17 ms·

Here's a related scientific study that gives a possible reason why: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4899381/ https://www.ncbi.nlm.nih.gov/pmc/artic

Here's a related scientific study that gives a possible reason why: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4899381/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4899381/ > Women have more body fat than men in both elite (Vernillo et al. 2013) and recreational (Hoffman et al. 2010a, b) athletes. In both elite and recreational runners the percentage of body fat is higher in women compared to men (Blaak 2001). It could be argued that fatty tissue may be used as an energy reserve and this could be an advantage for ultra-distances since runners tend to lose body fat during multi-hours running competitions (Karstoft et al. 2013; Schütz et al. 2013). Women might benefit from their higher percentage of body fat since both sexes lose a similar amount of fat during an ultra-endurance performance such as a 100 km ultra-marathon (Knechtle et al. 2010a, b, 2012a, b).

GreaterFool 7y ago
Sounds reasonable to me. I've been eating keto for a long time and I always feel like I have fat energy reserves to draw on. I wonder if keto-adapted men and women would outperform carb-adapted counterparts in ultra-endurance. From personal experience there is a difference and it is a big difference.
- Mountain_Skies 7y ago
  The body can only convert so much fat into energy at a given moment. Usually we have both carbs we've recently eaten to fuel us plus a store of glycogen. On Keto you should have little to no glycogen and only whatever small number of carbs you've eaten recently. If your energy expenditure exceeds what they body can convert from fat along with whatever it can extract from your limited carbs and whatever glycogen is hanging around, you'll get an energy crash. Keto might be good for ultra endurance events where there is little to no sprinting involved. Just keep a nice steady pace at the level that can be fueled by the body's capacity to convert fat into energy.
  - stefan_ 7y ago
    Except then you would still eat carbs the night before a race because not having glycogen is just intentionally gimping yourself for no imaginable possible gain. It's not like the mj of glycogen energy is weighing you down. You should absolutely train in a glycogen depleted state just so you will know what it feels like and can deal with it. But it's not how you would ever start a race.
  - mdhen 7y ago
    Yeah doing a lot of anaerobic activities when on a zero or Ultra low carb diet will tend to wear you out quicklydue to glycogen depletion.
- crikli 7y ago
  Researchers have not seen any evidence that the ketogenic diet (or any other diet that trains the body to engage lipolysis to a greater degree) increases exercise capacity. They have seen evidence that these diets can retool the body to more readily use fat as an energy substrate. While this doesn't translate to performance gains, it can mean that on a multi-hour/multi-day effort that a self-supported athlete might need to have a bit less food in their packs as well as foods with a higher proportion of fat that are lighter. Lighter pack = faster athlete. But...even low intensity exercise over long duration is going to result in the recruitment of FTa/FTb muscle fibers that run almost exclusively by glycolyis. So an athlete counting on fat to be the primary energy substrate has be really highly trained, practiced, and know their pacing thresholds really well to keep the recruitment of those muscle fibers to a minimum. Best paper I know of on the subject is this one: https://static1.squarespace.com/static/55b7ffebe4b0568a75e3316b/t/569ff94e42f552509507b7b9/1453324628174/Burke+review+fat+adaptation.pdf https://static1.squarespace.com/static/55b7ffebe4b0568a75e33... Best book I know of on long-duration effort is this one: https://www.amazon.com/Training-New-Alpinism-Climber-Athlete-ebook/dp/B00ILZ8S0K https://www.amazon.com/Training-New-Alpinism-Climber-Athlete...
  - GreaterFool 7y ago
