What time to start eating when doing time-restricted eating | Satchin Panda

Posted on July 12th 2019 (over 5 years)

Parent Episode: Dr. Satchin Panda on Practical Implementation of Time-Restricted Eating & Shift Work Strategies

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Rhonda: Another sort of question that sort of relates to this is, and people ask this all the time, is what about people that are...start eating later in the day? For example they wake up 8:00 in the morning, but they don't eat until noon. So let's say they eat their first bite of food at noon, and they stop eating at 8:00 p.m. So that's an 8:00 TRE eating window. And they go to bed by 11:00 or so. Do they still have the same benefits or are they losing because it's like the time-restricted eating window has kind of shifted to later and obviously there is a light/darkness component to all this to some degree?
Satchin: Yeah, yeah. So those questions we haven't even teased them in animal models, but I'm sure some people will start teasing them apart. So what happens is in the morning we know insulin sensitivity is at its best. So people who have a bigger meal earlier in the day, they have less insulin spike, less glucose spike, etc. Having said that, we don't know for people who are starting their food every day at noon whether their best insulin sensitivity is at noon or it actually happens at 8:00 in the morning. So that information we don't know. So this is where some studies need human volunteers who are doing this. And maybe some people who are doing...who are starting to eat at noon, one day maybe they can drink a glass of juice at 8:00 and prick themselves and get a glucose reading and monitor themselves. And then another day, a week later at noon, they will eat the same glass of juice and prick themselves and see how is their glucose response. So that's a simple self-experimentation with some healthy people. If they're out there, then they can do that. And if they post it, that will be really nice. Second thing is what happens toward the end of the day at night. So this is where it becomes a little bit complicated because, as you said, there is day and night transition. And we know that in the evening as our body prepares to sleep, our melatonin level begins to rise. And that melatonin usually rises two to three hours before our habitual sleep time. So if somebody is going to bed around 11:00, then that melatonin is beginning to rise around 9:00. On an average, but some people it might rise around four hours earlier and some people it will rise exactly at bedtime. And when melatonin rises, there is new data showing that melatonin can bind to its receptor in the pancreas. And this engagement of melatonin with the pancreas receptor essentially tells the pancreas, "Okay, it's time to sleep, you don't have to bother releasing insulin." So in that way what happens if somebody is having a big meal when there's high melatonin, then there may not be enough insulin to release from the pancreas and glucose may stay high in the blood circulation for a long time. And this study...these kind of studies came to publication because almost 10 years ago large genome-wide association studies found that people with obesity or diabetes might have a mutation in melatonin receptor. And that was confusing because what has melatonin to do with obesity and diabetes? And you fast-forward 10 years, people went back to the drawing board and looked at where the receptor is expressed and what it does when melatonin is engaged, and then they found out that there is this effect of melatonin on insulin. So that's why people who are eating late into the night, they may not get the best benefit in terms of glucose control because their glucose might remain slightly higher than if they had the same dinner two hours earlier.
Rhonda: If they're making more melatonin.
Satchin: If they're making melatonin. So it's very...so that's why I said it's complicated.
Rhonda: Yeah.
Satchin: But at the same time I would say eating randomly over 12 hours, 15 hours, versus eating to this 8 hours, even though it starts at noon, I will prefer the 8 hours starting at noon.
Rhonda: Right. So it seems like there's, in addition to, you know, the timing of your food intake, so we know the first time you're eating sort of starts a lot of these liver enzymes and metabolism...glucose metabolism and all these things. In addition to that, that circadian rhythm being regulated by just the food intake, there's also this whole melatonin issue and the night-daylight cycle and, you know, when you're starting to make more melatonin. And all that complicates things, as well.
Satchin: Yeah.
Rhonda: It seems. Yeah, I remember a study that was done where I think men were given the same caloric meal in the morning and the evening.
Satchin: Yeah.
Rhonda: And glucose was measured and the blood glucose levels were much higher in the evening versus morning. But, of course, they could have been. Who knows how long... You know, was the morning, like, 8:00 a.m. , and then they were doing, you know, 9:00 p.m.or 8:00? So who knows what their timing window was, right?
Satchin: The habitual meal, what is their habitual meal?
Rhonda: Right.
Satchin: That's a very widely observed phenomenon. In fact, there was a term for that that was called evening diabetes. So a person might be healthy in the morning based on blood glucose. In the evening if you do the same postprandial glucose tolerance test and then look at the glucose level, then maybe diagnosed diabetic.
