The Dr. Jules Plant-Based Podcast
Hey, I’m Dr. Jules! I’m a medical doctor, teacher, nutritionist, naturopath, plant-based dad and 3X world championships qualified athlete. On this podcast we’ll discuss the latest in evidence-based and plant-based nutrition, including common nutrition myths, FAQs and tips on how to transition towards a healthier dietary pattern and lifestyle that creates little friction with your busy life!
The Dr. Jules Plant-Based Podcast
The Truth About Fasting: Beyond the Hype
Fasting has become a health buzzword, but beneath the hype lies a complex metabolic tool with specific benefits and important caveats. In this comprehensive exploration, I break down the science behind different fasting approaches and reveal why not all fasting styles deliver the same results.
The episode distinguishes between four major fasting types that are often confused: prolonged fasting (multi-day), intermittent fasting (alternate day or 5:2), time-restricted eating (daily eating windows), and fasting-mimicking diets (low-calorie regimens). Each approach affects your body differently, and understanding these distinctions is crucial before embarking on any fasting regimen.
While fasting shows impressive benefits for weight management, metabolic health, inflammation reduction, and potentially even cancer treatment support, these advantages come with important qualifications. The podcast reveals a critical insight often overlooked: fasting paired with poor nutrition during eating windows can negate most benefits and potentially cause harm. For those primarily interested in weight loss, the evidence suggests early time-restricted eating (finishing dinner by 5-6pm) provides the most sustainable approach with the strongest scientific backing.
The episode also addresses special considerations for athletes, medication users, and those with specific health conditions. We explore why some people might experience rising cholesterol with certain fasting approaches, how fasting affects muscle maintenance, and the emerging research on fasting's role in cancer therapy.
Whether you're curious about skipping breakfast, considering a five-day fast, or simply want to understand how your eating pattern affects your health, this evidence-based breakdown cuts through the confusion to help you make informed decisions about incorporating fasting into your lifestyle. Subscribe now for more science-backed insights on optimizing your health through evidence-based nutrition and lifestyle medicine.
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Dr. Jules
Hey everyone, welcome to Season 2 of the Dr Jules Plant-Based Podcast, where we discuss everything from plant-based nutrition to the main pillars of lifestyle medicine medicine. Yo, plant-based buddies, welcome back to another episode of the podcast. Today we're going to be talking about the science of fasting. Part one will be the what, the why and the how to fast, and part two will be about longevity, cancer, inflammation and possible risks that could come with fasting. Now, fasting is very popular. Some people think it's the fountain of youth, and a lot of hyperbolic claims surround fasting. But the most important thing is that there's a lot of nuance to consider. There are potential risks with fasting, so if you're going to do it, you want to make sure to do it the right way. So in this two-part series, we'll unpack everything you need to know about fasting Not the trends, but the science behind it, Whether you're curious about skipping breakfast or considering a five-day fast this is for you.
Speaker 1:Now let's start with a simple truth Fasting is not biologically extreme. Now it may be socially extreme, but we've evolved to go through cycles of feast and famine. In fact, our metabolism is built to be able to switch between storing energy and burning it. This ability is called metabolic flexibility. What I would consider to be extreme is eating every two hours. That's a more modern invention.
Speaker 1:Now fasting is an umbrella term and there are several different evidence-based types of fasting. So let's talk about the major ones First. We have to differentiate prolonged fasting from intermittent fasting, from time-restricted eating to fasting-mimicking diets. So when someone is talking about fasting, these four different types are all different types of fasting regimens and they all have different benefits and different risks. So if we start with prolonged or extended fasting, typically this could include not having any calories for more than 24 hours, but it's typically reserved for longer fasts that are multi-day. Intermittent fasting often refers to alternate day fasting, where you eat one day and fast another. Or some people even use intermittent fasting to describe the 5-2 model, meaning that you would eat for five days and then fast for two.