    I can only speak to my personal experience. I’m not an athlete but I lift, bike and so on. On empty stomach. I don’t eat before training. I could never do that on carb diet.
    - evandev 7y ago
      Speaking from my personal experience to counter this, I run in the mornings up to 1 hour on an empty stomach. While I don't follow one diet, a larger portion of my food is carb based. I follow TFTNA (Training for the New Alpinism) and Uphill Athlete (Steve/Scott's new book) training regiments that Parent mentions. They do talk about retooling your body to use fat reserves more than carbs. While I'm sure the evidence shows that keto diet might make this switch faster and easier, someone on a non-keto diet (carb based) can also do this.
      - 7y ago
- thrav 7y ago
  There is a world record holder for 1000 mile races who is all about running off only fat. Advises to eat nothing before the race, and to refuse all of the gu and gels they try to hand you while running. I successfully completed a marathon 3 months after reading his book after having never run more than 3 miles in my life. (Stu Mittleman - Slow Burn)
- ErikAugust 7y ago
  There are a couple examples: Zach Bitter (50 mile - 24 hour races) and Tim Olson (100 mile trail). Both have held notable records. In the marathon distance or shorter, being fat adapted would be a bad thing, as you couldn't train at upper capacities. But where you are running purely aerobically for very long periods of time (12+ hours), this may be an advantage. The secondary (or even primary) advantage would be a low carb or ketogenic diet is that it is anti-inflammatory. People who run ultra distances do huge volumes of training, and it may be enabled by a lack of inflammation.
- tedmcory77 7y ago
  I’m an ultra marathoner; training low carb and racing high gave me best performance at distance and seems to dramatically reduce recovery times.
- drdrey 7y ago
  Some elite ultrarunners are on LCHF diets, like Zach Miller, Timothy Olson or Jeff Browning. I don't think any of them are on the keto diet specifically. But the vast majority of them are on the typical high-carb runner diet.
- nasmorn 7y ago
  No. But modern training methods include fasted workouts to improve fat metabolism. If you are ok with sub maximal performance keto can be a good way to reach it as the highest keto fat burning is higher than when you use carbs as well. the absolute performance is quite a bit better if you consume carbs though.
j7ake 7y ago
On a related note, open water long distance swimming is often a sport where women are at the top.
- aodin 7y ago
  Women's dominance of open water long distance swimming is mostly from the higher natural buoyancy of body fat rather than any sex specific ketogenic effects. https://www.thecut.com/2016/09/the-obscure-endurance-sport-women-are-quietly-dominating.html https://www.thecut.com/2016/09/the-obscure-endurance-sport-w...
Mountain_Skies 7y ago
It is my understanding that humans generally are limited to converting about 0.8% of the body fat into usable energy per day. If women generally have more body fat, then they would be able to yield more energy from it before hitting the 0.8% limit (which likely is spread out over the day especially in endurance events). Or there might even be some variance in that 0.8% limit, with women being able to convert a bit more per day than men. This would fly in the face of the conventional wisdom that women have a more difficult time losing weight than men. Certainly would be an interesting possibility to study.
- gilbetron 7y ago
  Sounds dubious, source?
  - Mountain_Skies 7y ago
    Can you specify what you find dubious? Anyway, here's the source: https://www.ncbi.nlm.nih.gov/pubmed/15615615 https://www.ncbi.nlm.nih.gov/pubmed/15615615 It states the maximum conversion is (290+/-25) kJ/kgd. It's been a while since I last worked on this subject but I believe that works out to somewhere in the range of 0.8% to 1% of body fat that can be converted into energy per day at most. Of course there were some experimental controls in the study that don't always map exactly into the real world. There always are but this should be close enough for the discussion here.
