Circadian Rhythm


Two interesting interviews on CBC Radio regarding circadian rhythm.

The first is an interview with a researcher about a study linking risk of breast cancer with years of working graveyard shifts.  This is followed by another interview regarding circadian rhythm in general.

Interview on CBC

The Precious – Sleep Denial and What We Throw Under the Bus

This photo shows an owl perched at a tree bran...

This photo shows an owl perched at a tree branch at night. According to Brit, this is Barred Owl (Strix varia). (Photo credit: Wikipedia)

The rock we are battered against.

The public health hill hardest to take.

The “precious”, gripped ever tighter in our hands no matter the consequences.

We wants it, the “precious”.*

OK, what on earth could I be referring to?.  Well, pick your metaphor or I’m sure you could come up with a few of your own.  What I am referring to is:

Denial of the need for adequate sleep.

Denial of the need for circadian rhythm health.

We don’t like being accountable. I sure don’t. It’s so boring and frustrating.  Aren’t we born to be free?  As a society, we’ve had to learn the hard lessons about money.  Now we are having to learn the hard lessons about food choices and weight health (and no, I don’t mean the simple calories-in-calories-out stuff).  Barely visible yet on the public radar are the hard lessons we will face about chronic under-sleeping and chronic circadian rhythm disruption.

When it comes to weight health, think of all the blogs and comments and tweets out there. I have seen countless posts and comments from people willing to turn their whole eating pattern on its head. (I have.) Willing to learn and chase the smallest details. (I have.)  Willing to spend hour upon hour tracking various people’s opinions and the latest commentary, insights and research. (I do.) Many put time and effort into being more active or engaging in a deliberate exercise program.  People talk about which medications might interfere with weight health.  Some pursue unusual techniques that are like grasping at straws. There are countless ways people take measures aimed at improving their ability to have and hold their chosen target weight.  Many times a lot of time, effort and loss of personal freedom is involved.

In all this, how often is a goal of adequate sleep and normalised circadian patterns targeted or achieved?

How much of all the other stuff we are doing is only necessary because of the chronic sleep/circadian issues?

In other words, what are we throwing under the bus in our attachment (sometimes fierce attachment) to keeping short sleeping hours and eating/sleeping/waking in disordered, non-rhythmic patterns?  One type of cost is the health impact from the sleep/circadian issues themselves.  This is a huge field of study and I won’t try to review it here.  A number of studies have linked sleep deprivation and circadian disruption with a tendency to gain weight.  (You can see some of this under the category “Sleep Heals” in the sidebar.)

The second type of cost is what we do to try to cope with the effects of the sleep disruption – instead of sleeping!  Just as an example, what if most of your tendency to gain weight would resolve if you just got well into a program of regular adequate sleep and a regular circadian patterns of sleep and meal timing?  How much less burden might there be from all the total things you do now that are for the purpose of helping you control your weight?  For example, research suggests that you would likely have some improvement in your ability to handle carbohydrates.  Research also suggests you would likely have less of a desire for sweets or reward foods.

If you have been chronically low on sleep, the benefits of getting regular adequate sleep are not going to be clear in the first weeks. In fact, there is a confusing phenomenon whereby people who have really been driving themselves and then get a night or two of unlimited sleep can suddenly feel much worse as the adrenalin levels fall and the body pushes you towards going into a “repair and recovery” mode of increased sleep for a while. This is very often mis-interpreted. People take this phenomenon, which is really an expression of the body’s desperation for sleep, as an excuse justifying their high-adrenalin habits.

The heart of the matter is time. We want more time. I don’t know of any other topic in weight control that can make so many people respond as if they are personally under threat.  In terms of emotional response, this topic is even worse than that terrible and much dreaded horrific topic – breakfast.

Of course, the topic of breakfast and skimped/skipped meals ultimately also involves time and time pressures for many people. (See the page “Restrict/Rebound” under Key Keys above.)

So, what are you “throwing under the bus” instead of turning the computer off and getting to bed?  I’ll be asking myself the same question more often.

*Lord of The Rings

Overnight Fasting a Key?

From The Salk Institute comes an intriguing study relating to the timing of meals, snacking and the length of over-night fasting:

Scientists have long assumed that the cause of diet-induced obesity in mice is nutritional; however, the Salk findings suggest that the spreading of caloric intake through the day may contribute, as well, by perturbing metabolic pathways governed by the circadian clock and nutrient sensors.

The Salk study found the body stores fat while eating and starts to burn fat and breakdown cholesterol into beneficial bile acids only after a few hours of fasting. When eating frequently, the body continues to make and store fat, ballooning fat cells and liver cells, which can result in liver damage. Under such conditions the liver also continues to make glucose, which raises blood sugar levels. Time-restricted feeding, on the other hand, reduces production of free fat, glucose and cholesterol and makes better use of them. It cuts down fat storage and turns on fat burning mechanisms when the animals undergo daily fasting, thereby keeping the liver cells healthy and reducing overall body fat.

