Healthy Eating & Eating Disorders - Anorexia, Bulimia, Binging

**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 are going to talk all about healthy and disordered eating. And indeed, we are going to talk about clinical eating disorders, such as anorexia, bulimia, and binge eating disorder, as well as some other related eating disorders. However, before we get into this material, I want to emphasize that today's discussion will include what it is to have a healthy relationship with food. We are going to talk about metabolism. We are going to talk about how eating frequency and what one eats influences things like appetite and satiety, as well as whether or not we have a healthy psychological relationship to food and our body weight and so-called body composition, the ratio of muscle to fat to bone, et cetera. So as we march into this conversation, I like to share with you some interesting and what I believe are important findings in the realm of nutrition and human behavior. I know these days many people are excited about or curious about so-called intermittent fasting. Intermittent fasting is, as the name implies, simply restricting one's feeding behavior, eating, to a particular phase of the 24-hour or so-called circadian cycle. Other forms of intermittent fasting involve not eating for extended periods of time, for entire days, or some people will extend to two days or three days, typically, and hopefully, they will drink water during those times, sometimes referred to as water fasting, which means that they are ingesting fluids, and hopefully, they are ingesting electrolytes, such as salt, potassium, and magnesium as well, because while one can survive for some period of time without ingesting calories, it is extremely important to continue to ingest plenty of fluids and electrolytes. And the reason for that is that the neurons of your brain and body that control your movements, your thoughts, clarity of thinking in general, et cetera, is critically dependent on the presence of adequate levels of sodium, potassium, and magnesium, the electrolytes. And that's because neurons can only be electrically active by way of movement of particular ions, which include things like sodium, potassium, and magnesium. So without those, you can't think, you can't function, and it actually can be quite dangerous. So why all the excitement about intermittent fasting? Well, a lot of the excitement relates to work that was done by a former colleague of mine down at the Salk Institute for Biological Studies in San Diego named Sachin Panda. Sachin's lab identified some very important and impactful health benefits of restricting one's feeding window to particular times within the 24-hour cycle, or even to having extended fasts that go for a day or two days or maybe even three days. What they saw was an improvement in liver enzymes, an improvement in insulin sensitivity, which is something that is good. It means that you can utilize the calories and the blood sugar that you happen to have. Being insulin insensitive is not good and is actually a form of diabetes. What Sachin's lab and subsequently other labs showed was that restricting one's feeding window to anywhere from four to eight or even 12 hours during each 24-hour cycle was beneficial in mice. And some studies in humans have also shown that it can be beneficial for various health parameters. However, the excitement about intermittent fasting seems to be related to the foundational truth about metabolism and weight loss and weight maintenance and weight gain, which is that regardless of whether or not you intermittent fast or whether or not you eat small meals all day long or you eat one meal in the evening and snack up until then, it really doesn't matter in the sense that the calories that you ingest from whatever source are going to be filtered through the calories that you burn by way of exercise, basal metabolic rate, which is just the calories that you happen to burn, just being alive and thinking and breathing and your heart beating, et cetera. And the reason why many people prefer intermittent fasting to other forms of, let's just call it what it is, is diet or nutritional framework, is that many people find it easier to not eat than to limit their portion size. And here I'm not talking necessarily about eating disorders, I'm talking about the general population. So I think that's one reason why there's so much excitement about intermittent fasting. Now, within the context of intermittent fasting on a circadian time scale, once every 24 hours, you generally find two categories of people. People who prefer to not eat in the morning, either because they are not hungry in the morning or because they find it relatively straightforward to just drink things like coffee or water, et cetera, and push their feeding window out to noon or 2 p.m. or 3 p.m. And then they'll eat between, say, 1 p.m. and 8 p.m. or 9 p.m. It depends on the individual. Other groups of people find that they are very hungry when they wake up in the morning. They don't feel well if they don't eat breakfast. And so they prefer to eat early in the day, but then they limit their feeding window such that they cut off their food intake or stop ingesting any calories of any kind somewhere around 5 p.m. or 6 p.m. et cetera. So the duration of the feeding window has not been broken down into the kind of nuanced type of information that one would really want, at least not in human studies saying, well, a six hour feeding window or an eight hour feeding window is ideal. It really is going to vary based on lifestyle and circumstances. For instance, some families really want to eat dinner together every night. So do you want to be the person that's sitting there watching everybody eat because you're fasting from 5 p.m. onward? I don't know. That's an individual difference. What you can start to identify, however, is that people tend to fall into either one category or the other. People who prefer to skip eating in the morning or people that prefer to or manage to skip eating in the evening. And there has been no evidence thus far that one is better or worse, at least in terms of weight loss or overall health parameters. Now, you could imagine that some people might eat breakfast and dinner. And indeed, I have several, many colleagues, in fact, who just choose to skip lunch because they're busy during the day. They eat breakfast and dinner. That doesn't afford the long fast associated with sleep. What do I mean by that? Well, if you went to sleep at 11 p.m. and you wake up at 6 a.m. by extending your fast until 1 p.m. in the afternoon, you get quite a long period of no ingesting any calories. Whereas when you don't eat during the middle of the day, you are getting a fasting period that's probably anywhere from four to seven hours, but it's not linked to the longer fasting period of not eating while you are asleep. Because most all people, and I want to emphasize most, do not eat while they are asleep. But we are going to talk about an eating disorder that does exist where people actually eat in their sleep. I know it sounds pretty wild, but indeed, that eating disorder does exist and has a very interesting underlying mechanism. So why are we talking about this? And in particular, why are we talking about this during an episode that includes a discussion about eating disorders? The reason is nobody, not the government, no nutritionists, no individual, no matter how knowledgeable they are about food and nutrition and food intake, can define the best plan for eating for any one individual. I'm going to repeat that. Nobody knows what truly healthy eating is. We only know the measurements we can take. Liver enzymes, blood lipid profiles, body weight, athletic performance, mental performance, whether or not you're cranky all day, whether or not you're feeling relaxed, nobody knows how to define these. And these have strong cultural and familial and socio-societal influence. So if you hang out with people that intermittent fast all day, that will seem normal. If you spend time with people that have never heard of intermittent fasting, intermittent fasting is going to seem very abnormal. Now we are going to talk about eating disorders that really fall into the category of clinically diagnosable eating disorders for which there's actually serious health hazards and even the serious risk of death. We will get to that topic. But for the time being, I want to emphasize a new set of findings that I think many people will find interesting and at least will want to consider in light of their current nutritional plan or pattern of eating, whether or not you're intermittent fasting or not. And I want to cue up an important framework for the rest of the conversation on healthy and disordered eating, which includes an understanding of thinking, decision-making, and what we call homeostatic processes, meaning regulation of things that are going on in our brain and body, and reward mechanisms. I'm going to return to that in a moment, but first I want to share with you these new findings that were just published in the journal Cell Reports, a cell press journal, excellent journal. This was a study that was performed both in mice and it included a crossover study with a human population. The human population was women, but it relates to a previous study that was also carried out in men. I'm going to simplify this study. We will provide a link to the full study so you can explore it in more detail. And if you're really excited about the results, I would encourage you to explore some of the references within that paper as well. What was the study? The study looked at giving mice or humans two meals and explored whether or not putting those meals early in the day or late in the day had an impact on muscle hypertrophy, muscle growth and overall protein synthesis of muscle. So when we eat, the amino acids from various foods are broken down and synthesized into different types of tissues. They can be utilized for energy, burned up for moving about and thinking, et cetera, or it can be synthesized. Those amino acids can be synthesized into skeletal muscle, the sorts of skeletal muscles that allow you to move your limbs.