    - gilbetron 7y ago
      Thanks for the source! Jumping from that study (which is tightly focused) into the statistic of "0.8% body fat per day limit" is dubious, and "close enough" doesn't work with nonlinear systems like the our bodies. Read many of the threads around discussing that article for more information :)
- tejtm 7y ago
  My layman's understanding is - fat burning results in CO2 - CO2 is only removed by exhaling - we exhale ~about~ 2lbs of CO2 per day - fat burning is limited by the amount we can exhale note: this does not claim one can only burn 2lbs of fat/day only that resulting CO2 from burning some amount of fat must fit in the exhaling budget
cm2012 7y ago
I've read that historically on Jeju Island in South Korea, women were the breadwinners for the longest time. This was because the most valuable thing peasants could do was dive for shellfish. Women could do it better than men since their level of body fat gave them more protection from the cold, etc.
nordsieck 7y ago
> Women might benefit from their higher percentage of body fat since both sexes lose a similar amount of fat during an ultra-endurance performance such as a 100 km ultra-marathon (Knechtle et al. 2010a, b, 2012a, b). Sounds like BS to me. Running burns about 100 Calories / mile[0] (62.5 Calories / km). 100 km means 6250 Calories burned. Fat is 9 Calories per gram, so 6250 Calories is 1.5 lbs (0.694 kg) of fat. Even if the calorie burn rate is way off - say by 50%, there is no way any of those athletes is in danger of running out of body fat. And that doesn't even count the carb gels and other food runners typically eat on runs. ___ 0. https://www.runnersworld.com/nutrition-weight-loss/a20784289/the-burning-question/ https://www.runnersworld.com/nutrition-weight-loss/a20784289...
- eredengrin 7y ago
  > Running burns about 100 Calories / mile[0] (62.5 Calories / km). Okay, at least that blog post is written by someone with a phd, but you can't really take this at face value either. It's probably reasonably true in general (obviously still highly dependent on the person doing the running), but you seem to be assuming that this rate is the same on short runs and long runs, which sound suspicious. I wouldn't at all be surprised if the rate of energy expenditure increased as the time/distance of the race increased. Also if they're running instead of sleeping, I imagine that is probably increasing energy use as well. I'd also be pretty surprised it the 100 calories/mile was taking into account the person's resting metabolic rate. That could easily add another one to two thousand (more depending on the person) calories per day. Finally, even with your analysis coming to 1.5lbs of fat, that's quite a lot of fat in a trained athlete. I'd expect most of the men running these races are well below 10% body fat, and the lower your body fat is the more resistant the body tends to be when it comes to losing more. Losing 1.5 or more lbs of fat would probably be moving their body fat percentages down quite noticeably, which is not easy to do at such low levels. So maybe it is all bs, but I don't think it can be ignored so easily either.
  - nordsieck 7y ago
    > I'd expect most of the men running these races are well below 10% body fat You're way off > This study compares body composition characteristics with performance among participants in a 161-km trail ultramarathon. ... Mean (+/-SD) BMI (kg x m(-2)) was 24.8+/-2.7 (range 19.1-32.2) for the men and 21.2+/-2.1 (range 18.1-26.7) for the women. Among the three fastest runners, BMI values ranged from 22.1 to 23.4 for men and 21.5 to 22.9 for women. [0] ___ 0. https://www.ncbi.nlm.nih.gov/pubmed/20222002 https://www.ncbi.nlm.nih.gov/pubmed/20222002
stefan_ 7y ago
Except any walking person has enough body fat to sustain multiple 100 km ultra marathons worth of energy?
- mertd 7y ago
  They don't have the muscles and cardio to tap into and burn the fat as efficiently.
NicoJuicy 7y ago
You don't need scientific papers for this. Just look at the end scores of ultra-marathons.