Rhonda: Right, right, yeah.
Satchin: Yeah.
Rhonda: Well, I think the other component to this would be the fasting component, right? So people think, "Well, I'm only eating within an eight-hour window, so I have a much longer fasting period." And I think that's maybe uncoupling some of these differences between time-restricted eating, being on a circadian rhythm, and fasting, intermittent fasting, prolonged fasting. You know, there's so many different terms out there.
Satchin: Yeah.
Rhonda: And I think sometimes a lot of it just all gets mushed together in one group and it's, like, all the same.
Satchin: Yeah.
Rhonda: But it's not actually all the same.
Satchin: No, it's not the same. So, for example, even not having food in your system for 12 to 16 hours, whether it's fasting or not, that's debatable. Because some people say, "Well, it's not fasting, it's not having food for 12 hours." And I think that's where I would say not having food for 12 to 16 hours is not fasting, but maybe giving rest to your system, rest and repair and rejuvenation of your system. So when we think about fasting, or when you think about fasting, two things come to mind. Feeling hungry. And feeling hungry has many different connotations, many different intensity. So one sense of feeling hungry is, well, you might feel light. And then second, your stomach may begin to frump a little bit. And then I always say that is your stomach is telling you, "Well, I'm repairing myself." You're not actually really hungry, you're not getting low energy that you cannot get up from the chair or run or something like that. And then after several, maybe one or two, days of fasting, or maybe after 24 hours of fasting, some people will get a head ache. So that's a good sign that, well, your brain is not getting enough energy in its habitual usual form and may be trying to signal the rest of the body that the body has to send some other form of energy, for example ketone bodies or something. So in that way fasting, if you're measuring fasting or you're defining fasting in terms of ketone body formation above a certain level, then that may kick in after 24 hours. Or if you have that threshold even much higher than fasting, maybe 20, 48, or 72, or even 96 hours before you see that level of ketone bodies that can be your definition of fasting. So in that way I think the way you define fasting will determine whether 24 hours, 48 hours, 96 hours, or even 12 hours or 16 hours is fasting. But the way we think, we kind of define how many hours your system should not have food is based on our daily circadian rhythm. Because if you think about what are the key elements to being healthy, it boils down to three important things. One is sleep, and the second one is nutritional food, and the third one is physical activity. And these three are interlinked with each other. So, for example, if somebody is sleep deprived or didn't have sleep, then it's very hard for that person to do physical activity the next day or go on a marathon. So these two are interlinked. Similarly, if somebody is eating for 15, 16 hours and has a very heavy meal at the end of the day, then it affects sleep. It also affects physical activity. One cannot run with a full stomach. So these three are interrelated. So on a daily basis what we feel is having...limiting food to 8 to 10, or maximum 12, hours helps to coordinate these three foundations of health to work on a daily basis and give us healthy benefit. So on a very simple sense if I want to relate time-restricted eating and then maybe long-term fasting, one day of fasting, two days of fasting, or four days of fasting, which definitely have much more benefit, then it's almost like taking care of your teeth. So brushing every day is like time-restricted eating. There's the minimum one can do and that's something necessary to take care of your teeth. But, again, once in a while, maybe twice a year or three times a year or once a year, depending on how much you want to take care of your teeth, you want to go see a dentist. So that's almost like a prolonged fast one has to do once a year. So similarly I do four to five days of water fasting only once a year and that absolves all the other sins with my feeding that I might have committed throughout the year. So in that way I think the difference between time-restricted eating and other forms of fasting is one can adopt time-restricted eating as a true lifestyle, starting even from teenage or even toddler years, all the way through when you are 80s, 90s, or even 100 years old. Whereas this long-term fasting, two days or four days of fasting, forget about even teenagers doing it. And some older people who are very fragile, they might not be able to do it. And you need medical intervention or some kind of supervision to do it. Many people who are slightly unhealthy, even some diabetics who might go hypoglycemic after 10, 12 hours, type 2 diabetic I mean, they may not be able to do it without medical supervision. So although those long-term fasting definitely have much benefit, and that has been shown in multiple studies, the need is that they can be practiced only by a certain type of people at certain days and need more mental resolve. And it may not be an everyday lifestyle, whereas time-restricted eating can be an everyday lifestyle.
Rhonda: That's a great way of putting it.

