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What Is Metabolic Flexibility, and Why Is It Important? J. Stanton's AHS 2013 Presentation, Including Slides
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February 13, 2014
5:19 pm
v
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i am carrying my part of this conversation over to paul himself. a doctor also commented and wanted specifics so he could better help his patients. i'll be waiting hopefully for something i can actually use.

February 18, 2014
1:39 am
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ChrisM:

You're not the only person to give that feedback, so I'm sure my 2012 presentation will get a similar treatment.

 

tam:

That's beyond the scope of a comment: Petro digs into it in this very technical article

 

v:

I think part of the problem is that, unlike (apparently) the rest of the Internet, I don't feel comfortable giving medical advice to diabetics.

I've been assuming, perhaps wrongly, that anyone with a major medical diagnosis -- whether that be diabetes, anaphylaxis-level allergies, lupus, or anything else -- would need to filter any of my recommendations for general health through the needs of their specific condition, let alone any second-hand recommendations from sources I've found valuable for myself. 

If you feel misled by that, I apologize.

Yes, anyone with a known disorder of glucose metabolism should trust their glucometer over anything anyone else says.  I have long-term diabetic relatives who were first diagnosed decades ago and given advice even worse than what diabetics get now.  The reason they're still healthy is because they decided to trust the glucometer over the books full of terrible advice like "beans are great for diabetics."

Anyway, I'll be interested to hear what Paul says.  If I recall correctly, he does say that the "stock" PHD is not a diabetic diet, and that they will need to modify it appropriately to their needs.

JS

February 20, 2014
7:19 am
Dave
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Excellent article! I had to read it a couple of times to fully digest it.

February 21, 2014
1:34 pm
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Dave:

Thank you!  I prefer to give my readers a meal of solid, information-dense meat -- not a fluffy, sugary, low-information snack that leaves you hungry for real knowledge. (e.g. listicles) 

And yes, it takes longer to digest the meat.

JS

February 22, 2014
4:14 pm
tam
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February 23, 2014
12:09 pm
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Very interesting article and information, thank you again! A couple of questions, if you have a moment:

 

1-What types, frequencies, or intensities of exercises are most likely to restore and/or improve metabolic flexibility?

 

2-How might pre- or post-exercise feeding interact with the effects of exercise on metabolic flexibility? Are there eating strategies, e.g. re-fueling with carbs after a HIIT workout, that might be improving or diminishing the effects of the exercise on metabolic flexibility? Is there any value or harm in exercising in a fasted state?

 

Thanks!

February 23, 2014
3:00 pm
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The Pooch:

Those are excellent questions, which I've spent a lot of time on since I wrote and gave this presentation, and I'll probably write a full article on the subject someday.

Working on the principle that you train in the energy system you're trying to improve, it seems like a combination of two types of exercise would work:

1. Maximal fat oxidation usually occurs somewhere around and between 50-70% VO2Max, depending on how trained you are.  You can go a bit higher and you just end up burning carbs along with the fat, but once you get too close to VO2Max fat burning actually decreases.

Therefore, anything that elevates your heart rate via doing work for an extended period of time should help increase your fat-burning efficiency.  This includes all the variants of "cardio", but it also includes farmer's walks, high-rep kettlebells, barbells, or dumbbells -- and most importantly, playing around, whether via organized sports, solo sports, or (even better) unorganized play like climbing trees.

2. Resistance training (which means "weight training" for most of us) increases muscle mass, which improves our ability to dispose of both glucose and fat at all levels of mitochondrial efficiency. 

 

As far as fasted vs. fed training, that gets into mitochondrial biodynamics. 

1. Fed training will help increase your mitochondrial mass and population. 

2. Fasted training will increase autophagy, which culls the most broken of your mitochondria.  For maximum autophagy, train fasted and then don't eat for a few hours afterward, or as long as you can stand it.

There is a place for both: you can't train and recover fasted too much or you'll never gain any mass, but I believe it's good to do so occasionally in order to "take out the trash", so to speak.  It's an iterative cycle: by repeatedly culling the worst and causing the rest to reproduce, you should be able to build up a population of the best, most efficient mitochondria you have left, thereby maintaining the best health possible for you.

JS

February 24, 2014
6:31 pm
v
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still caught in the spam filter i guess :{

February 24, 2014
6:32 pm
v
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no i not! 🙂

February 27, 2014
8:59 pm
v
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test

March 6, 2014
7:07 pm
Amy B.
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J., this is absolutely *fantastic.* Thanks for putting it all together so cohesively and coherently. I *love* the notion of metabolic flexibility. As a (long time ago) former "cardio queen," back in the day, exercise was--as it still is for the uninformed--simply about "burning calories." After joining the lower-carb world and learning about fuel partitioning, and also about nutrient timing, a la Dr. John Berardi's Precision Nutrition's emphasis on proper post-workout nutrition & recovery meals, exercise became less about the calories and more about "giving glucose somewhere to go." I think that idea still has some merit, but over the past couple of years, I've learned more about what you've presented here -- and maybe the reason the "giving glucose somewhere to go" idea is at least somewhat accurate is *because* of metabolic/mitochondrial flexibility (including glycogen stores being flux, as they probably were to some extent throughout evolutionary history). I suspect there are plenty of people out there who've never really depleted their glycogen and have no idea what it's like to *not* have a full tank that keeps gets getting topped off...again and again. (High-sugar breakfast at 7, fat-free muffin at 10, pasta lunch at 1, cookies or pretzels at 3, you know the drill.)