GreaterFool 7y ago

Sounds reasonable to me. I've been eating keto for a long time and I always feel like I have fat energy reserves to draw on. I wonder if keto-adapted men and women would outperform carb-adapted counterparts in ultra-endurance. From personal experience there is a difference and it is a big difference.

Mountain_Skies 7y ago
The body can only convert so much fat into energy at a given moment. Usually we have both carbs we've recently eaten to fuel us plus a store of glycogen. On Keto you should have little to no glycogen and only whatever small number of carbs you've eaten recently. If your energy expenditure exceeds what they body can convert from fat along with whatever it can extract from your limited carbs and whatever glycogen is hanging around, you'll get an energy crash. Keto might be good for ultra endurance events where there is little to no sprinting involved. Just keep a nice steady pace at the level that can be fueled by the body's capacity to convert fat into energy.
- stefan_ 7y ago
  Except then you would still eat carbs the night before a race because not having glycogen is just intentionally gimping yourself for no imaginable possible gain. It's not like the mj of glycogen energy is weighing you down. You should absolutely train in a glycogen depleted state just so you will know what it feels like and can deal with it. But it's not how you would ever start a race.
- mdhen 7y ago
  Yeah doing a lot of anaerobic activities when on a zero or Ultra low carb diet will tend to wear you out quicklydue to glycogen depletion.
crikli 7y ago
Researchers have not seen any evidence that the ketogenic diet (or any other diet that trains the body to engage lipolysis to a greater degree) increases exercise capacity. They have seen evidence that these diets can retool the body to more readily use fat as an energy substrate. While this doesn't translate to performance gains, it can mean that on a multi-hour/multi-day effort that a self-supported athlete might need to have a bit less food in their packs as well as foods with a higher proportion of fat that are lighter. Lighter pack = faster athlete. But...even low intensity exercise over long duration is going to result in the recruitment of FTa/FTb muscle fibers that run almost exclusively by glycolyis. So an athlete counting on fat to be the primary energy substrate has be really highly trained, practiced, and know their pacing thresholds really well to keep the recruitment of those muscle fibers to a minimum. Best paper I know of on the subject is this one: https://static1.squarespace.com/static/55b7ffebe4b0568a75e3316b/t/569ff94e42f552509507b7b9/1453324628174/Burke+review+fat+adaptation.pdf https://static1.squarespace.com/static/55b7ffebe4b0568a75e33... Best book I know of on long-duration effort is this one: https://www.amazon.com/Training-New-Alpinism-Climber-Athlete-ebook/dp/B00ILZ8S0K https://www.amazon.com/Training-New-Alpinism-Climber-Athlete...
- GreaterFool 7y ago
  I can only speak to my personal experience. I’m not an athlete but I lift, bike and so on. On empty stomach. I don’t eat before training. I could never do that on carb diet.
  - evandev 7y ago
    Speaking from my personal experience to counter this, I run in the mornings up to 1 hour on an empty stomach. While I don't follow one diet, a larger portion of my food is carb based. I follow TFTNA (Training for the New Alpinism) and Uphill Athlete (Steve/Scott's new book) training regiments that Parent mentions. They do talk about retooling your body to use fat reserves more than carbs. While I'm sure the evidence shows that keto diet might make this switch faster and easier, someone on a non-keto diet (carb based) can also do this.
    - 7y ago
thrav 7y ago
There is a world record holder for 1000 mile races who is all about running off only fat. Advises to eat nothing before the race, and to refuse all of the gu and gels they try to hand you while running. I successfully completed a marathon 3 months after reading his book after having never run more than 3 miles in my life. (Stu Mittleman - Slow Burn)
ErikAugust 7y ago
There are a couple examples: Zach Bitter (50 mile - 24 hour races) and Tim Olson (100 mile trail). Both have held notable records. In the marathon distance or shorter, being fat adapted would be a bad thing, as you couldn't train at upper capacities. But where you are running purely aerobically for very long periods of time (12+ hours), this may be an advantage. The secondary (or even primary) advantage would be a low carb or ketogenic diet is that it is anti-inflammatory. People who run ultra distances do huge volumes of training, and it may be enabled by a lack of inflammation.
tedmcory77 7y ago
I’m an ultra marathoner; training low carb and racing high gave me best performance at distance and seems to dramatically reduce recovery times.
drdrey 7y ago
Some elite ultrarunners are on LCHF diets, like Zach Miller, Timothy Olson or Jeff Browning. I don't think any of them are on the keto diet specifically. But the vast majority of them are on the typical high-carb runner diet.
nasmorn 7y ago
No. But modern training methods include fasted workouts to improve fat metabolism. If you are ok with sub maximal performance keto can be a good way to reach it as the highest keto fat burning is higher than when you use carbs as well. the absolute performance is quite a bit better if you consume carbs though.

j7ake 7y ago

On a related note, open water long distance swimming is often a sport where women are at the top.

aodin 7y ago
Women's dominance of open water long distance swimming is mostly from the higher natural buoyancy of body fat rather than any sex specific ketogenic effects. https://www.thecut.com/2016/09/the-obscure-endurance-sport-women-are-quietly-dominating.html https://www.thecut.com/2016/09/the-obscure-endurance-sport-w...

