Eating in Circadian Rhythm - J A Conversations with Dorothy Sears (Time-Restricted Eating)




In this instalment of the J A Conversations series I had the chance to have a great conversation with Dorothy Sears, Professor of Nutrition at the Arizona State University College of Health Solutions. Our conversation focuses on eating in sync with your natural circadian rhythm and the benefits that can bring about. We also discuss some of the negative effects that can occur when we consume food outside of our circadian rhythms. We also touch on light exposure and its role in activating the suprachiasmatic nucleus and suppression of melatonin.


Transcript:

Josh

Welcome to the next instalment in the J A conversation series. My name is Josh, and I'm the founder of J A A fashion brand taking a holistic approach to sustainability. In this series, we'll be talking to people who are moving things forward in their chosen field, or just have great information to share, whether that be a fashion, arts and culture or health and well being in this instalment I had the chance to have a conversation with Dorothy Sears, Professor of Nutrition at the Arizona State University College of Health Solutions. Our conversation focuses on Circadian Rhythm, and Time Restricted Eating.


Dorothy

All right, so I'm Dorothy Sears. I'm a Professor of Nutrition at the Arizona State University College of Health Solutions. And I also have an adjunct position at UC San Diego and the department's of medicine and family medicine.


Josh

Thank you so much for joining me today, Dorothy this is, I'm really excited to have this conversation with you and kind of get this information out to people. So yeah, I'm really, really looking forward to this one.


Dorothy

Great to be here. Thank you.


Josh

So I kind of wanted to dive into the topic of Time Restricted Eating, and how that's connected to our Circadian Rhythms. Could you explain what Circadian Rhythm is and, and kind of how that works and how that's like a cycle for the body?


Dorothy

Sure. So Circadian Rhythms is something that almost every living thing on the planet has, which is a 24 hour cycle light, dark cycle, dictated by the sun when the sun's up when the sun's down. And the body or the cell, depending on what critter you're talking about, is going to be performing different activities, biological activities, biochemical pathways, sometimes different behaviours, depending on whether it's light or dark outside. And so in every cell, there is actually a protein system that regulates this, and it has a circadian pattern to it of this 24 hour cycle. So it goes through these cycles. And so in some parts of the body, we have proteins that are expressed during the daytime. And sometimes we have other proteins that are expressed during the night time. And this change in protein expression dictates what kind of biological pathways that can go on. And it influences things like nutrient metabolism, sleep, and other behaviours, physical activity, what the best time to do physical activity and those kinds of things.


Josh

Yeah. So when we, when we first wake up and light hits our eyes, the clock starts and genome expression starts happening.


Dorothy

Yeah. if I could you bring up a really important point that I should say, and that is that I mentioned the light dark, but you mentioned when we get up in the morning, the light hits our eyes. So light, going through our eyes and into a part of the brain called the suprachiasmatic nucleus. This is where that central clock is, and it's really driven by that light signal. There are other clocks that are driven by let's say, nutrient signals and other parts of the body. But our primary or master clock, as it's called, is in the brain and driven by light.


Josh

Okay, so that suprachiasmatic nucleus, that's, that's like a sensor or it goes off when Okay, when the light hits it,


Dorothy

then that clock in the brain is talking to other clocks throughout the body.


Dorothy

But that's where that that master clock is. So even, you know, the liver has a clock, our skin has a clock, and they're not all doing exactly the same thing, of course, but they are talking to each other through both through nerves that are connecting the brain to these other parts of the body, but also things that get secreted into the circulation. Those are all part of the kind of crosstalk between these different parts of the body.


Josh

Yeah, yeah. And so, you mentioned that different parts of the body have their own clock that the liver for example, how do those clocks get started?


Dorothy

So the clock the definitely the suprachiasmatic nucleus, the SPN is talking to the liver clock, but once we eat food, the nutrients that are getting into the blood, they are also talking to core clock pathways in the liver. And so this is why it is really important that the the suprachiasmatic clock, the master clock is in synchrony with the other clocks.


Dorothy

So our bodies are designed, for example, to process nutrients the most effectively during the day, primarily in the morning and the midday and then as the circadian clock is ticking and the liver let's say, then our bodies are less able to process nutrients in the night. So when you have food at night, and it's dark, you're synchrony between these clock systems is, is askew, you have the brain thinking, hey, it's nighttime, I'm doing these things. And then you have the liver getting the nutrient signals, saying, Wait a minute, is it daytime? I'm getting food


Josh

its confused.


Dorothy

Yeah, It gets confused


Josh

Yeah, yeah. So once you take your first bite of food so does drinking count I guess if you have a sip of water, you're still fasting. But any kind of any enzymes you have to break down or anything like that the clock starts.


Dorothy

So there's differences of opinion about, you know, fasting, and I don't know that anybody's ever looked to see whether actually biologically drinking water impacts the Circadian Rhythms. But definitely calories do so things with some kind of nutrient. They do. So caffeine, also, there's, you know, there's debate on biologically, whether caffeine and setting the clock tends to impact the Circadian Rhythms.


Dorothy

However, when. So for the folks that are the biological mouse model, scientist, and they're looking at how things work, they're thinking about these things. I like to think about what are people doing in the real world? So if we're thinking about fasting, if you can fast, a little longer in the morning, and that a black coffee helps you do that?