As someone who spent years and years doing "all the right things" (tons of exercise, low-fat diet), yet remained chubby and inflamed, I truly love learning the biochem behind all this, because it's given me a new appreciation for exercise. The idea of exercise as a penance to be done for the "sin" of eating something nutritionally obscene is completely gone. (Thank goodness! What a terrible reason to want to get one's body moving, right?!) I see physical movement from a completely different perspective now.

I still go to the gym for a hard workout a few times a week, but I also do a ton of long, slow walks outdoors (even in the cold, I'll just bundle up) and some low-level lifting with weights at home. I can honestly say it's all a pleasure now. Instead of a punishment like it was so long ago, working out is an opportunity to keep myself healthy and fit for the long-term. I think lots of walking and other low-level activity is completely appropriate in an ancestral health paradigm, and I love how throwing in the occasional sprint session or bout of heavy lifting gives the mitochondria a reason, or a stimulus, if you will, to *remain* flexible. It's almost like "use it or lose it." If the metabolism has no reason to adapt to fat, or ketones, or carbs, or *whichever* of those is available at a given time, then it won't.

Being flexible and able to comfortably go many, many hours without eating, I have to suppress a chuckle (or maybe a pitiful head shake) when I overhear my coworkers talking about needing sugar at about 3pm...

And I've always wondered about hypoglycemics. To me, they are some of the most metabolically *in*flexible of all. If the blood glucose is going to dangerously low levels, that's a sign that whatever mechanism is supposed to bring it back up and keep things on an even keel is failing--be it cortisol, glucagon, epinephrine, etc. Either that, or obviously they haven't built up the ability to switch easily over to fat. Really fascinating stuff. (And of course, "dangerously low" means different things to different people. I can be in the mid to high 60s and feel fine, but someone who's accustomed to constant carbohydrate feedings throughout the day could be bonking in the low 80s.)

You are so very onto something here. Metabolic flexibility is likely at the heart of so much more than obesity. Are you familiar with Carl Lanore and his Superhuman Radio show? He likes to say, "Muscle is metabolic currency, so go to the gym and make a deposit today." Spot on, except it seems we can make those deposits in a lot of different ways. Heavy lifting once in a while is indispensable, but probably just movement in general, along with occasional fasting -- keeping our bodies doing what they were designed to do -- works flexibility wonders.

March 8, 2014
3:44 am
eddie watts
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use it or lose it: a saying that keeps its meaning, but can now be applied to so much more than it was originally intended.

it applies to everything in the body i think, if you don't exercise your mind through learning new things then the ability to actually learn becomes inhibited.
i think this is why older people struggle with learning new things when compared to younger people.

consider the learning curve of life in general: we learn so much from 0-20 years of age
then we mostly learn work and hobby related stuff moving forwards, as a consequence of getting older there is simply less available to learn *about* unless you make a conscious effort to find it.

is it really any wonder that a 60 year old finds it harder to learn new things?
chances are they have not learned new things for what? 20 years?!

(obviously not ALL older people, some will learn absolutely fine)
on the other side of things do any kind of general knowledge quiz and it seems to favour older people: even in groups where the age range is only 20-45 those falling into 35-40 and 40-45 just know so much more than those in the younger 20-25 group (in my personal experience)

i mostly fell across this idea because a paper in the UK ran a story along the lines of "old people struggle to learn new things because their brains are already so full of other information"
which just seems ridiculous to me!

March 9, 2014
3:32 am
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Further to this, consider how we've set up our environment and society so that we can simply glide through - pavements are smooth, roads are flat, automatic cars, desensitising footwear and so on.

My point being, get off the man-made and into the country - walking in the wild is so stimulating, eyes constantly scanning the way ahead, more minimalist footwear feeding back constantly. No wonder we feel so good, not only have we had a deserving break from the urban, but we've given our brains a new constant stimulation through nervous feedback.

Our brains do so much more than learn.

Living in the Ice Age
http://livingintheiceage.pjgh.co.uk

March 9, 2014
2:43 pm
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Amy:

"maybe the reason the "giving glucose somewhere to go" idea is at least somewhat accurate is *because* of metabolic/mitochondrial flexibility"

"Giving glucose somewhere to go" is only one part of it.  Exercise allows glucose to be transported into muscle tissues independent of pre-existing insulin resistance, post-exercise, which indeed helps dispose of glucose.  But met flex towards fat is an independent issue, which is mitochondrially mediated and improves over time as we exercise consistently: the mitos that reproduce tend to be those that are in the best shape, e.g. spewing less ROS.

