Dr. Satchin Panda's definition of ‘healthy’ — a circadian perspective
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A person's sense of their overall healthiness is influenced by many factors and changes throughout the day. A critical element in healthiness is the timing and content of our meals. Time-restricted eating, a form of daily fasting wherein the time of the day during which a person eats is limited, capitalizes on the body's natural circadian metabolic rhythms to promote health. In this clip, Dr. Satchin Panda describes his take on what "healthy" means from a circadian perspective and how time-restricted eating plays a part.
- Rhonda: Can you explain for people who just aren't very familiar with time-restricted eating or time-restricted feeding, as we call it with animal research, like, just what is that and how does that actually affect your metabolism of glucose and fatty acids and amino acids?
- Satchin: Yeah, so let's kind of step back and ask how does it relate to circadian rhythm, or the daily rhythms. So if we think of our daily health, our health, our personal sense of how we feel healthy changes from time to time throughout the day. So, for example, in the morning when we wake up, being healthy means you're feeling much rested and you're full of energy to start the new day. You're feeling actually much lighter, you should not feel that full stomach or grogginess, and have a good bowel movement. And then throughout the day being healthy means not feeling too hungry, so having some food in your system, and then being productive throughout the day. And then towards the end of the day being healthy actually means having taken a walk or something so you are not feeling really...you haven't moved all day and you're not feeling that sense of being constrained in a place. And at night time before going to bed being healthy means feeling really sleepy, so that as soon as we switch off the light and get into the bed we fall asleep. So in this way you can see that being healthy, this definition is very different at different times of the day. And a lot of it actually has to do with physiology or metabolism. So in the morning feeling lighter and not groggy and not having a food hangover means you have already gone through...hopefully somebody has gone through 10 to 12 or even 14 hours of fasting, not having food in the system, so that your body has metabolized all the food and has processed it and your gut has also gone through rest. And then towards the end of the day when you're going to hit the bed, if we have food in our system, what happens is blood flow is directed towards our stomach to digest the food and absorb it, so core body temperature remains high. So not having food for two to three hours before going to bed actually helps us to go have that deep sleep, sound sleep throughout the night. So in this way now if we back up and think, "Okay, so when should we eat?," then it makes sense that, well, after waking up maybe give one or two hours before we start eating, and then before going to bed at least three to four. Depending on what your metabolism, two to four hours before going to bed we should stop eating. So that brings up an eating window of, say, up to 10 to 12 hours max when we should be eating so that we have that personal sense of being healthy throughout the 24 hours. So in animal studies what we have done is we ask a very simple question. If we take animals and give them food just like most labs do, they have food in the hopper they can eat whenever they want, and we calculate how many calories they eat. And then we take another group of mice and then give them the same number of calories and from the same source of food, whether it's high carb, high fat, high fructose. It doesn't matter, we have to give the same source of food, same number of calories to the second group. And they have to eat all that food within 8, 9, 10, or even 12 hours. Then we consistently find that the mice that eat all their food within this 8 to 12 hours window are healthier than ad libitum fed mice. So that led to the term, what we call time-restricted feeding, where the timing of food when we eat is restricted or you define it and stick within it. Not caloric restriction, where you have to count calories and restrict it. So in this way it becomes very easier because you just have to...we all know how to manage our time, on a daily basis we are always dealing with time. So it becomes easier because if we start eating around, say, 8:00 in the morning and, based on our lifestyle, we can do 10 hours eating, then I'll have my dinner, say, around 6:00. So that's the concept of time-restricted eating or time-restricted feeding.
- Rhonda: And, yeah, I think that having the time where you just sort of say, "Well, I should stop eating by, you know, 6:00," or, you know, kind of having it so you don't have to constantly each day think about it, like, "When did I eat my first meal?," or," When did I take my first bite?" If you kind of just have this general schedule where it's, at least during the workweek, you know, it's easier.
- Satchin: And then another thing I must point out, that in our animal experiments, when we do these experiments, suppose we say eight hours, we've fed the animals for eight hours. And then every week we measure their food intake and some weeks they might eat less. And then we immediately change that schedule to, say, eight and a half hours or nine hours the next week to make sure that they actually eat the same number of calories. So moving this needle by one hour actually is not that detrimental. It still gives them the benefit. And we have also asked another question, so in animal experiments. In weekend we let them free, they can eat whenever they want. And they definitely go outside of a 12-hour window, they eat almost throughout the night. But still that two days of binge eating can be counteracted by if they stick to 8 to 9 or 10 hours during the weekdays. So that also gives us hope that perhaps in humans occasional eating maybe once or maybe maximum twice a week can still be tolerated.
- Rhonda: That's good to know, I guess a lot of people would be happy to hear that.
- Satchin: Yeah.
- Rhonda: What do you do? So for your typical workweek and then weekend schedule, like, what's your time eating window?
- Satchin: Yeah, so it's... You know, I travel a lot, too, but I...what I've found is if I stick to maximum 12 hours window, then I actually feel much better and more energetically, I sleep well, and I feel lighter, and I'm still productive throughout the day. So I start, say, somewhere around 7:00 or 8:00 in the morning, and then I stop around 5:00 or 6:00 in the evening. And I also try with different types of diet once in a while. One thing with many people who are new to time-restricted eating, or eating or feeding, is when they start it they feel hungry. And what we have found is while having a fiber-rich diet or a protein-rich diet or a slightly higher fat-rich diet actually helps to go through that longer time without food. And slowly you also get used to it. And all of these actually increase your nutrition quality because you're staying away from simple sugar and high glycemic food and you're leaning more towards food that takes a longer time to digest or longer time to absorb. So that helps. And that way my diet, both diet quality and also the duration have changed. And I usually stick to 12 hours, and in many cases I kind of try to stick to 10 hours.
- Rhonda: Oh, me, too. I try to stick to 10.
Latin for "at one's pleasure" or "as you desire." In biology, this term is used to describe "free feeding."
The practice of long-term restriction of dietary intake, typically characterized by a 20 to 50 percent reduction in energy intake below habitual levels. Caloric restriction has been shown to extend lifespan and delay the onset of age-related chronic diseases in a variety of species, including rats, mice, fish, flies, worms, and yeast.
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.
A molecule composed of carboxylic acid with a long hydrocarbon chain that is either saturated or unsaturated. Fatty acids are important components of cell membranes and are key sources of fuel because they yield large quantities of ATP when metabolized. Most cells can use either glucose or fatty acids for this purpose.
A value (between 0 and 100) assigned to a defined amount of a carbohydrate-containing food based on how much the food increases a person’s blood glucose level within two hours of eating, compared to eating an equivalent amount of pure glucose. Glucose has a glycemic index value of 100. Whereas eating high glycemic index foods induces a sharp increase in blood glucose levels that declines rapidly, eating low glycemic index foods generally results in a lower blood glucose concentration that declines gradually.
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.
Restricting the timing of food intake to certain hours of the day (typically within an 8- to 12-hour time window that begins with the first food or non-water drink) without an overt attempt to reduce caloric intake. TRE is a type of intermittent fasting. It may trigger some beneficial health effects, such as reduced fat mass, increased lean muscle mass, reduced inflammation, improved heart function with age, increased mitochondrial volume, ketone body production, improved repair processes, and aerobic endurance improvements. Some of these effects still need to be replicated in human trials.
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