening.

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