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 http://t.co/ABOAeQg5

Short link for this post Overnight Fasting a Key?   http://wp.me/p2jTRh-7d

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