Josh

Yeah,


Dorothy

I say go for it. If I don't get my coffee in the morning, get a headache.


Josh

Yeah, yeah. So maybe delaying your breakfast a little bit. Could be could be beneficial.


Dorothy

I think you have to tie it all together in the 24 hour clock. So I think it's not just about delaying breakfast. But it's about having a period of time during the night time, where you completely sustained from caloric intake. And so it seems, from the data that if you're stopping your food intake, or greatly reducing your food intake earlier in the evening, somewhere, we don't know what the magic time is, but five, between 5pm and 8pm. And then abstaining from food until the next day, in our, in our population studies, this looks like 13 hours of fasting 12 to 14 hours, there's a good range of fasting time that's associated with health benefits. So if you stop eating at 6pm, and you want to go 14 hours of fasting, that means you don't eat till eight, you might wake up at six. Yeah, want a cup of coffee, you could have a cup of coffee, but I don't think that skipping breakfast and going fasting all the way into the lunch period. I think that perhaps its own problem.


Josh

Okay Yeah. I guess yeah, you might end up eating later as well. If you do that, you might not start getting hungry for dinner until a lot later.


Dorothy

Right? Well, and there are other things too, like, you know, and again, these are things that are kind of educated guesses, they haven't been formally this, what I'm going to tell you now haven't been formally tested. But if you're fasting for a particularly long period of time, and then your day starts, you're going to go commute to work, you know, COVID aside, we're going to get in the car drive to work. You know, if you've been testing for a long period of time, I suspect and I experienced this myself, that if I have some kind of scary experience a fight or flight type of experience, that then the blood glucose drops because you've been maintaining it, your body's very good at maintaining your glucose level. But when you have an acute challenge, a stressor that can drop your glucose and we know that that is not good for the body long term when you're experiencing that. So I suspect that that's one reason why skipping breakfast and waiting for a long period of time just is not overall good for the body.


Josh

Yeah, okay. You've dropped your glucose level. Okay. Yeah. And so that will bring about like a cortisol release or and that's bad or exactly, exactly those fight or flight hormones.


Dorothy

Well, cortisol has a circadian rhythm, but epinephrine and norepinephrine that yeah, those are the things they tell your body we got to run so the glucose in your blood gets taken up by the tissues. So you can energise your muscle and your tissues and you could run from the lions. And now your body will respond very quickly and deliver Your brain will find that the glucose now is low in the bloodstream. So then the liver starts to pump out glucose. So this period of a little bit of hyperglycemia doesn't last very long. But it triggers this stress response in the body is that I think on the long term is not a good thing. So I don't like to advise people to fast for longer than about 14 hours. Because we find that that's helpful. I don't know that there's any additional benefit to fast longer than 14 hours, and then if you're trying to fast for 18 hours, then you're going to run into likely you're going to run into those periods of risks that I think are a little bit risky.


Josh

Yeah, exactly.


Dorothy

Yeah. Now, some people will start their fast at like two o'clock in the afternoon. So then they're going to have breakfast at 6am. And they're not going to have that window of time of which they can be exposed to some stress, stressful experience. But you know, when I think about intervention, we want to think about what is real life. And people, people have dinner with their families, they go meet people for dinner, when COVID isn't around. Stopping eating at two o'clock is is socially it doesn't fit in, it doesn't fit into our social structure very well. So yeah, I like to think about really practical ways of controlling the timing of your food intake, and your fasting that fits in the daily life.


Josh

Now, how would you recommend people manage that? Because obviously, you want to try and have, like you were saying a decent amount of gut rest at night. So not eating too late. But there are those social pressures I don't know maybe go out for dinner and see friends like, how do you? Yeah.


Dorothy

Well, there's a really interesting mouse study, done in Satchin Panda's lab at Salk, where they looked at doing a time restricted feeding study in the mice. And I found this to be very effective for controlling obesity and metabolic dysfunction or, you know, when your metabolism wasn't working, right. And one of the folks in the lab said, Well, what if the mice could eat whenever they wanted on the weekend, but only Monday through Friday, we do the time restricted feeding.


Josh

okay.


Dorothy

And the mice had the same metabolic benefit as if they were doing it every day. So as a, as a clinical researcher, I find this very exciting, because, you know, let's say on the weekend, you want to go out with your friends and have a late dinner or where you want to have a glass of wine at nine o'clock at night, you know, it seems like if you have a day, or maybe even two days off a week that this is still going to be okay, in the long term. And I don't think of this eating pattern as a diet or something I'm going to do for a short period of time. I try to do it all the time.


Josh

Yeah.


Dorothy

It's a long game.


Josh

Yeah.


Dorothy

So a day off one or two days off a week. It seems okay. That it might be okay. For humans. It's definitely okay for mice. And so this is another thing that needs to be tested, you know, in control studies,


Josh

So kind of, yeah, so treating it like a lifestyle, and then one or two, one or two dips here and there isn't gonna do too much too much damage. And so, eating kind of in the first half of the day is important. Because we're most insulin sensitive at that point.


