Funny, I just listened to the second cholesterol podcast this morning .
The more I learn about biochemistry, the more I get distracted from systems thinking, the more I find I have to refocus on the latter.
My fasting experiment went terrible even though it was for a short period (2.5 days, though I originally intended 3.5 days). I’ve gotten LOTS of advice from everywhere on what to supplement and not supplement, etc.
But in thinking about it systemically it might simply be a matter of conditioning. Had I done 18 hour fasts for a while, then 24 hours for a while, then 48 hours, and so on – I’m confident my body would have better handled the 2.5 day fast better. Note the only difference in this case is that I was giving my body a better sense of anticipation through practice.
I know biochemically we can argue this pathway or that, but that’s the problem with this thinking, it distracts from consideration for a larger organic system that has different timespans of adaptation in it’s many overlapping processes.
I’ve heard autophagy is driven mainly by protein restriction. Insufficient dietary protein forces the body to more thoroughly scavenge and recycle protein. Eating fat while fasting to sustain BMR should have little impact on autophagy.
Interesting, I think some autophagy would help clean me up, seems like keeping protein minimal for a few days could do that without affecting metabolism.
28:44 Autophagy: mTOR is a major regulator of autophagy. Protein turns off autophagy. mTOR is a nutrient sensor, sensing protein. If your aim is autophagy, it is best not to use bone broth because it contains protein. In theory, you could eat pure fat and still achieve autophagy. With a classic water only fast, you may achieve autophagy in about 24 hours. Branch chain amino acids may negate autophagy as well.
Source - http://highintensityhealth.com/167-jason-fung-md-the-complete-guide-to-fasting-for-fat-loss/
Is this time frame from a ketogenic state or for a carb burner?
I really wish you would stop commenting about these supposed maximum fat oxidation rates. I
’ve hear you “explain” it several times but still have NO idea how you are coming to this conclusion. research regularily shows that average, deconditioned individuals can oxidize more than 10 mg of fat PER kg of bodyweight per minute (independant of bodyweight % of fat), indefinitely with light exercise in a fasted state. so a 100kg man can easily oxidize more than 60 grams of fat per hour, so one hour of exercise in a fasted state can be 540 calories (or KCal if you wish) easily.
a simple google search shows an almost infinite array of studies that demolish your “limits” on body fat oxidation, here is one for example
Dr. Fung made this statement regarding fat burners. He said carb burners would take a little longer since they have to deplete their glycogen stores before autophagy begins.
If your goal is to start a civil conversation about something you disagree with, it would be helpful to change the tone of your posts and eliminate the condescension and snarky double quotes. This isn’t Facebook or Reddit so the goal is not to “demolish” (quoting you, not snark) other people’s arguments or win the internet.
I haven’t seen any dogmatic tendencies in @richard and he’s already demonstrated the willingness to change his mind if he learns he was wrong about a particular topic. There’s no need come out swinging.
Have you given it another try? According to the calculation, I am only able to draw 187 calories per day from body fat. I’ve never tried fasting more than 14 hours myself.
This came up once on Facebook. I don’t recall if you participated in that conversation. As I explained then … that is the maximal rate of oxidation of lipids which is something entirely different from the maximal rate of release of lipids from adipose.
Right now, with a full belly, body fat is not your only source of energy. You have a steady stream of giant lipoproteins (chylomicrons) currying lipids from your gut throughout your body delivering their payloads to your cells, and they have been for several hours. Your liver is scooping up lipids from circulation, packaging them into low density lipoproteins and sending them throughout your body delivering their payloads to your cells. And of course if your insulin is low enough your body fat is releasing energy at the rate of 290 kJ/day for every kg of body fat. Your cells can also store energy in lipid droplets so they are not normally rate limited by adipose.
This explains how your cells can burn more energy when under load than your body fat can release for use.
BTW the actual maximal rate of lipid oxidation is apparently limited by the rate that we can transport lipids across our cell walls.
Prior to Jeff Volek’s FASTER study, it was generally accepted that the rate of maximal fat oxidation is predicted by VO2Max (aerobic fitness), Gender, and Exertion but not body fat - and is 1g/min with most athletes in the range of 0.45-0.75 g/min.
Jeff Volek was able to show that athletes who have become adapted to fueling on fat can oxidize energy at a rate previously thought impossible at 1.1 to 1.8 g/min. One key adaptation is an upregulation of the MCT transports, and a downregulation of glucose transports which could account for that.
