Autophagy is more complex than you might think...and it’s another reason exercise is beneficial!


(Erin Macfarland ) #1

I find the host of this podcast a little annoying and he spends a lot of time trying to sell his programs but, there is some good info here regarding autophagy. Fasting is thought to be the most effective tool for inducing autophagy but exercise seems to be equally if not more-so. And it’s the most studied means of inducing autophagy and it’s related biomarkers. This is particularly of interest to those of us that are lean, athletic, and fat adapted. In the keto community fasting is venerated and almost implicit. But if you have low body fat, and are active, it can be challenging to fast for longer than 24 hours- and that duration isn’t really considered sufficient for inducing autophagy. But, the studies discussed in the podcast demonstrate that in trained, lean individuals that process starts relatively early, around 12 hours, especially when fasted exercise is being performed. And some fascinating info about tissue specificity, and that autophagy isn’t like a switch that is turned on and off in response to some particular biological conditions. Good stuff!

(Bob M) #2

I just listened to that this morning.

I’ve now listened to at least a handful of podcasts discussing autophagy, and I’ve gotten everything from binary (eat ONE CALORIE and autophagy stops) to something more nuanced, like the discussion linked above. It depends on length of time fasting, and also whether you are obese or not.

Could you find his links? I could not connect to get them, as I wanted to read the studies.

(Full Metal KETO AF) #3

Ridiculous, maybe for a few minutes max. That’s 1/4 gram of sugar, what about the glucose that’s always present in our blood even on an extended water fast?

#CalorieFascists :cowboy_hat_face:

(squirrel-kissing paper tamer) #4

This is good news for those of us who can’t fast. Thanks for sharing.

(Erin Macfarland ) #5

I haven’t looked for the links, but I’ll see if I can find them!

(Erin Macfarland ) #6

@PetaMarie I thought it was really helpful, it’s really hard to find information on who shouldn’t fast, or at least that not everyone needs to fast for extended periods. Glad you found it helpful!

(Central Florida Bob ) #7

This is encouraging. I’m not lean; I’m working on it but I think it has been 50 years since I was lean. I do 42-ish hour fasts three times/week and do an hour long bike ride around hour 38.

I’ll listen to this after today’s ride.

Thanks, Erin!

(Erin Macfarland ) #8

@CFLBob you’re welcome! When I started keto 5 years ago and inevitably came across Dr. Fung, there was pretty much no mention that longer fasts might be difficult or inappropriate for certain populations. All I heard was that anyone can fast for days on end- and it messed with my head because I couldn’t seem to get past a day and I thought something was wrong with me :joy: it wasn’t until a couple years into eating this way, and after the inception of the 2KD Facebook page, that Richard shared the formula for how much energy we can draw from body fat each day, and that it wasn’t “limitless” like popular opinion would have everyone believe. That’s when it clicked that there was a reason I started needing food right around the 20 hour mark. Because my body had literally run out of fat to burn. So I don’t feel so much like a loser anymore :grimacing:

(A fool and his bacon are soon parted) #9

Foortunately, the sales pitch is always at the beginning and is easily skipped. I, too, found Mike annoying at first, but he is going for an M.S. in biology (or something similar), so his science is sound. In some ways, he is actually an American version of Richard.

In the absence of dietary carbohydrate (or carbohydrate below one’s tolerance threshold), it is not a factor. The reason being that the milieu is one of high glucagon, so the insulin/glucagon ratio is low, thus promoting catabolism.

(Full Metal KETO AF) #10

@PaulL So are you saying that 1 calorie spoils autophagy? :cowboy_hat_face:

(Hyperbole- best thing in the universe!) #11

It makes sense to me that autophagy is not soley dependent on fasting. It is an important part of health mainenace and it is logical that lean and plump (fat or just bodies with sufficient but not excessive fat stores) would have different mechanisms for accomplishing the same goal.

If we can remember that it is out cultures (be it gymrat or couch potato) that are messed up and not our innate biology maybe it will help us listen better.

(Andi loves space, bacon and fasting. ) #12

Fung works almost exclusively with T2D and very obese people, I think he doesn’t realize that his videos and interviews are watched by all sorts of people looking to improve their health.

You are a bad ass!!

(Central Florida Bob ) #13

I have to admit that applying Richard’s formula messes me up somewhat. I have about 50 pounds of body fat to get rid of. Still, at 31 calories per pound per day, that’s about 1550 calories. According to my Renpho scale, my BMR is around 1850 calories (about the same as online calculators), and day to day life itself puts my requirements above that. These guys say about 2600 calories/day. Then add in 560 or so for my bike ride (using online calculators and not measuring the number of watts I put into the pedals) and it looks like I need 3100 or more calories on my fasted days and yet I should only be able to get 1550 out of fat. I need twice as much energy as I can get out of fat. Yet (1) I feel fine and (2) my weight loss is slow that I’m not sure if it’s actually happening.

I don’t understand. I suspect my rides become glycogen fueled, but I don’t know how those numbers work out. Glycogen has to come from somewhere and would have to be resupplied by gluconeogenesis from eating days.

Allow me to assure you that you’re the only person in history who has ever said that!

(bulkbiker) #14

Autophagy is still bleeding edge science…
Anyone who claims to have all the answers about what stops and starts it is talking complete and utter bull. Its still all 100% guesswork at the moment.


Yes, you’re using some glycogen - more at higher intensity levels (low cadence, high exertion) and you’re recycling lactate back into GNG also. Depending on where your baseline insulin sits you might be getting way more access to fat during exercise periods than what was accounted for in the study calculations.

What online calculator are you using for bike calories? In lieu of a power meter, I’ve found Strava to be a good approximation. They’re based on gps and elevation changes, and they incorporate data in their calculations from people riding the same route who do have power meters.

(Central Florida Bob ) #16

I went down the rabbit hole trying to remember where I got things. For day to day, I have some Excel data I ran long ago, and just have a printout of a few numbers. I don’t recall where I got the formulas.

I do have one site I’ve bookmarked and that’s

The tricky part here is that the authors have captured a lot in the choice of bikes. I find I can get correlation between the speed&power calculator and the spreadsheet but It takes some fooling around with the calculator, though.

I think the problem is that so many things affect the amount of calories you burn that it’s tough to fit into an easy calculation.

(Erin Macfarland ) #17

@PaulL yeah you can get through the advertising stuff, and he is a reputable source as far as his knowledge basis is concerned, I just get irritated by neurotic types which is kind of the vibe I get from his podcasts and videos, lol. Richard is super down to earth, I dig that!

(charlie3) #18

Common sense tells me autophagy is happening 24/7 but may be accelerates during fasting. It’s also common sense to me that being more active, burning more calories, would also tend to accelerate autophagy. Cell repair must be a necessity or we die.