Dorothy

Yeah, exactly, exactly. We are most insulin sensitive during the morning and the midday and then our bodies become progressively less sensitive to the hormone insulin throughout the day. Even the tissue the pancreas that secretes the insulin is on a circadian clock, so you don't have as much insulin secretion at night. So it doesn't work as well on the target tissues and it also doesn't get secreted as much. So the negative outcome of that is that you get a higher glucose concentration in the blood after your dinner meal. Then you would having the same meal at breakfast or the same meal at lunch. And then you know, the later you go into the night the worse it gets. Essentially, the body is shifting gears the body is saying I want to start growing now I don't want to start with I don't want to be receiving nutrients. So things like growth hormone are stimulated in a pulsatile fashion, but the pulses get larger in the night. And growth hormone and insulin work against each other. They don't like to be in the same place in the same sandbox. And another hormone to that secreted at night is melatonin and that's helping us sleep and also suppressed by lights and melatonin. It gets secreted in the nighttime and melatonin and insulin also counteract each other. So, you know, these are some kind of kind of circadian hormonal pathways that are really controlling not just our ability to process nutrients But our sleep quality, alertness and things like that.


Josh

So yeah, you mentioned that can affect your sleep quality. And so what are some of the detrimental effects of kind of eating late into the evening slash night? What are those?


Dorothy

So, quite a bit. So we we just to touch on sleep a little bit, this has not been formally tested. But this is something that we have some ongoing studies where we're looking at sleep. But we know in some interventions that people just when they're asked about sleep, they self report that they get better sleep quality when they're doing a time restricted feeding or prolonged, nightly fasting regiment. I even have friends that I have told about this pattern of eating, and I didn't say anything about sleep, and then they come back to me and say, Oh, my God, I was sleeping so much better. So I think this was going to be a really exciting area of research to come. We know that there's a lot of health, negative health outcomes that are associated with eating at night. Disease wise, so for example, higher incidence of breast cancer, prostate cancer, cardiovascular disease, obesity, type two diabetes, as well. And our controlled studies where we're actually measuring the chemicals in the blood and blood pressure, we know that eating at night is associated with higher blood pressure, higher insulin and higher glucose and a larger waist circumference, which we don't want that.


Josh

Yeah, yeah, exactly. And so then the problem is, like you said, Your, your body's shifting into that kind of growth mode and repair mode at night, and you've got a whole heap of sugar coming in or glucose, that it needs to deal with it not quite sure how to do that, or, or, or that glucose gets left and turns into fat. Is that correct?


Dorothy

That's a good question. I don't know whether conversion of glucose into fat is more efficient at night than it normally is. But I do know that if the glucose is hanging out in the blood for longer, you know, normally when we eat a meal, the glucose molecules that come from that meal Are you know, they enter into the bloodstream, and then the hormone insulin is going to tell the tissues in our bodies to take up the glucose, get it out of the blood. And so at night, this is not happening as effectively. So the glucose concentrations stay high in the blood for a longer period of time while insulin is trying to do its job. And what happens when the blood glucose is high is that you get kind of a sugar coating of proteins that are in the vasculature in your blood vessels. Even haemoglobin, and our red blood cells get sugar coated and so there's an actual clinical biomarker called haemoglobin A1c. And haemoglobin A1c is what doctors look at to see if people who have diabetes have been controlling their glucose. Because the more glucose molecules on the haemoglobin, the worse their glucose control has been.


Josh

Okay.


Dorothy

So you can imagine a protein that has, you know, proteins are very, it's very important that their structure is maintained. If now the structure of your protein is getting peppered with glucose molecules around it, it's not going to fit or function as well as it normally would, because of these are called glycation reactions. And they're permanent. So once that protein is recycled, you know, it sticks around. So haemoglobin, A1C is a clinical biomarker, but there are all kinds of other proteins, like I say, the lining of the small blood vessels that get damaged. And so for example, in type two diabetes, when we think about the complications of type two diabetes to the retinal, loss of sight, loss of nerve sensation in the extremities, the fingertips and the toes, this is a lot because this is primarily due to those glycation reactions that are inhibiting the normal functioning of those little blood vessels in your retina or whatnot, in the kidney too. So the more we can control, improve glucose control with the fasting at night, eliminating eating at night, or at least late at night. This should reduce risk for diabetes and related comorbidities like cardiovascular disease and dementia


Josh

And so yeah, Dementia as well. Okay. So are those reactions causing inflammation and that's where things are going wrong. Or you're just damaging the protein and it doesn't.


Dorothy

Glucose high glucose in the blood can cause what's called oxidative stress. So the oxidative stress creates very reactive molecules that can trigger inflammation. So absolutely. That is also happening.


Josh

Yeah, yeah. Okay, and so somebody who maybe has a chronic disease or diabetes, how can they use time restricted eating to help help that?


Dorothy

So, for people with type two diabetes, I think, one, two, first consult your physician, let them know what you want to do. People have been trying all kinds of regiments with type two diabetes patients. I think that just either eliminating food intake at night, let's say, you know, no food after 7 or 8pm will help a lot. In our studies, we show that consumption of less than 30% of your calories at night, is associated with better health measures, for example, the blood glucose, or the blood pressure and so forth, versus people who have more than 30% of their calories at night. I think this gets to another social issue is that typically in the Western world, we, our biggest meal is at dinner.


Josh

Yeah, absolutely.