Speaker 1:The term intermittent fasting is often confused with time-restricted eating or tiare, and that simply refers to eating within a specific daily window, like, for example, you eat only from 10 am to6 pm and then, in terms of tiare, we have early tiare or we have late tiRE. Early TRE would simply mean that your eating window is earlier in the day. For example, you stop eating at 4 pm and late TRE late time-restricted eating could refer to skipping breakfast and eating from noon to 8 pm, for example. Noon to 8pm, for example. We also have fasting mimicking diets or FMDs. These are diets that are very low in calorie and that mimic fasting biology and are used for cancer treatment, weight loss and to lower inflammation. Each of these different types of fasting regimens have different effects, different pros and cons, so let's break them down one by one. Now, across the board and across all fasting regimens, studies show reduced body weight, improved growth hormones, improved autophagy, improved glucose tolerance, better insulin sensitivity, lower blood pressure, lower cholesterol, lower fatty liver, improved gut function, improved inflammatory markers and even better improved metabolic health, independent of weight loss. But not all fasting styles are equally sustainable or equally beneficial. Intermittent fasting, which often refers to alternate day fasting, or 5-2 methods, often show weight loss. But let's be clear if calories are the same, this type of fasting does not lead to more weight loss than calorie restriction. For some people, intermittent fasting is simply a more convenient way of cutting calories, and if you want to lose weight, you either cut out calories or cut out hours of the day where you're eating them, or some people will cut out specific food groups. Now, alternate daily fasting may be better for preserving muscle mass and bone mass, but studies also report increased LDL cholesterol, sometimes by up to 10%. So this needs to be considered if you're already at higher cardiovascular risk. And compliance is also lower when we compare alternate daily fasting to time-restricted eating. So it may have benefits in terms of weight loss, but not more than the equivalent in calorie restriction, and it may even come with some risks of increasing LDL, but may be better for preserving muscle mass and lean mass. Now, TRE, or time-restricted eating, is probably the star of the show, and TRE limits when you eat, not what you eat and not how much you eat. It's about eating inside of a eating window, so, for example, we can have early TRE, where your eating window is at the beginning of the day, or late TRE, when your eating window is at the beginning of the day, or late TRE, when your eating window is at the end of the day. The most common windows are 12-12, so 12 hours of eating and 12 hours of fasting. Some windows are 14-10 and some are 16-8. And the early TRE, where the eating window ends before 5pm, typically seems more beneficial than late TRE, and 75% of studies show that early TRE improves blood glucose control. Some even suggest that TRE may reduce blood pressure by improving sodium excretion. In circadian biology matters, melatonin reduces insulin response, so eating late at night might cause higher blood sugar from that same meal when compared to if you would have eaten it earlier in the day. So it ends up that fasting is simply an umbrella term and can refer to a lot of different eating patterns.
Speaker 1:Prolonged fasting is different from intermittent fasting, which is different from time-restricted eating and fasting-mimicking diets. They all have different benefits, but they also carry different risks. Some are more sustainable than others. Carry different risks. Some are more sustainable than others. Some help with metabolic disease and weight loss, while some will increase the risk of losing muscle mass. Most people care about fasting because they want to lose weight, but in terms of weight loss the benefits of fasting don't seem to be superior to normal calorie restriction. Without fasting, an early TRE, when your eating window ends before 5pm, is more in line with your circadian rhythms and seems to have the best metabolic benefits.
Speaker 1:Now what you need to consider if you are fasting for more than just weight loss, is the quality of your diet during your eating window. Now, yes, you will lose weight and there will be benefit through weight loss if you are overweight, but what happens if your diet is of very poor quality? The chances that you're going to hit 18 mg of iron or 1000 mg of calcium or 400 milligrams of magnesium. If you're eating ultra-processed food during your eating window, the odds of all of these nutrient goals being met are quite low. So I see people fasting for weight loss while eating very poor diets.
Speaker 1:Now what happens to these patients?
Speaker 1:As they put themselves at risk of nutrient deficiencies?
Speaker 1:But, most importantly, they're probably not eating 1.2 to 1.6 grams of protein per kilogram per day and they're risking their muscle mass.
Speaker 1:So what happens is that these people, they do lose weight, but they lose muscle, and with muscle loss comes a decline in your BMR, your basal metabolic rate. It will cost less energy to exist as a smaller person. So when you start eating again, if you have not changed your eating habits or your lifestyle, your basal metabolic rate will be lower and you'll just gain the weight right back. So just be mindful that if you're fasting for anything else than inflammation and longevity and cancer risk and you're fasting specifically for weight loss, make sure that your diet is dialed in, because if not, you may actually blunt any benefits that come with longevity and cancer and inflammation if you're eating a crap diet. Now one could argue what would be the benefits of fasting if you're going to undo all of these benefits by eating a pro-inflammatory diet that's deficient in fiber and increases cancer risk? So that's exactly what we're going to be diving deeper into in part two so some people aren't just fasting for weight loss.
Speaker 1:Some people are fasting for inflammation, for longevity, to reduce cancer risks, and in part two we'll talk about all of these things, including some of the risks that we need to be aware of. So for all of you who are using fasting for its anti-inflammatory benefits, I can reassure you. Fasting does lower inflammation through multiple mechanisms. Growth hormone will surge not just during deep sleep but also during fasting, and this stimulates repair. Time restricted eating has been shown to lower ghrelin levels, which is the appetite stimulating hormone. It also decreases inflammatory markers like CRP and IL-6. And in fasting, hunger doesn't always increase, especially with time-restricted eating. The body adapts, so people who fast more often find it progressively more easy to sustain.
Speaker 1:Now for those of you who fast for longevity, we do have rodent studies showing that even a 10% calorie restriction can extend lifespan, and that's probably because of a process called autophagy. Now, autophagy is our cellular cleanup system and it's enhanced by fasting, by exercising and by restricting calories. So fasting isn't magic, it's just a way to make calorie restriction easier for some people. We even have insights from studies like meta-analyses that have looked at this, and the increase in autophagy seen during intermittent fasting is about the same as during the equivalent calorie restriction, so fasting is a tool that makes calorie restriction more easy for some people, but not this magical entity that magically increases autophagy.
