Chronobiology – How Circadian Rhythms Can Control Your Health and Weight


“Chronobiology – How Circadian Rhythms
Can Control Your Health and Weight” The 2017 Nobel Prize in Medicine
was awarded for elucidating the molecular mechanisms
of our internal circadian clock. For billions of years, life on Earth
evolved on a 24-hour cycle of light and dark, and
so it’s no surprise our bodies are finely
tuned to that pattern. But put people in total darkness
without any external time cues, and our body still continues to cycle
in about a 24-hour circadian rhythm. In fact, you can even take
tissue biopsies from people and show the cells continue to cycle
outside the body in a petri dish. Nearly every tissue and organ in
our body has its own internal clock. An intricate system of intrinsic
clocks drives not only some of our behavioral patterns, such as eating,
fasting, sleeping, and wakefulness, but our internal physiology—our
body temperature, blood pressure, hormone production, digestion,
and immune activity. Most of the genes in our body exhibit
daily fluctuations in expression, making the circadian rhythm the largest
known regulatory system in the body. This cycle is thought to allow
for a level of predictability and functional division of labor
so that each of our body processes can run at the best time. At night while we’re
sleeping, a whole array of internal housekeeping activities
can be switched on, for example, and as dawn approaches our body
can shift back into activity mode. Anyone who’s ever had jet lag
knows what throwing our cycle even just a few hours off can do, but
now we know our circadian rhythms can literally be the difference
between life and death. A study of more than 14,000
self-poisonings found that those who tried committing suicide in the
morning were more than twice as likely to die than those who ingested
the same dose in the evening. In the same vein, properly timed
chemotherapy can not only end up being five times less toxic but also
twice as effective against cancer. The same drugs, at the same dose, but different effects depending
on the time that they’re given. Our body absorbs, distributes,
metabolizes, and eliminates what we ingest differently depending
on when it is during the 24-hour cycle. We’re just beginning to figure out the
optimal timing for different medications. Randomize people suffering
from hypertension into taking their blood pressure pills at bedtime
instead of in the morning, and not only does the bedtime group
achieve better blood pressure control and suffer fewer heart
attacks and strokes, but cuts their risk
of death in half. Yet most physicians and pharmacists tell patients to
take them in the morning, potentially doubling
their risk of death. If chronotherapy—the optimal timing
of drugs—can have such an impact, maybe it should come as no surprise
that chronoprevention—the scheduling of lifestyle interventions like mealtimes—
can also make a difference. In the official Academy of Nutrition
and Dietetics position paper on effective treatments for obesity,
importance is placed not only on the quantity but timing
of calorie intake, suggesting that consuming more
calories earlier in the day, rather than later in the day can
assist with weight management. Some have gone further and
even characterized obesity as a chronobiological disease. What evidence do we have to
back up these kinds of claims? Well, the timing of calorie intake
may have shifted slightly over the last few decades
towards a greater proportion of food later in the day,
which raised the question about a possible role
in the rise of obesity. Middle-aged men and women who
eat a greater share of daily calories in the morning do seem to gain less
weight over time, and a study entitled “Timing of food intake predicts weight
loss effectiveness” found that dieters eating their main meal earlier in the day
seemed to steadily lose more weight than those eating their main meal later. The obvious explanation for
these findings would just be that those who eat later
also tend to eat more. And there does seem to be a relationship
between when people eat most of their calorie intake and how many calories
they end up eating over the entire day, with those eating a greater proportion
in the morning eating less overall. Maybe later eaters are just
overeating junk on the couch watching primetime TV? A tendency has been found for night owls to eat
more fast food, soda, fewer fruits and vegetables. In the field of social psychology
there’s a controversial concept called “ego depletion,” where self-control
is viewed as a limited resource like a muscle that can become
fatigued from overuse. As the day wears on, the ability
to resist unhealthy food choices may decline, leaving one
vulnerable to temptation. So, is it just a matter of later
eating leading to greater eating? Remember this study where earlier
eaters steadily lost more weight? To their surprise, the early eaters were
eating as much as the late eaters despite the difference in
weight loss magnitude. The early eaters ended up about five
pounds lighter than the late eaters by the end of the 20-week study, even though they were apparently
eating the same amount of food. There didn’t seem to be any difference in physical activity between
the two groups either. Could it be that just the timing
itself of calorie intake matters? Scientists decided to put it to
the test, which we’ll cover next.

53 thoughts on “Chronobiology – How Circadian Rhythms Can Control Your Health and Weight

  1. Hello! New subscriber and youtuber here from Philippines. Lots of learning from this video.

    Click here my profile to visit my videos. Thank you.

  2. As a former substance abuser it had occured to me that starting with a substance early in the morning has the biggest effect, so I totally believe these theories.

  3. But wait, I'm pretty sure I saw a YouTube video that "proves" we came from outer space and we were sent to earth by our ancient forebears. I think it was by the Mormons.

  4. I hate to say it, Dr. Gregor, but having a person onscreen along with the papers is really distracting. I much prefer the old format. Regardless, keep up the excellent work!

  5. I'm going to reiterate my rule of thumb here, as Dr. Gregor provided the evidence to back it up: eat for what you're doing in the next ~4 hours. Going to work? Going to work out? Eat big. Going to sleep? Eat small.

    The hardest part, in my experience, is eating a small dinner at a restaurant while everyone else at the table is piling on.

  6. Wasn’t that chemo data wild? Amazing! And if you are on blood pressure medications, please share this video with your physician to ask to see if your timing is optimized.

  7. amazing… so interesting… Also, personally, I LOVE the new format… I like it much better than the old one, feels more personal and you are not distracting at all Dr Greger… You are animated and alive, just like you need to be… ♥

  8. How does this all tie in with intermittent fasting? Am I waisting my time if my food window is in the evening, ie fast all day and have my first meal at 5pm and last meal at 9pm? The reason for late eating is down to work and when the family is all together.

  9. Got to stop leaving us hanging, brah. Gets me anxious, then I keep voting with my dollar for my pharamceuticals!

  10. 02:00 A study about self-poisoning ? Is it just me wondering why so many people ingested poisonous seeds and by which coincidence there were scientists to keep track of all study parameters ?

  11. Super interesting, looking forward to the next segment…THX…….!
    Whole plant based foods on Instagram == mikewakethefoodup

  12. Ego depletion, THAT'S WHAT'S WRONG WITH ME! Now that I have a name for it maybe I can control it, at least a little bit…

  13. Wonderful presentation as always. I will respectfully say that having you on screen and all the studies popping up did become a bit distracting and I personally am able to absorb more info when you simply do a voice over while highlighting all the great information. Perhaps doing intros and outros where you are actively on screen and then cutting away to the old format in between? Just a thought. So grateful for this channel either way of course and I learned allot today. I just kept looking at you and then trying to read but then you again before finish reading because you are quite charismatic lol.

  14. Dr. Greger have you seen the information on the duckweed B12 plant source yet ?,,,hopefully looking forward to a video on the subject.

  15. Please go back to the old format of just showing the papers. Dr. Greger is sexy of course but its harder to just focus on the facts when they are harder to see than before and putting Dr. G in most of the frame does not add anything to the video. Please consider.

  16. Been following about half of Dr. Greger’s diet hacks from his book How Not to Diet, and I have lost 7lbs since Xmas. I just included the black cumin, ACV and green tea, and I have managed to not eat past 7pm about 40% of the time (giving up 30+ years of habitual night eating is harder than giving up meat!). 55 pounds left to go.

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