Dorothy

So I think part of this is a reframing of social habits and thinking about, Okay, I need to eat a bigger breakfast and lunch and have a small, small dinner. So I think people with type two diabetes could definitely benefit from from that. There have been published so far, very, a relatively few number of what we call randomised controlled trials of time restricted feeding, or prolong nightly fasting. There are some new big trials funded right now. And I just have the new one funding from NIH myself. So this, this data will get better. But some studies have included people with type two diabetes, or pre diabetes, and so far, there doesn't seem to be any safety concern in these populations. very promising.


Josh

Yeah, yeah. And you mentioned pre diabetes. What What is, what is that is that you kind of that the A1c you mentioned is that like, you can see the glucose is higher, it's starting to get higher, and then


Dorothy

That's correct. Yeah. So both the fasting glucose is high, but not in the clinical classification of type two diabetes. You know, these changes happen gradually. So it's early on. And then also the haemoglobin, A1c is also elevated. So there's kind of a cut off for diabetes. So if you cross over the line, you have diabetes, but before then there's kind of a range that they call pre diabetes.


Josh

Okay. So if you if you did have pre diabetes, and you caught it early, and you tried this, you could reverse that potentially, and not cross over the line.


Dorothy

So I think that you could at least slow the trajectory and improve that haemoglobin, A1c, we know that a lot of different lifestyle interventions can delay the onset of type two diabetes, unfortunately, there's a strong genetic component for risk of type two diabetes. So some folks are probably going to get diabetes later, some day, but the more you can delay the onset, the better off for your long term health. So I think everybody, everybody could benefit from just trying to think about ways that can control their glucose. And the nice thing about the fasting regiments and time restricted feeding is that you don't have to read labels to do it. You just look at the clock.


Josh

Yeah, yeah, exactly. And so that's another question, I guess is how much does diet quality play apart? And what you're eating? Yeah. Or is it more about just getting within those timeframes?


Dorothy

Yeah. So this is also really interesting question. And the NIH has just released a bunch of funds for research. People are applying for these now to look at these more intricate questions. So if I'm doing time restricted feeding, can I still eat McDonald's hamburgers, you know, in the mouse, this works in the mouse, so in the mouse, and they're eating very high fat Chow, this high fat pellets in their cage. And if you just do the time restricted feeding they the metabolic benefit is enormous and you don't change the food quality. We don't know whether it's going to work in humans or not. And also, it may be that the mice, when they're eating for only eight hours, they still eat the same number of kilocalories. So they kind of catch on like, Oh, I only get food for eight hours. So I'm going to eat all the calories. But it's interesting because in humans, it appears that in some people, they tend to eat less when they're doing the time restricted feeding. And so another Circadian Rhythm is that is the behaviour of food intake. So we normally have a satiety signal when we feel full, and some of those satiety signals are on Circadian Rhythms so they don't work as well at night. So if you're eating at night, you might eat more calories at night then you would, because you're not getting that satiety feedback to the brain.


Josh

So you don't get that feeling of being full or you don't get that message. Usually if you just keep going.


Dorothy

Okay, exactly. Yeah, I learned this recently. So when your stomach enlarges, when the food gets in there, your stomach enlarges that's stretching. It's like just a physical stretching signal that is connected to some nerves that go up to the brain, and they tell the brain, hey, the stomach and stretching and the brain says, Hey, okay, we're full stop eating. That is under circadian control. So that signalling doesn't work as well at night, which explains maybe why people when they're snacking at night, they might eat more than if they were snacking in the afternoon.


Josh

Yeah, yeah. I guess the gut isn't and the liver are not controlled by light. But obviously, like you said, the first intake of food, and then so you've got 12, you've got those 12 hours to kind of finish eating.


Dorothy

Yeah, yeah. The liver isn't detecting light directly, but it is listening to the circadian, the suprachiasmatic nucleus, which is telling us that it's light.


Josh

And then so within that, obviously, people eat kind of three times a day, roughly, but then some people kind of snack in between those times. Does that have any effect?


Dorothy

That's a really good question, too. So there is some research going on looking at the frequency of meals, if we have a lot of little meals. Is that better than having three meals? And I think the jury's still out on that. We don't we don't know. And I think what we need to layer on to that research and to the interpretation of the findings is, What time are these things happening?


Josh

Yeah,


Dorothy

Because the frequency thing, if you are eating frequently, but you're eating frequently well into the night, then that's bad, versus somebody who's eating frequently, but only within a particular frame of time that is in alignment with the circadian clock.


Josh

Yeah, yeah.


Dorothy

Well, I had one thought, too, that I wanted to tell you, so about the what type of food does it matter?


Josh

Yeah.


Dorothy

So there's a study out of Hong Kong, looking at the incidence of breast cancer in women. And so women who eat after 10 o'clock had a higher risk of breast cancer, it was a very large population. So they were able to say, Well, what if the women were eating just fruits and vegetables after 10 o'clock. And when they looked at that group, that group did not have an increase of breast cancer risk, even though they're eating fruits and vegetables after 10 o'clock. So I suspect that it will matter what you were eating at night. And I think this is very promising for shift workers, you have a very high percentage of shift, folks in the in the Western world who do shift work, and they don't really have any choice about it. It's even the international Cancer Society has described shift work as a carcinogen.


