Ability to use fat as fuel for endurance sports

(Blyss (Old @Charmaine)) #38

@Becky_Bataller_Naugh it’s been very helpful to me and I love the podcast. You’re quite welcome!

(ianrobo) #39

anything Peter has to say if you are seriously interested in endurance sports must be listened to

(Genevieve Biggs) #40

I’ve been reading through an old forum exchange with The Bear, veteran and pioneer ketoer and Zero Carber. At the time of exchange he ate only meat (and eggs, etc.) for 47 years. He contends that the skeletal muscle does not use glucose or glycogen, but only fat. The reason runners hit a wall because they are carb loaders whose bodies are not used to running on fat longterm. Quote:

"Glycogen is not depleted by exercise, period. The muscles ONLY use free fatty acids complexed with n-acetylcarnitine to provide the energy to reverse ADP to ATP, no carbs are consumed in this process, either as glucose or as glycogen.

The famous ‘wall’ hit by runners etc., indicates a problem in mobilising bodyfat in a carb-loading individual once dietary circulating fat is consumed. It does not occur in a keto-adapted meat eater."

(ianrobo) #41

thats true because body is used to fat as energy not carbs but in that quote I am presuming he is not talking about the high periods of intense energy usage (HIIT, Zone 5 and above etc), in fact he is confirming the FASTER study that fat is used much further up the power/HR zones than used to be thought.

(Genevieve Biggs) #43

Just came across this:

#44

Nice summary of the FASTER study, which is linked at the end. Here’s a chart from it showing fat vs glucose utilization in high and low carb athletes:

Screenshot_2017-01-07-05-40-52-1.png720×1124 152 KB

(ianrobo) #45

I have just done a 4 hour 110KM fasted ride the quickest I have done over 100km and over 1kph quicker than same ride two months ago, This was also on VESPA so FASTER is not only proved but my N=1 proves it.

However anyone comes across the Endurance Planet podcast, listened to the last but one one on the ride and unbelievable. This podcast says it is about fat burning then says anyone eating under 50g of carbs are damaging themselves ! They think you can be fat adapted and still eat 100g of carbs a day. In fact their guest claimed Keto was damaging after the first 6 weeks and everyone’s performance dipped, course it does you are not fat adapted yet !

As I was riding I was screaming at this nonsense and for a podcast that I have enjoyed until now, I could not believe what I was listening to.

#46

I don’t think that the same rules apply under intense exercise. I’ve certainly found that my energy stores are far in excess of when those calculations allows for.

Theoretically (using those calcs), my fat stores allow for only ~500 calories of energy per day. Under exercise, I’ve easily burnt 4,000 cals. This should tap all my glycogen and fat daily reserve

Weirdly, under normal fasted conditions, I do feel pretty poorly if hit 1,000 cal deficit.

I don’t have any science to back me up, but as I understand it, the Krebs cycle starts spinning faster under intense exercise. Possibly forcing the cells to give out more energy. Basically, different rules seem to apply under intense exercise. E.g Normally, taking in fructose would stop all energy coming from fat, while the fructose is metabolised into fat. I.e Fructose should be a terrible fuel for a fat adapted athlete. But see below:

HOW TO WIN THE IRONMAN ON LCHF

Bevan had discovered, for himself at least, that once he was well fat adapted, that when he was riding at around 270 W power output then the extra gels didn’t end up dialing down his fat metabolism. He was still around 50% fuel by fat and 50% by carbohydrate. We feel that the whole Kreb’s (fuel) cycle in the body was spinning fast enough and fuel utilisation was high enough that insulin wasn’t being secreted in massive amounts to dial down fat burning and promote glycogen only fuel use. This isn’t what you see in non-fat adapted athletes. Nor is it what you would see in Bevan at rest. This was a key discovery as he could get the performance benefits of the carbs whilst still maintaining the fat burning that he had developed through his LCHF and mainly fasted long aerobic training work.

(ianrobo) #47

But is not the point here about the HR zone u are working under ? In other words burning 4000 at z2 will be totally fat but we keep the carbs back for the efforts at zone 4 and above ?