I am convinced this is what's behind the need to keep snacking every few hours: blood tests show that you're not actually hypoglycemic (the common refrain from the medical profession "Reactive hypo is a myth"), but if you have trouble using fat for energy, you're going to feel crummy and need a sugar hit to keep going, regardless of whether your blood glucose has dropped or not.

And I strongly agree that leaving behind the concept of "I must burn X calories" frees us to do what we enjoy instead of grinding away on a treadmill/Stairmaster/bicycle that goes nowhere.  There are many mental benefits to being outside and physically moving around, in addition to the physical benefits of activity -- benefits lost by moving in place on a machine. 

"If the metabolism has no reason to adapt to fat, or ketones, or carbs, or *whichever* of those is available at a given time, then it won't." --> Yes.  Train in the energy system you want to improve.  PCr, glycolytic, aerobic glucose, aerobic fat...

And I've met Carl, but I've never been on his show.  Perhaps that should change.

Thank you for the note of appreciation!  Once you really "get" met flex, the light goes on -- and so many real-world phenomena that were once dark become illuminated.

 

eddie:

I agree completely.  I have to make a conscious effort to continue learning, because there is no encouragement to do so as you get older, particularly in today's emotion-driven consumer society.  Don't think!  Don't make rational decisions!  Let the beautiful flashing images on the TV screen determine your wants...and go consume them. 

People who make rational decisions don't make the economy grow in the absence of actual productivity (long since outsourced to Asia).  For that you need a population willing to take on debt.

JS

March 9, 2014
6:53 pm
tam
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Where can I get one of those RER tests? Maybe one day they'll sell it like breathalyzers.

March 10, 2014
7:57 am
Amy B.
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J -- you're right about hypoglycemia -- many people experience the symptoms while their BG is in the 80s -- well above any danger zone. And this really hammers home how very INflexible they are, that they need constant infusions of glucose because they don't have the metabolic machinery in place to switch to fat as needed. (Or if they do have the machinery, it's not working properly. Mitochondria asleep at the wheel after years of abuse.) I am so fascinated by all this. Proud to be a nerd! 😉

I've also heard that some people feel hypoglycemic not necessarily because their BG is "low," but because of how fast and how far it fell from where it *had been* previously. So they could be in the 80s or possibly even low 90s, but if it was much higher than that earlier and it fell rapidly, they get those hypo symptoms. Do you have any insight on that?

March 10, 2014
9:07 am
pam
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"You can’t exercise your way out of a bad diet." & vice versa.

i have noticed that runners around me often think they can "run off" a candy bar (or whatever

(maybe bicyclists too)

i think PHD (moderately low carb 10-30% + low protein) should work for most tho.

cheers,

March 10, 2014
10:59 pm
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Paul:

The irony in having made our lives so effort-free that we must "exercise" to remain healthy has not been lost on me.

Seriously: drive to the health club so I can ride a bicycle that goes nowhere?  As I said to Amy, there are many mental benefits to being outside and physically moving around, in addition to the physical benefits of activity.  Standing on a treadmill and watching TV isn't the same thing at all.

 

tam:

The equipment is usually found in exercise physiology labs.  It's generally used to measure athletic performance -- and I'm not aware of any MD who uses it as a health diagnostic.

 

Amy:

I've heard the same thing, that a rapid fall in BG produces hypos even though the absolute level is still "OK".  I'm still inclined to pin this on metabolic inflexibility, because as I note in the presentation, fat oxidation fails first.  You don't just randomly start having poor BG control (perhaps unless you're an incipient Type I diabetic)...the failure of fat oxidation is what appears to cause the poor BG control.  Petro at Hyperlipid has been going through the mechanisms for how this might be happening at the mitochondrial level.

 

pam:

It's interesting how everyone always gets hungry enough about 30-45 minutes after exercise to replace the calories they just burned!

Yes, the PHD is a good starting point for most people.  I tend to consume somewhat higher protein than it recommends, but I'm nowhere close to sedentary.

JS

March 17, 2014
3:55 am
Hal
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Thanks JS. Really interesting article.

One question - in those who can't oxidise fat to produce energy, where does all the fat go? Is it just wasted i.e. excreted? Or is it stored?

I ask because I suspect I might have a problem with this, although I'm not sure. I seem to only function with carbohydrates but I don't store fat - I'm very lean (skinny guy - 5'9 and 120lbs) - so I'm assuming it just leaves me.

March 21, 2014
12:14 am
pam
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i know a person who fuels before working out. then refuel after working out.

the shirt arrived. very cool.
(you should have "Die biting the throat" mug, pins, etc etc)

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