Circadian rhythms

The body’s 24-hour cycles of biological, hormonal, and behavioral patterns. Circadian rhythms modulate a wide array of physiological processes, including the body’s production of hormones that regulate sleep, hunger, metabolism, and others, ultimately influencing body weight, performance, and susceptibility to disease. As much as 80 percent of gene expression in mammals is under circadian control, including genes in the brain, liver, and muscle.^[1] Consequently, circadian rhythmicity may have profound implications for human healthspan.

^ Dkhissi-Benyahya, Ouria; Chang, Max; Mure, Ludovic S; Benegiamo, Giorgia; Panda, Satchidananda; Le, Hiep D., et al. (2018). Diurnal Transcriptome Atlas Of A Primate Across Major Neural And Peripheral Tissues Science 359, 6381.

Enzyme

Any of a group of complex proteins or conjugated proteins that are produced by living cells and act as catalyst in specific biochemical reactions.

Insulin

A peptide hormone secreted by the beta cells of the pancreatic islets cells. Insulin maintains normal blood glucose levels by facilitating the uptake of glucose into cells; regulating carbohydrate, lipid, and protein metabolism; and promoting cell division and growth. Insulin resistance, a characteristic of type 2 diabetes, is a condition in which normal insulin levels do not produce a biological response, which can lead to high blood glucose levels.

Intermittent fasting

A broad term that describes periods of voluntary abstention from food and (non-water) drinks, lasting several hours to days. Depending on the length of the fasting period and a variety of other factors, intermittent fasting may promote certain beneficial metabolic processes, such as the increased production of ketones due to the use of stored fat as an energy source. The phrase “intermittent fasting” may refer to any of the following:

Time-restricted eating
Alternate-day fasting
Periodic fasting (multi-day)

View fasting topic

Ketone bodies

Molecules (often simply called “ketones”) produced by the liver during the breakdown of fatty acids. Ketone production occurs during periods of low food intake (fasting), carbohydrate restrictive diets, starvation, or prolonged intense exercise. There are three types of ketone bodies: acetoacetate, beta-hydroxybutyrate, and acetone. Ketone bodies are readily used as energy by a diverse array of cell types, including neurons.

View beta-hydroxybutyrate topic

Melatonin

A hormone that regulates the sleep-wake cycle in mammals. Melatonin is produced in the pineal gland of the brain and is involved in the expression of more than 500 genes. The greatest influence on melatonin secretion is light: Generally, melatonin levels are low during the day and high during the night. Interestingly, melatonin levels are elevated in blind people, potentially contributing to their decreased cancer risk.^[1]

^ Feychting M; Osterlund B; Ahlbom A (1998). Reduced cancer incidence among the blind. Epidemiology 9, 5.

Metabolism

The thousands of biochemical processes that run all of the various cellular processes that produce energy. Since energy generation is so fundamental to all other processes, in some cases the word metabolism may refer more broadly to the sum of all chemical reactions in the cell.

Postprandial

Relating to the period after eating. Postprandial biomarkers are indicators of metabolic function. For example, postprandial hyperglycemia is an early sign of abnormal glucose homeostasis associated with type 2 diabetes and is markedly high in people with poorly controlled diabetes.

Prolonged fasting

A type of intermittent fasting that exceeds 48 hours. During prolonged periods of fasting, liver glycogen stores are fully depleted. To fuel the brain, the body relies on gluconeogenesis – a metabolic process that produces glucose from ketones, glycerol, and amino acids – to generate approximately 80 grams per day of glucose [1]. Depending on body weight and composition, humans can survive 30 or more days without any food. Prolonged fasting is commonly used in the clinical setting.

[1] Longo, Valter D., and Mark P. Mattson. "Fasting: molecular mechanisms and clinical applications." Cell metabolism 19.2 (2014): 181-192.

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