#48

Under lactate threshold. So mostly fat. And by ‘intense’ I mean - extended.

Even at low intensity, fat adapted athletes will be burning some carbs. A very efficient fat burning adapted athlete might be burning 90% fat/10% carbs or 80/20 at low intensity.

The point being that the energy system does vastly different things at rest and under exercise conditions, and under intense exercise conditions, and that system is largely demand driven.

There is a discrepancy between what Richard has provided in regards to the “daily available fat energy” calculations, and general discussions on available fat energy by people like Prof Phinney. See below:

"What if Tim Olson is just born to run?

STEVE PHINNEY: Some of it is Tim Olson’s inborn, God-given talent as an ultra endurance runner, but some of it has to do with the diet he’s switched to eating – a low-carb diet. We don’t have the details of it, but typically the low-carb runners eat far less during a race. A high carb racer may eat 6,000 in-race calories. But typically a low-carb racer will eat 2000 calories a day during the race, or less. And the better adapted the racer is to low-carb, they find the less they have to eat.

But Olson did eat – so . . . was it glucose gels? Or did he go for butter?

STEVE PHINNEY: Well typically he probably wouldn’t eat butter or fat anyway because this guy is a super slim, highly efficient, fat-burning athlete. He’s got very little body fat, but if let’s say he’s 7% by weight body fat that means he still has at least 30,000 calories of fat in his body when he starts the race.

More Fuel in Fat A 30,000 calorie tank of fuel? On his body?

STEVE PHINNEY: When the starting gun goes off, 30,000 calories of body fat. Now, if you run this race typically your body will burn 10,000 calories over the 100-mile course, so he’s got enough to run the race three times over before runs out of fat fuel. But that’s because he’s a fat-burner. For the carb loaded runners, who are less adapted to burning fat, at the same starting line, even if they’d done their carb loading to the maximum, the most carb calories they’d have in their bodies is 2,000. Now, if you’re running on a carb fuel strategy, and you’ll need 10,000 calories to complete the 100-mile race, that 2,000 calories of carb stored in your body at the start of the race is only 1/5 of the fuel that you need to complete the race.

High-carbers have to fuel up more often?

STEVE PHINNEY: That’s correct. In contrast, if you’re running on a fat fuel strategy, you’ve got three times as much fuel in the tank as you need to complete the race and that’s the beauty, literally the metabolic beauty of the low-carb adapted athlete in an ultra-performance event."

Now if you plug Tim Olsen’s stats into Richards calculator, Tim has probably only got 350 daily fat calories available to him. That doesn’t make any sense, and pretty much negates the usefulness of being fat adapted… So something else is happening. Tim is either accessing many more fat calories, or eating many more fat calories before and during.

My guess is it is the former (or likely both), but it would be great to get Steve Phinney’s and Richard’s views on this matter.

(Erin Macfarland ) #49

YES! This is the issue I have with all the “access to unlimited amounts of energy” BS. You don’t have unlimited access when you have 7% body fat! I have 12 % which for a woman, even an athletic woman, is very low. I can attest that I can go about 16 to 17 hours fasting including a decent workout/run but I feel acutely my energy flagging towards the end of that window. And please see my post from today under exercise which details the active metabolic assessment I just did. I’m burning nearly 100% fat in zones 1 -2 and 65% in zone 5! Pretty cool. So I’m using fat pretty damn efficiently.

#50

I have a pet theory: part of the difference between the rate of fat utilization available in an extended fast (Cahill) vs. fat utilization during endurance exercise lies not only in the difference between the fed and fasted state, but also in the type of body fat being accessed.
For example, visceral fat is easily accessible via the portal vein to the liver, but most athletes will have very little of that. A starvation study subject will have near zero. Both will have some adipose fat, but that is rate limited probably by not only the size, but the absolute number of fat cells. The thing that the athletes do have that starvation subjects don’t have is an abundant supply of intramuscular fat (IMTG). This is part of what endurance training builds up even in non-keto athletes. Muscles have ready access to this during exercise. In fact, I’d be surprised if intramuscular fat is used for basal metabolism at all, in much the same way as the body partitions liver and muscle glycogen in carb burners.