Josh

Wow,


Dorothy

Because the evidence is so strong. So what do we do for those folks? So if we can determine fruits and vegetables at work for you are good or have a salad and then have your big meal when you get home at 6am? So these kinds of questions are things that we really need to, to answer so that we can help those communities.


Josh

Yeah, absolutely. Yeah. shift workers. It's a big one, isn't it? Because obviously, their sleep is affected, and then their eating habits change. So if there is something they can eat, that's that that kind of offset some of the damage that might occur. That's amazing.


Dorothy

Exactly. And then with the shift workers, it's even more complicated than just food, right? Because they're exposed to the light, They're exposed to light at night, so their central clock in the brain is confused.


Josh

Yeah.


Dorothy

What do you do about that? And so we do have blue light blocking goggles. I actually use these myself at home after 8pm. I put them on. But you can't have a shift worker put on blue light blocking goggles, because now they'll probably get sleepy.


Josh

Yes, yeah, that melotinin kicks in


Josh

Yeah. Okay, that's really interesting. And then so does age play a part at all in kind of your resistance to some of these things? Like, if you're kind of in your late teens, early 20s, and your out partying eating late. Is that going to catch up with you? Or are you pretty resilient at that age?


Dorothy

Yeah, that's a really good question. As we age, we just become more insulin resistant. So I'd imagine that older folks will have a more detrimental effect or, eating at night will have a more detrimental effect on them, because they already have that layer of insulin resistance because of their age. So younger folks might be a little more resilient. And know and have just a really great insulin sensitivity. And so even though sensitivity is relatively lower at night, it's still pretty good for them. It'd be interesting. Yeah. To look at different age groups.


Josh

Yeah.Yeah. And you mentioned that breast cancer trial you did, and I think I saw a study where you looked at recovery rates and the likelihood of relapse in the cancer. Could you tell me a bit about that?


Dorothy

Yeah, so this was a study of the data that was generated. We analysed data from a study called the women's healthy eating and living trial. Well, so the well, participants, there are over 3000 women's breast cancer survivors in this study. And they were enrolled in, you know, either a weight loss diet, which was low, low fat, high fruits and vegetables, or, you know, control condition, and then they were monitored out over 10 years time. And during that time, they were you know, because it was a diet intervention, they were collecting data about what were they eating? What time were they eating? So we have all this, what we call timestamp data. So we were able to go back to those records. And look at Well, what time were people eating? So from all these over 3000 women, we were able to look at 30,000 food recalls, that were timestamped. And then over the period of this 10 years follow up of these ladies, they were keeping track of who got breast cancer again, or who died of cancer, died of anything. So mortality outcomes and breast cancer. And so the student who was working with us at the time, Catherine Marinac, what she was able to show was that the women who fasted for less than 13 and a half hours, had a 36% increase in breast cancer recurrence compared to the women who fasted for at least 13.5 hours. Yeah, and there was also associations with sleep for longer duration of fasting was associated with longer duration of sleep. But these are association studies, not intervention studies. So we don't know that the fasting is affecting sleep directly, or just people who fast more go to bed early. You know, we don't know.


Josh

Yeah, yeah. Yeah.


Dorothy

That was a really exciting study. And to this day, that is the only fasting The only data showing a what we call a clinical outcome associated with fasting,


Josh

Okay,


Dorothy

Clinical outcome is you get cancer or you have a heart attack or something that versus a biomarker where you're looking at haemoglobin A1c.


Josh

So it's pretty strong, strong data to say this is the likely outcome. or this is the outcome,


Dorothy

It is a strong association data. So yeah, so the best test is what we call a randomised controlled trial. So you recruit individuals, you have a control group, you have an intervention you actually change what they're doing. And so I and other folks in the united states are doing research where they're actually doing these randomised control trials. Take individuals who fast for less than 12 hours, and then increase their fasting time and how does that change their health outcomes?


Josh

Yeah, yeah. And so when do you think you'll see some of the outcomes from those trials?


Dorothy

So one of them is being conducted by Courtney Peterson at the Pennington Institute. I think she is probably going to have data in about four years. And I don't know how much COVID has delayed her. So all of us doing clinical trials have been a little bit slowed down by COVID. I think she'll have her data in about five years. My trial is just getting started. I'm collaborating with Julie Pendergast at the University of Kentucky. So we will start enrolling individuals probably in the fall. And it's a five year it's a five year overall study. So the intervention is only 12 weeks, but we will have our data five years from now essentially. So it takes a while to get the data.


Josh

Yeah, I can imagine. Yeah, . Have you seen kind of any kind of like kind of, I guess, maybe association or observation from like, cultural differences like different cultures eating kind of at different times, or anything like that?