The fact is however that these athletes were not fasted. They all had a high fat milkshake before getting on the treadmill and getting their needle biopsies.
If you fast for 10 hours, then you won’t have any lipids circulating in chylomicrons from your gut. Now if you fast longer and your energetic demand exceeds you adipose supply, you will draw down on lipids circulating in LDL, and at some point you will be rate limited by how much energy your adipose can deliver - which is a factor of your fat mass (minus insulin’s inhibitory effect if your fasted insulin is high), and roughly 31.5 kCal/lb Body Fat.
So if you have 20 lbs of body fat, you might think you have access to 3500 kcal x 20 = 70,000 and it is true that you do have 70k in your account but your daily ATM transaction limit is only 630 kCal/day.
I have followed all this as best I can although a lot of it is way over my head.
It seems like fasting is generally good for insulin regulation and autophagy, but you need to fast for long enough to get the benefits of the latter (24 hours + if fat adapted).
But, when fasting as a ketonian your body will first use up any circulating energy from recent meals and then only have body fat to drive energy from.
This energy is limited in the amount capable of released over any given time by the amount of fat on your body.
For people without too much excess fat in the first place they may find their bodies incapable of meeting their normal energy needs while fasting.
Does this mean that the fabulous energy release that I hear mentioned all the time in fasting talk just won’t happen for slimmer people who fast? Could their metabolism in fact slow down while fasting?
I only ask because I have slimmed down through a ketogenic way of eating to the top end of the “healthy” range, but still feel I have more to lose and had hoped to do an extended fast to try and get both benefits mentioned above.
Now I wonder if it is safe to do. What do you think Richard. I would appreciate your opinion.
I think you are following this very well. That is exactly how I think it works.
When you have enough body fat and you are fat adapted, fasting is easy.
When you don’t have enough body fat, your body will respond by reducing spending and looking for alternate sources of energy (ie: burning protein for energy instead of using it to make your body)
Congrats on your success. You might find that a fat supplemented fast doesn’t put you into an energy crisis.
Alright, as I understand anything that is hitting the stomach be it water, fat, whatever can cause an insulin response, even more so in those of us with a deranged metabolism. My question then becomes as we begin to fast after being Ketogenic for a while, in my case being full keto for over 7, almost 8 months, is fasting a good idea as if we are over producing insulin with anything we are ingesting, how would one be able to get into a fasted state sufficient to promote autophagy?
I can share my experience, @Bahrutile. I tend to be one of those who responds to anything put in the mouth. But, I found that a staged approach with extended fasting was very successful. Start with skipping one meal. And then 2 meals, with a short eating window. And then try skipping an entire day. That is followed by two days, and then three days…and then 1 week, then 2 weeks…etc.
Just remember that when you are not fasting, do not in any way restrict your meal (except for carbs of course). You absolutely must eat to satiety when not fasting, if you put yourself on an extended fasting regimen.
I’ve been able to fast both 48 and 72 hours, that was not the issue, i’m just curious that with a deranged metabolism even with a 72 hour fast are able to successfully cause autophagy as if even with water we may be secreting high levels of insulin.
I’ve noticed a huge turn around with my response to food with increasing stages of extended fasting. I don’t respond as much as I used to. For example, I could feel myself get cold and tired after eating. Even keto meals. This sensation no longer exists, which means I have stabilized my blood glucose levels. For me, the more extended fasting I do, the less insulinogenic dynamics in the future. And, more good news. I seem to lose weight faster during extended fasting. It’s like my body expects me to come out of it and feast on keto. Before, I would actually gain weight and hold on to weight during extended fasting. That’s how much my metabolic system was so screwed up!
As I understand it, fasting is one of the tools that can help reduce insulin resistance, so while initial fasts may not induce autophagy (or may only have minimal levels), as you address the IR, that should in theory improve.
No, I doubt I’ll be doing another fasting experiment anytime soon given the recent threshold discovery with my research. I’ll need to do a series of experiments to isolate and confirm/disprove the theory leading me to it.
I will say that my own personal experience does appears to echo @richard’s explaination in that I feel as though there’s this elasticity limit I’m hitting when fasting (even if just for 14 hours) that I wasn’t feeling when I had weighed more on keto while I was on my way down to the weight I am now. When I’m this low of weight and doing either a calorie restricted portion of an experiment or the fast, I feel puny and generally unhappy. And this in spite of seeing the highest ketone (BHB) levels I ever get >4.5.