I need to look into this area some more as I doubt much research has been done in fat adapted athletes as to the sources of fat used in long endurance events.

KETO Bonking
#51

Interesting stuff. I first heard of fat-adaptation for endurance sports on a Jimmy Moore podcast interview in Spring of 2008. He was talking to a guy who ran half-marathons and only ate Walmart tubes of ground beef.

I was spurred to try zero carb that summer…I had one BIG flaw…wasn’t aware of the excess protein thing. :open_mouth:

(Erin Macfarland ) #52

Wow!!! Fascinating!! I know my visceral fat is nearly zero. My body fat is 12% which translates to about 12 pounds so not a lot of available energy there. I had no idea about intramuscular fat. Some days I can easily run a 10k and lift weights and not have any problems with energy levels and end up fasting for around 20 hours or so. I notice this is usually possible when I have had high energy intake the day before . I can literally feel my body’s energy stores. It is a strange state to be in when you become a very lean athlete. You are very aware of your body’s signals and are incredibly sensitive to changes in food intake, workout performance , rest, stress. I keep thinking I should be writing this stuff down, the subjective experience of what it feels like to have these responses in my current physical condition . There is not a lot out there regarding how women especially respond to keto and high levels of exercise .

#53

Here’s a study about IMTG in non-keto context.

“The skeletal muscle cell also contains significant quantities of triglyceride. Recent improvements in the ability to measure these intramyocellular triglyceride (IMTG) stores have confirmed that IMTG acts as a significant fuel substrate during prolonged exercise.
…
IMTG formation may be relatively rapid, and its storage predominates under conditions that promote minimal glycogen formation. This observation suggests that the role of IMTG is to maintain a readily available substrate to ensure that physical activity of a moderate nature can be performed when glycogen availability is not optimal. Under these conditions, IMTG may offer a similar availability of energy as glycogen in the endurance-trained athlete.” https://www.ncbi.nlm.nih.gov/pubmed/14987125

#54

Yep. You are a pioneer in this field! Love to see your results. :heart:

(Erin Macfarland ) #55

I raced my first race since trying ZC today, 5 miles. I was able to use my heart rate zones I’d gotten measured in my metabolic assessment that showed I burn a very large percentage of fat even at 80% of my max (normally almost entirely glycolitic for sugar burners) . I came out with a 43 min finish and hit a 7:30 pace several times. Pretty happy with those results. That was fasted as well and didn’t need to eat until a few hours after I finished! So fat is an effective fuel for harder efforts as well!

(Erin Macfarland ) #56

This is awesome

(Alec) #57

Erin
I just found your posted topic as you had EXACTLY the same question as I had. Have read the whole topic, and wow!!

Not sure I am any clearer, but the trail stops over a year ago. What have you learned since then?
Cheers
Alec

(Erin Macfarland ) #58

@Alecmcq I have just received my Certified Personal Trainer designation, and I stil do run though not nearly as much as I did previously. I spent a lot of time in the gym studying for my exam and would get on a cardio machine and read rather than going for a run outside ( I have to multitask I have two kids, lol!) so I’m getting back to running more regularly now. I’m also training for a 150 mile bike ride next month which definitely counts as endurance exercise! I exercise fasted in the mornings, and usually do fine if I’ve slept well and take my electrolytes. But I have off days just like everyone. My diet now is much heavier on the fatty meat than it was when I first speculated about this topic. I had previously tried to “moderate” protein and I found myself ravenous pretty often even after a substantial meal. I did ZC for about 6 weeks and that really helped me get comfortable with eating fatty meat to satiety. I don’t have that gnawing hunger I would get when I would try and moderate protein. I am pretty lean and very active and have no health problems so the higher meat intake seems to work for me. I do eat veggies and dark chocolate and some nuts (my weakness I try to avoid them as much as i can!) but my exercise performance is pretty consistent, I have a lot of lean body mass. So that’s the biggest change I’ve made. Does that help?