Dorothy

I'm glad that you asked me that because I almost always get a question. Well, what about in Spain? Because in Spain, they always eat late at night, you know? And so there's a couple things. So one is that the people in Spain just to use that country as an example, they have a lot of different health behaviours than we have in the United States. So for example, they walk a lot. They use the stairs a lot, a lot more than people in the united States. So they have those kind of health behaviours. So yes, they're eating at night. But Spain also has an obesity problem. Obesity is an epidemic around the world where people have plentiful food, as long as there's no food scarcity, we have obesity. So, so Spain is not immune to that. Another health behaviour that the Spanish have is that they eat smaller portions than the United States. So yes, they're eating at night. But there are some other factors there. And then there are two studies that are really interesting that are in a Spanish population, they were analysis of data from two different weight loss trials. One was a study looking at weight loss after bariatric surgery. And one was a study just looking at, you know, reduced calorie weight loss standard. And what they said was, let's look at this data they knew when people were eating when their meals were and how big they were. So they said, well, does it matter in these populations when they eat their biggest meal? And what they found was that the women, I don't know that they're all women, the individuals in this trial, if they had their biggest meal at lunchtime, they lost more weight than the people who ate their biggest meal at dinner and this is in Spain. So the biology, I think, is pretty universal, at least at least in kind of European, Western world populations. There's some studies out of Korea and one in Japan that suggests that fasting doesn't have any benefits for those individuals. But just looking at fasting time takes away some of the assessment of whether the food intake is happening during the day or during the night, and what proportion in the day. So there's a lot of different dimensions to examine.


Josh

Yeah. Yeah. And that's interesting, what you're saying about, obviously, portion size. So for those shift workers who are eating late, as we said, maybe just reducing that portion size that they do have may help as well.


Dorothy

Yeah. Because it's a portion is smaller than that's less glucose getting into the blood, or something that doesn't have very much glucose, like, fruit and vegetables, you know, depends. As long as not a fruit smoothie, those have a lot of sugar.


Josh

Yeah don't pile that up


Dorothy

Salad, you know, some lean meat, you know, maybe, you know, that's a dietary plan that would be effective for them.


Josh

kind of limit the carbohydrate later, in to the evening. Yeah. And then, so have you seen kind of anything with people of different races or anything like that?


Dorothy

Well, again, the studies have been quite small for the intervention. In the well study. There was no Unfortunately, there wasn't a lot of racial or ethnic diversity in there. We have done a pilot study of the prolonged nightly fast, we call it pro fast, prolonged nightly fasting intervention. And we did two groups of 10 women and one group, we went to the South County of San Diego, and we enrolled lower socioeconomic status Latina women. So these are postmenopausal women, and with a different family structure than our other population, which was in La Jolla, California, predominantly white college educated, you know, until we did it, the study and both of them just to see whether it was feasible, because again, with the family and cooking dinner at night, does this work for those ladies? And can they achieve the goal which was to fast for at least 12 hours every night? And, and they were just as capable and excited about it as the women in la Jolla. In that one, it was just a trial to look at what we call feasibility, like, does this work does this work in people's lives? And so they, we saw a modest amount of weight change, but it was just a short one month intervention and the change was not statistically significant. So this needs to be replicated in larger populations, but at least the social context that we're so different, seem to not bias the efficacy, I should say the feasibility, of the intervention.


Josh

Yeah, yeah. Yeah. That's interesting. You mentioned like weight loss there. Like, is there any kind of other health benefits? So I think I read a study maybe the mice increased muscle mass. When they stopped eating after a certain time.


Dorothy

I don't know about the muscle mass one in our studies, the mice don't, we fatten them up. So they're really obese when we start. We fatten them up first. And then we split the mice into two groups. And one, they just keep eating whenever they want, which is pretty much 24 hours a day they eat. And then the other group, we only let them have the food for eight hours. So they lose a little bit of body weight in the beginning, and then they stabilise. When we looked at their fat mass, if we can look inside the mice, and we look at the fat mass, the fat mass is shrinking. And interestingly, the fat that is in the liver of those that obese mice goes away. Fatty Liver is a huge problem in the United States. And the Western world that goes along with obesity, even in young children Fatty liver is a problem. So the fact that the time restricted feeding is reducing the fat in the liver was really exciting. The insulin the fasting insulin levels go down, which tells us that the mice are becoming more insulin sensitive. So a lot of biologic a lot of metabolic biologically metabolic benefits happen. That the magnitude of that far exceeds the magnitude of the weight change. I think it gets to another thing in our society. And I think weight loss is good. But a lot of people are thinking about, oh, I want the number on the scale to get smaller. And we do and that's a good thing. But when you start a regiment like time restricted feeding, it's possible that you could be having metabolic benefit and not see a change on the scale. Or just changes that we cannot sense or we can't measure without taking a blood sample or something like that.


Josh

Yeah, yep. And, arguably, those changes are better right, You want to reduce the fat in your liver and some of the changes that you can see or notice, like better sleep and things like that, is definitely going to definitely help you recover properly and help your brain and all of that.


Dorothy

We have a small trial going on right now to see whether if the time restricted feeding will improve cognition in older adults who have mild cognitive impairment. We know that cognitive decline is associated with these high levels of glucose exposure. So people with diabetes are more likely to have cognitive decline than people without diabetes. So we are optimistic that we'll see some improvements in cognition. One of my colleagues at Arizona State, Carrol Johnson has started doing some small pilot studies and the undergrads at Arizona State so relatively young population, showing she's found some evidence that mood improves.


Josh

Okay, yeah.


Dorothy

So it's gonna be really exciting to see all the new studies that come out.


Josh

Yeah, definitely. And is that the kind of link you're saying with dementia earlier? Is that how that would happen? Like higher levels of glucose at night, and you're brains not dealing with that or clearing that away? Or?


Dorothy

Exactly, because that vascular damage that I mentioned, can be happening in the brain, and then that interferes with our ability to get oxygen to the brain and nutrients.


