Effects of Fasting & Time Restricted Eating on Fat Loss & Health

**Andrew Huberman** (0:00)
Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life.
I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we're talking all about fasting. And anytime we're talking about fasting, we are also talking about eating, because we all need to eat sooner or later. We're going to talk about how fasting and when we eat influences a large range of aspects of our health and wellbeing, both physical and mental. So, well, nowadays, most people are familiar with the term intermittent fasting, also sometimes called time-restricted feeding. I think most people don't really understand how that process works. It's sort of obvious that intermittent fasting, aka time-restricted feeding, involves eating at certain periods of each 24-hour cycle, or maybe even not eating for entire days, in some cases. But if you think about it, everybody sleeps eventually, and therefore, because people don't eat during their sleep, almost everybody is employing some form of intermittent fasting or time-restricted feeding. What we're going to talk about today is how particular schedules of time-restricted feeding can impact our health in different ways. And when I say different ways, I mean, we're going to talk about how intermittent fasting, aka time-restricted feeding, impacts weight loss, fat loss in particular, muscle maintenance and loss and gain, organ health, such as gut health and liver health, the genome, the epigenome, inflammation, sickness, recovery and healing from sickness, exercise, cognition, mood and lifespan. So we're going to cover a tremendous amount of information. I promise to make it all directly accessible, regardless of whether or not you have a background in biology and metabolic science or not. I'm also going to talk about a lot of tools. In fact, I'm going to discuss a number of tools during today's episode that actually make it such that you don't have to follow any feeding schedule or fasting schedule, same thing, if you think about it, in any absolutely strict regimented way. Meaning, if you were to only eat during an eight hour period of each day, most of the time, but then occasionally eat across a 12 hour period of the day, in theory, that could actually have pretty serious detrimental health effects. And yet there are things that you can do to attenuate those negative effects. In fact, there are things that you can do and or take that can make it as if you did not eat at all. And so we'll discuss what those tools are. And in many cases, for sake of health, weight loss, and performance, making the body think that it did not eat at all can actually be quite beneficial. Today, we're going to cover mechanism and we're going to cover tools. Before we do that, I want to highlight a particular result that was published recently because it serves as a useful backbone as we wade into the conversation about fasting. This is a study that was published in the journal Cell Metabolism, a cell press journal, excellent journal. And the title of the paper is Fasting Blood Glucose as a Predictor of Mortality, Lost in Translation. And I'll explain what the lost in translation part means in a moment. But the basic takeaway of this study, and I should mention that the first author of the study is Pali Yaguru, P-A-L-L-I-Y-A-G-U-R-U, Guru. Pali Yaguru et al. The basic finding of the study is that in humans, higher blood glucose is associated with mortality. And in fact, if you look at blood glucose, resting blood glucose across the lifespan, what you find is as people age, resting blood glucose goes up. Now this is very interesting because for a long time, it was thought that metabolism actually goes down as we age. And to some extent that's true, but the reductions in metabolism are not nearly as robust as we once thought that they were across the lifespan. However, unless there's something done to mitigate the increase in blood glucose associated with aging, almost everybody experiences a gradual but regular increase in resting blood glucose that predicts mortality. Now the title, as I mentioned, is fasting blood glucose as a predictor of mortality lost in translation. And the reason that they included lost in translation in the title is that what I just told you, that increases in resting blood glucose predict mortality or are correlated with mortality is true for human beings and for non-human primates, monkeys. But the opposite is true in mice. And so I thought it was important to use this study as an example of where studies in mice often, but not always translate to humans and to non-human primates. So today I'm going to be careful to distinguish when a study was performed in mice versus in humans, because it seems that at least when discussing feeding blood glucose and other aspects of diet, as they relate to health and well-being, whether or not a study was performed in rodents or in humans can be very important. In this case, the results were directly 180 degrees opposite to one another. In other words, in mice, resting blood glucose went down and it was associated with mortality. So lower blood glucose associated with mortality, whereas in humans, higher resting blood glucose was associated with mortality. And obviously, what we're mostly interested in is health and well-being of ourselves, of humans. I'm sure there are some people out there that are intensely concerned about the health and well-being of mice, which you could imagine a few rare contexts where that's important. But obviously, most of us are interested in human health. So I'll be sure to emphasize when studies were performed in humans versus in mice. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is Athletic Greens. Athletic Greens is an all-in-one vitamin mineral probiotic drink. I've been taking Athletic Greens since 2012, so I'm delighted that they're sponsoring the podcast. The reason I started taking Athletic Greens and the reason I still take Athletic Greens once or twice a day is that it helps me cover all of my basic nutritional needs. It makes up for any deficiencies that I might have. In addition, it has probiotics, which are vital for microbiome health. I've done a couple of episodes now on the so-called gut microbiome and the ways in which the microbiome interacts with your immune system, with your brain to regulate mood, and essentially with every biological system relevant to health throughout your brain and body. With Athletic Greens, I get the vitamins I need, the minerals I need, and the probiotics to support my microbiome. If you'd like to try Athletic Greens, you can go to athleticgreens.com/huberman and claim a special offer. They'll give you five free travel packs plus a year's supply of vitamin D3K2. There are a ton of data now showing that vitamin D3 is essential for various aspects of our brain and body health. Even if we're getting a lot of sunshine, many of us are still deficient in vitamin D3. And K2 is also important because it regulates things like cardiovascular function, calcium in the body, and so on. Again, go to athleticgreens.com/huberman to claim the special offer of the five free travel packs and the year supply of vitamin D3 K2. Today's episode is also brought to us by Element. Element is an electrolyte drink that has everything you need and nothing you don't. That means the exact ratios of electrolytes are in Element, and those are sodium, magnesium and potassium, but it has no sugar. I've talked many times before on this podcast about the key role of hydration and electrolytes for nerve cell function, neuron function, as well as the function of all the cells and all the tissues and organ systems of the body. If we have sodium, magnesium and potassium present in the proper ratios, all of those cells function properly, and all our bodily systems can be optimized. If the electrolytes are not present and if hydration is low, we simply can't think as well as we would otherwise. 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