Mountain_Skies 7y ago

It is my understanding that humans generally are limited to converting about 0.8% of the body fat into usable energy per day. If women generally have more body fat, then they would be able to yield more energy from it before hitting the 0.8% limit (which likely is spread out over the day especially in endurance events). Or there might even be some variance in that 0.8% limit, with women being able to convert a bit more per day than men. This would fly in the face of the conventional wisdom that women have a more difficult time losing weight than men. Certainly would be an interesting possibility to study.

gilbetron 7y ago
Sounds dubious, source?
- Mountain_Skies 7y ago
  Can you specify what you find dubious? Anyway, here's the source: https://www.ncbi.nlm.nih.gov/pubmed/15615615 https://www.ncbi.nlm.nih.gov/pubmed/15615615 It states the maximum conversion is (290+/-25) kJ/kgd. It's been a while since I last worked on this subject but I believe that works out to somewhere in the range of 0.8% to 1% of body fat that can be converted into energy per day at most. Of course there were some experimental controls in the study that don't always map exactly into the real world. There always are but this should be close enough for the discussion here.
  - gilbetron 7y ago
    Thanks for the source! Jumping from that study (which is tightly focused) into the statistic of "0.8% body fat per day limit" is dubious, and "close enough" doesn't work with nonlinear systems like the our bodies. Read many of the threads around discussing that article for more information :)
tejtm 7y ago
My layman's understanding is - fat burning results in CO2 - CO2 is only removed by exhaling - we exhale ~about~ 2lbs of CO2 per day - fat burning is limited by the amount we can exhale note: this does not claim one can only burn 2lbs of fat/day only that resulting CO2 from burning some amount of fat must fit in the exhaling budget

cm2012 7y ago

I've read that historically on Jeju Island in South Korea, women were the breadwinners for the longest time. This was because the most valuable thing peasants could do was dive for shellfish. Women could do it better than men since their level of body fat gave them more protection from the cold, etc.

nordsieck 7y ago

> Women might benefit from their higher percentage of body fat since both sexes lose a similar amount of fat during an ultra-endurance performance such as a 100 km ultra-marathon (Knechtle et al. 2010a, b, 2012a, b). Sounds like BS to me. Running burns about 100 Calories / mile[0] (62.5 Calories / km). 100 km means 6250 Calories burned. Fat is 9 Calories per gram, so 6250 Calories is 1.5 lbs (0.694 kg) of fat. Even if the calorie burn rate is way off - say by 50%, there is no way any of those athletes is in danger of running out of body fat. And that doesn't even count the carb gels and other food runners typically eat on runs. ___ 0. https://www.runnersworld.com/nutrition-weight-loss/a20784289/the-burning-question/ https://www.runnersworld.com/nutrition-weight-loss/a20784289...

eredengrin 7y ago
> Running burns about 100 Calories / mile[0] (62.5 Calories / km). Okay, at least that blog post is written by someone with a phd, but you can't really take this at face value either. It's probably reasonably true in general (obviously still highly dependent on the person doing the running), but you seem to be assuming that this rate is the same on short runs and long runs, which sound suspicious. I wouldn't at all be surprised if the rate of energy expenditure increased as the time/distance of the race increased. Also if they're running instead of sleeping, I imagine that is probably increasing energy use as well. I'd also be pretty surprised it the 100 calories/mile was taking into account the person's resting metabolic rate. That could easily add another one to two thousand (more depending on the person) calories per day. Finally, even with your analysis coming to 1.5lbs of fat, that's quite a lot of fat in a trained athlete. I'd expect most of the men running these races are well below 10% body fat, and the lower your body fat is the more resistant the body tends to be when it comes to losing more. Losing 1.5 or more lbs of fat would probably be moving their body fat percentages down quite noticeably, which is not easy to do at such low levels. So maybe it is all bs, but I don't think it can be ignored so easily either.
- nordsieck 7y ago
  > I'd expect most of the men running these races are well below 10% body fat You're way off > This study compares body composition characteristics with performance among participants in a 161-km trail ultramarathon. ... Mean (+/-SD) BMI (kg x m(-2)) was 24.8+/-2.7 (range 19.1-32.2) for the men and 21.2+/-2.1 (range 18.1-26.7) for the women. Among the three fastest runners, BMI values ranged from 22.1 to 23.4 for men and 21.5 to 22.9 for women. [0] ___ 0. https://www.ncbi.nlm.nih.gov/pubmed/20222002 https://www.ncbi.nlm.nih.gov/pubmed/20222002

stefan_ 7y ago

Except any walking person has enough body fat to sustain multiple 100 km ultra marathons worth of energy?

mertd 7y ago
They don't have the muscles and cardio to tap into and burn the fat as efficiently.

NicoJuicy 7y ago

You don't need scientific papers for this. Just look at the end scores of ultra-marathons.