Josh

Okay. Wow, is there kind of any studies out there looking at maybe how this can be used for peak performance? Maybe athletes want to look at this?


Dorothy

Yes, there are a few studies looking at it, you know, they're very small. Yeah. I think there's promise, I think there's promise there. And sometimes they're kind of mixed with it's prolonged nightly fasting plus strength training. So they mix a lot of interventions at the same time. Sometimes in those designs, it's hard to determine what was the most effective factor in the results. So but I think there's promise there. Also debate on what time of day is the best time to exercise? Because we know that we know that, for example, that you know, our greatest muscle strength and cardiovascular strength, our core best coordination is in the afternoons a later afternoon. So is that when, is that when we want to exercise is that when you want to play our sport? And then the exercise scientists will say, Well, if you can get people to exercise any time of day, that's a good thing. But don't confuse people about what time of day but I know for elite athletes, of course, this is something that they might be able to capitalise on to improve their performance.


Josh

Yeah, and I think I saw another study as well. Saying something endurance was improved that the kind of the earlier people stopped eating. I can't remember this was in people in mice but the earlier they stopped eating they had better endurance the next day. Yeah, yeah. Yeah. So and like you said, finding out about the time as well would be interesting.


Dorothy

Yeah. And then is that because they got better sleep? And then they had better endurance you know? So these things are so linked. And so when we design our studies, we're trying to measure all these things at the same time. So we have people wearing, you know, wrist accelerometers, and things that we can use to objectively measure sleep time. Even, you're probably familiar with that continuous glucose monitor. This is a device that people with type one diabetes were wearing. It measures a glucose level every five minutes. And you can even have an app on your phone to measure the glucose and see what your glucose is. So this helps them keep their glucose in control, because they can see it so often, and don't have to prick their finger all the time. So now it's becoming more common for people with type two diabetes to wear these, to use these, and then also to, for researchers to use them. So if I'm asking somebody, when did you last eat, they may tell me the truth, they may not. They may forget I forgot that I had some Cheetos at 10 o'clock. But with a with a continuous glucose monitor on I can see when they have the carbohydrate, I can see that come. So I think combining these different devices, wearable devices that objectively measure our bodies, rhythms, our sleep, activity rhythms, our physical activity, the glucose, there's another device called an ibutton that you can wear it measures the skin temperature, Also circadian heart rate rhythms are circadian. We, some Fitbit and some other devices will measure this with called heart rate variability. If you have a high level of variability to the heart rate variability, this is a good thing. And also linked to endurance and performance. Yeah, so we're interested in adding that device as well. So our study participants are going to be rigged up so we can really watch them because we need to see the 24 hour patterns.


Josh

Yep. And that heart rate variability one is a interesting, would it be interesting to see how time restricted eating affects that? And, what it would it does?


Dorothy

Absolutely. Well, you know, I look at my, my sleep data every morning when I wake up, and I have a Fitbit. So I'm looking at that. And so there's a time about 4:30 in the morning, that we all have our lowest body temperature and the lowest heart rate. So I'm always looking at you know, did I did I did I have that dip? We know that people who don't have that dip have increased risk for cardiovascular disease. I'm looking at this data. And I noticed, if I do eat late at night, then my heart rate is higher way into the night. Hopefully, I still get a little bit of a dip. But you can see you can see your heart rate data is affected by the time late night food intake. Yes.


Josh

That's Yeah, that's huge as well for people to monitor that. So what kind of regiment do you do? What kind of routine Do you follow?


Dorothy

Yeah, so I try to ask for at least 12 hours every night. And I try to eat no later than eight. Yeah, very rarely eat any calories after 8pm I try to eat as early as possible. But again, it's difficult with family or with your work if you're in the office to later you know, you know, it's not always so pleasant to eat dinner in your office.


Josh

It's not nice.


Dorothy

So I try to make a note a mental note. What time am I eating? It's dinner time is 6:30 then that means you know after 6:30 I can eat but I I usually go eight hour Sorry, I'm usually fasting at least 12 hours. I also try not to go more than 14 so my goal is kind of 12 to 14.


Josh

In that window Yeah, yeah. Nice. Have you kind of seen this becoming more popular more people kind of getting in touch is the momentum around this growing are people kind of cottoning on to this or?


Dorothy

Oh definitely.Yeah, definitely. If you Google it I googled it the other day, I can't remember how many hits it was like millions of hits on Google intermittent fasting and you know, people are writing books. You know, I I think we still have a lot of things to learn from properly designed research trials about what the best regiment is. So because the mouse studies have an eight hour feeding window and then 16 hours of fasting, you have a lot of people wanting to do that. I don't think from our population data, it doesn't look like you need to fast for 16 hours to get a benefit. And it just seems like that's kind of a torture. I just don't know that that's necessary. You know, what works isn't necessarily what is required? Yeah. There are even there was one study, looking at an 18 hour fast. So there's some pretty long, fasts. And again, I think of it as a lifestyle. So I don't know that I could do a 18 hour fast forever, you know?


Josh

yeah, exactly.


Dorothy

And so I think individuals should think about what works for them and their lifestyle and shoot for at least 12 hours of time where you're not putting any calories in into your mouth. And try to align your food intake with the daytime. Because that is when your body is ready to receive and properly handle those nutrients.