The daily feeding-fasting cycle activates liver enzymes that breakdown cholesterol into bile acids, spurring the metabolism of brown fat – a type of “good fat” in our body that converts extra calories to heat. Thus the body literally burns fat during fasting. The liver also shuts down glucose production for several hours, which helps lower blood glucose. The extra glucose that would have ended up in the blood – high blood sugar is a hallmark of diabetes – is instead used to build molecules that repair damaged cells and make new DNA. This helps prevent chronic inflammation, which has been implicated in the development of a number of diseases, including heart disease, cancer, stroke and Alzheimer’s. Under the time-restricted feeding schedule studied by Panda’s lab, such low-grade inflammation was also reduced.

“Implicit in our findings,” says Panda, “is that the control of energy metabolism is a finely-tuned process that involves an intricate network of signaling and genetic pathways, including nutrient sensing mechanisms and the circadian system. Time-restricted feeding acts on these interwoven networks and moves their state toward that of a normal feeding rhythm.”

The way this study has been presented in some media could be mis-leading. Have a look at the above link to understand what the study did and what it found.  The critical facts are that this was done in mice (human implications can only be guessed at), rodents respond to intermittent fasting much differently than humans do, mice normally eat at night and sleep in the day (which can get a little confusing as you read about the study) and they were fed a 60% fat diet, which probably means about 20% or more of carbs.  Any time a diet is studied that has a mix of fat with this much or more carbs, the results cannot be taken as showing what the results would have been with low-carb eating.

Still, I think this is a very important study.  It is also one that, BTW, contributes to the a-calorie-is-a-calorie food fight (but that is not likely to be acknowledged). This study does not actually demonstrate that these factors apply to humans, but it is certainly possible, at least even to some degree.

IF humans actually respond similarly to the way the mice responded in this study, what would that mean?  I think it is worth addressing that question, keeping in mind that this is just theory so far.

(1) It would suggest that it is generally best to have a relatively longer time between your last food of the evening and your first food the next day.  For example, having your dinner as early in the evening as works for you (that is, without setting up a situation where you are repeatedly or persistently hungry) and then avoiding snacking in the evening or night.

None of this at all changes my opinions and concerns expressed on the page “Restrict/Rebound” or in my writings about “Satiety-Focused Weight Health“.  So, from my perspective, this would mean working with your body to establish daily eating habits and routines that allow you to meet these goals without putting up with ongoing hunger.  Of course, sometimes when you are changing your eating patterns or metabolism there may be some extra hunger for a few days or a week or so as your body adjusts.  For example, if you are in the habit of getting up in the night to eat, it may be a useful strategy to just stop this and tough it out for a few nights while your body adapts (unless, of course you have a specific medical need, such as being a diabetic who can have hypoglycemia overnight).

Many people who adopt a low-carb or at least a controlled-carb lifestyle find that they are much less interested in snacking.  This is probably for different reasons for different people, due to the various ways that eating low-carb promotes satiety.

(2) Even further, it might suggest that it is best to avoid having food still in the early part of the digestive process as you go into the later evening (when your digestive system would be starting to slow down) and on going to bed (your digestive system slows overnight).  This would be influenced by the timing of your evening meal relative to your circadian rhythm, the mix and amount of food eaten and also the functioning of your digestive system.

I could imagine a perfect storm for this would be a diabetic, who has delayed stomach emptying from nerve damage, on a medication that slows stomach emptying eating a large meal containing fat (slows stomach emptying) and protein (slows stomach emptying) and lots of very slowly-digesting starchy food (e.g. legumes, “al dente” pasta) who eats from 8 pm to 9 pm and goes to bed at 11:30.  That person’s digestive system just isn’t going to get any rest.

(3) What about creating a longer fast by skipping or delaying breakfast?  Sorry, I’m still a “Nope, I don’t think so” on that one.  I’m not an anthropologist, but I think the wisdom of the ages in human culture has pointed to a regular intake of meals, including breakfast.  Young, metabolically healthy people can get away with it for a while, but I don’t think it’s a strategy that holds up as the decades start to pass or if you are metabolically unwell or you are under chronic stress.  (See Restrict/Rebound page and comments.)

(4) In the day, moving away from snacking may be beneficial (again, working with your appetite/satiety system on this).

On the subject of meal timing, as I recall other studies have shown that your digestive tract and your appetite/satiety system work best when you have a regular, predictable circadian pattern (wake, sleep and activity) and also when you have regular meals of a generally similar make-up.  That is, your body functions best when it can get into the habit of digesting, for example, a lunch eaten at about the same time each day and containing a similar amount of food and mix of types of food day to day.  Your body wants to anticipate a certain job it has to do with your breakfast, and a certain job it generally has to do at lunch time and also a certain general job you expect from it at supper time.

When I was growing up, we rarely ever snacked in the evening.  There was always tasty stuff in the fridge and always cookies or other baking on the counter.  We ate dinner at about 6 pm, had a small dessert and the simple fact was that none of us thought about food again until the morning.  On the other hand, none of us would be happy with being up long at all in the morning before eating breakfast and none of us would ever have been happy skipping lunch.

This study from the Salk Institute does not provide solid information about human biology, but still I would suspect that the human body functions best when the digestive tract and metabolism can rest at night.

Addendum: another take on the same study, from Sweat Science

Short link for this post Overnight Fasting a Key?