Speaker 1:Now I've also had patients ask me about fasting and cancer. Now this area is still emerging. It's not well studied, but it is promising. We know that fasting reduces insulin, glucose and IGF-1, all of which are associated with cancer growth. Dr Walter Longo has published on fasting and cancer and he has a theory called differential stress resistance theory that proposes that fasting will protect healthy cells while making cancer cells more vulnerable to chemotherapy. But again, we need to be careful because prolonged fasting or full fasting can increase the risk of cachexia or dangerous weight loss. That is often seen when you're battling cancer and that's why, in clinical trials, fasting-mimicking diets are preferred. Typically, these patients will go on very low-calorie diets that mimic fasting and stay on them for about five days and then go back to a normal diet for about a month. The studies we have on these types of diets do show benefits in terms of increasing responsiveness to chemotherapy.
Speaker 1:It's important to never fast around chemo without clinical supervision. We know that cancer patients are typically losing weight, losing muscle mass. They have trouble eating, so it's very important to talk to your oncologist and to be followed by a registered. Now it's important to consider that there are many risks and red flags when it comes to fasting. Fasting is a stressor. Now that can be good in the right dose. Don't overdo it Because if you do, you risk electrolyte imbalance, brain fog, mood changes, refeedinging syndrome, muscle and bone loss. I had a patient who went on a on a prolonged fast and took diuretic medication for her blood pressure and had life-threatening hypokalemia, which is a condition that's described as very low potassium inside of your blood and that means you have very low potassium inside of your cells and that could cause, like heart rhythm disturbance and muscle weakness and cramping and neurological symptoms that can threaten your life. So if you take blood pressure meds or glucose lowering medication or have a history of eating disorders, please fast under medical guidance. Now, out there online you can find a lot of confusing information, but out here in the real world, there are certain fasting regimens that work best.
Speaker 1:Now I use fasting in my life and so I need to keep it practical. It needs to fit my busy schedule, needs to fit my goals and it cannot negatively impact athletic performance. So here's what I recommend, based on the evidence, but recognize that these fasting regimens may not fit your needs. Now, if you're going to consider fasting, I would suggest consider early, time-restricted eating. It's simple. It just means finish eating by 5 or 6 pm and try not to eat after supper. This basically aligns your feeding or your eating with your circadian rhythm, and we know that circadian aligned eating will improve blood sugar control, blood pressure and fat metabolism.
Speaker 1:Now other people would benefit from FMD or fasting mimicking diets. This is basically a pattern of five-day cycles, monthly or quarterly, especially in those looking to improve metabolic health. You go on very low-calorie diets that are low in protein, are low in protein, that prioritize plant protein and nutrient-dense plants. You eat this way for five days and then, a few months later, or a few times a year, you repeat that cycle. Regardless of the fasting regimens that you choose, always consider front-loading your calories, and you may have heard this before eat breakfast like a king, lunch like a prince and dinner like a pauper. Now, final words, you don't need to fast perfectly, you just need to do what works for your body and your life.
Speaker 1:Fasting isn't magic, but it's a powerful metabolic tool when it's used wisely. It can improve blood pressure, blood glucose, control, cholesterol. It can help simplify calorie restriction. It can help you lose weight. It improves autophagy, but not more than the equivalent calorie-restricted diet. So fasting is not magical. It is a tool. You can pair it with good sleep, good movement, connection and plant-based nutrition, because you need to have a healthy diet inside of that eating window. If you fast to lose weight and you do not eat a healthy diet, you risk metabolic disturbances and you probably negate any benefit that you had from the fasting. And in people that go on crash fasting regimens that are very severely calorie restricted, they tend to lose muscle mass. When you lose muscle, your basal metabolic rate goes down because it basically takes less calories to exist at rest and then when you start eating an unhealthy diet again, you regain the weight and undo all of the hard work you had done. So fasting is a tool.
Speaker 1:I prefer either fasting, mimicking diets or early TRE. That's the way that is evidence-based to improve metabolic function, lose weight, increase autophagy, and for me it's just simply more practical. It fits in my life and it doesn't negatively impact my training, my workouts, my runs or my ninja competitions. The most important thing is to simply find a fasting regimen that works for you. Cool Right on.
Speaker 1:I hope that this has cleared up some of the confusion behind fasting. Remember that fasting is an umbrella term. There are different fasting regimens, all with their individual pros and cons. Some are more sustainable. Some will fit your needs and your desires. Choose the one that's right for you. But if you decide to embark on a fasting journey, make sure to talk to a healthcare provider about it, because there are legit risks that come with fasting Right on. Thanks so much for tuning in. I hope you've learned a lot. We'll see you in the next episode, peace. Hey, everyone, go check out my website plantbaseddrjulescom to find free downloadable resources, and remember that you can find me on Facebook and Instagram at Dr Jules Cormier, and on YouTube at Plant Based Dr Jules.