Josh

Yeah, absolutely. I think. Yeah, like you said, getting back into the cycle. Yeah. In the Western world it's 24 hours a day. Everything's Go go go.


Dorothy

Exactly.


Josh

Yeah. So trying to get back in touch with nature and the rhythms is super super important for people.


Dorothy

Yes. And I think also the light to you know, something to think about. It's something that we can control. So we can turn down lights in our room you know, in the living room when you're watching television, like I I often put my blue light blocking goggles on to watch television after 8pm on the computer if you're working on a computer, or your phone most devices you can turn off the blue light at night. It has a setting you can control your blue light and it really impacts when I get sleepy if I just put on those blue light blocking goggles and you know by nine o'clock I I'm ready.


Josh

Yeah, absolutely. Yeah, light is so important with that and blue light especially so yeah, not being on the computer right before you get into bed or your phone like you said switching it to night mode. I didn't really know that It had a night mode until quite recently. So i've been using that.


Dorothy

And sometimes I'll be working on the computer and it's eight o'clock and the computer start to change the colour like no. I can't belive i'm working that late.


Josh

Yeah. it reminds you doesn't it like you're still going you should be starting to relax Yeah. What are those blue light goggles you use What? Is that? Is that a specific brand or make?


Dorothy

The brand is Uvex u.v.e.x and I just found them on eBay. They look like safety goggles. And they're yellow.


Josh

Yeah. Yeah, that's cool I might have to get a pair of those.


Dorothy

And then you know, a lot of devices that we have have a little blue light, like you know, some light switches now have a little kind of


Josh

Like stand by mode kind of thing.


Dorothy

Exactly. So I also found online some little stickers so you can put the sticker over those little blue light things to really, really be careful that blue light influence because our bodies are really sensitive to the light. Yeah, and dim blue light in your bedroom particularly is detrimental for your sleep. It will suppress your melatonin secretion.


Josh

So yeah people with alarm clocks on the on the side table that's got a little blue light on it. That's affecting your melatonin release.


Dorothy

Yeah, exactly. And if you really like your alarm clock, they do have a kind of film so you can buy the film and then cut it and then paste it over your your light. Yeah, or get one with a red light.


Josh

Exactly. And I think Philips do like a whole light range, don't they? whereby you can adjust it or the time of the day like you said with your computer at a certain time it changes.


Dorothy

Absolutley Yeah, exactly. So I have a couple of lightbulbs in the house where it's these lamps that I use for my night lights and the plenty of light plenty of light but there's no blue light that comes out of that bulb. Those bulbs are not cheap. But they're l.e.d So last a long time but you can buy bulbs like that. And the ones like you said the change those are the really fancy ones. I think this is when we think about the changes in modern you know we think about what is modern life gonna look like I think we're going to have automatically dimming light. And when I say dim it even doesn't have to be dimming it just can be elimination of the blue light because you can have bright light that looks white but it doesn't have any blue lights. So people are working on developing these types of lightbulbs as well. So I think that you know and maybe put a lock on the refrigerator that turns on at eight o'clock.


Josh

I guess it when everything goes smart. You won't be able to open your fridge past eight o'clock or something like that.


Dorothy

Even things like blinds that automatically rise in the morning time. Would be really amazing. My husband likes to sleep with the curtains tight and black. And the problem is that then I I don't want to wake up.


Josh

Yeah, you'll just stay asleep


Dorothy

I'm very sensitive to the light. So I like sleeping with the windows open. And then when the sun rises. I can see that.


Josh

Yeah, okay. Yeah, exactly. And then you get that? What is that Melanopsin? Is that the one that comes in? the opposite melatonin basically.


Dorothy

Oh, yeah. Yeah,


Josh

Yeah, that kicks in and you're ready to go getting out. Getting out in that blue light early in the morning is really important.


Dorothy

I also try to do that as well. So in the morning, I like to go sit outside, you know, check my email, have my coffee and just be outside so that my brain is recognising. Okay? It's, it's the day time now. And studies show that if you have that bright light exposure during the day, it doesn't have to be a lot just like 15 minutes even that that makes you more resistant to the blue light at night. Because your brain is already knows like this is morning. So when when you have a little blue bit of blue light in the in the evening, after a morning like that, your brain doesn't get confused, because it had such a strong and training signal from the morning. Yeah, people who get that outdoor time. You know, even on a cloudy day, the light outside is much brighter than any bulb we can have on the inside. So just having that will help you to be more resistant to any blue light that happens to be in your environment at night.


Josh

Yeah, and just help you regulate, and like you said, get that clock started properly. Which is another thing in society, obviously, people living in apartments that aren't well lit or not enough windows and things like that.


Dorothy

Yes. Yes. You know, and it's very interesting, you know, again, coming back to like social issues like how do we help people learn about getting outside? What if they're in a place that's not safe to be outside or it's or it's too cold to be outside? Or you know, I live a lot in Phoenix, so it's too hot to be outside, you would think that in Phoenix, we'd all get a lot of sun. But you know, in the summertime, nobody does because everybody's inside it's just communicating that to folks that if it can't be outside, just sit next to a bright window if you can. You know you think about architects what are the window designs of the future that will help get more light in.


Josh

Yeah, yeah, there's so many areas of innovation to happen and it's good that people are people are starting to think about that and starting to work on that.