Hacker News Reader

Comment by hashberry | Hacker News Reader

Here's a related scientific study that gives a possible reason why: 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).

View on HN

> 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...

> 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.

> 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

You are confusing BMI with body fat percentage.

> You are confusing BMI with body fat percentage.

I understand that they are different things. Unless these are bizarrely jacked ultra-marathoners, BMI should work just fine.

For clarity, you could have just quoted the body fat percentages from the next couple sentences in the abstract.

>> Mean (+/-SD) percent body fat values for men and women were 17+/-5 (range 5-35) and 21+/-6 (range 10-29) , and ranged from 6 to 14 and 14 to 27 among the fastest three men and women.

I would imagine the fastest finishers are not "bizarrely jacked" (they usually look pretty scrawny), but their BMI is not very well correlated with their body fat percentage.

Also this line

> We conclude that despite wide variations in BMI and percent body fat among ultramarathon participants, the faster men have lower percent body fat values than the slower men, and finishers have lower percent body fat values than non-finishers.

So I do stand corrected that not all of them are significantly below 10% body fat, but some definitely were (I don't see a breakdown anywhere giving an indication of how many), including some of the top finishers. I'd also imagine the ones at higher percentages who performed well probably have higher floors to begin with for how little body fat they can reasonably reach.

In any case, it is not at all abnormal for BMI to have nothing to do with body fat percentage or how jacked someone looks, especially with athletes. BMI is probably one of the most meaningless health metrics in common use.

Even further I'd imagine looking at the data for the top 30% of runners who are in the competitive tier this article is talking about would have more relevant and uniform data with narrower ranges.

I've gone to ultras. You really need to have a range for the elites vs. everyone else. It's a very inclusive sport and you have participants that are fairly overweight even. Based on what I recall from my college track days where I knew my teammates' body fat percentages (4% to about 10%) I'd estinate that most elite men are at the lower end of that. Also because most men have more muscle mass their metabolic resting rate is higher so that definitely could be part of the reason why women and men peak performance is so close in ultras. They are using 10 to 15% more calories per hour I'd estimate. Also on a hilly course they need to tote that extra mass up a lot of extra climbs.

I am surprised no one has mentioned Ann Trason that won 13 (iirc) Western States and used to win many ultras outright.

Elite athletes that can't manage their weight so that they have enough body fat to last until the end of the race? I think not. Also, extremely low body fat can cause a host of other issues like low testosterone that could effect race performance.

It's a small sport with not much competition.

BMI is basically useless for people who exercise regularly.

You are assuming that a fat cell can deliver into the bloodstream all of its fat over the course of the ultramarathon. If on the other hand it can deliver only a small fraction of its fat in that amount of time, then the argument in grandparent is saved from your criticism.

The body is sure to put a limit somewhere above zero, and if men are already sub-8% they don’t have much to spare.

Also, women tend to weigh less, so the calories per km is less.

Yea I doubt body fat is the reason. I bet women's bodies just burn less/km than men's. Not just in weight, but also in anatomy. Not just skeletal structure, but muscle composition, etc.

>> Running burns about 100 Calories

Totally depends on the runner. An 85lb female athlete will burn X per km. A 300lb male, covering the same distance/speed, will burn at least 4X and probably 6X.

For the sake of their joints I hope a 300 pound male isn't running long distances.

Seriously doubt there are 300lb dudes running many ultra marathons. I recently read that book by the ex marine dude who did them. He was a freak in the low-mid 200s and he talks about how he destroyed his body pushing thru it. On top of it runners have sugar and whatnot they eat on the way, so op was making a conservative estimate.

Are you talking about https://en.wikipedia.org/wiki/David_Goggins? If so his wikipedia article is fcking hilarious. Someone should coin a term for people who write self-aggrandizing hyperbolic autobiographical wikipedia entries.

Holy shit your comment made me curious about the Wikipedia entry, and boy oh boy were you spot on! Hahahaha

The article may have some strangely worded parts but he seems to be an incredibly strong willed and determined person going from a fat slob gulping down milkshakes (paraphrasing his words) to a seal and an ultra runner.

He was on Joe Rogan at least twice: https://www.youtube.com/watch?v=5tSTk1083VY https://www.youtube.com/watch?v=BvWB7B8tXK8

I was curious so I just read it - even if half of it is true, he’s an incredible individual.

In what way is it hyperbolic?

Thanks for supporting my point lol

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.

Well recent studies have actually found that women have a different catabolism than men. Women also switch to catabolism while they still have glycogen remaining in their muscles, meaning they don't build up as much lactic acid.

This flies in the face of conventional wisdom because all of the original studies were only done on men.

Off the top of my head, I'm not sure if women do have a harder time losing weight than men, but I know that a woman's body reacts to starvation differently. That may play a role.

There is a massive need for "foundational" studies to be redone with women. The assumption that men and women have the same metabolism has been shown to be wrong, and it has a lot of broad and overarching implications, especially in the field of medicine.

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

Very interesting. I assumed that the limit was due to some internal process and hadn't considered maximum CO2 output. Wonder if this means people with larger lung capacity could burn more fat per day.

Sounds dubious, source?

Can you specify what you find dubious?

Anyway, here's the source: 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.

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 :)

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.

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.

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/55b7ffebe4b0568a75e33...

Best book I know of on long-duration effort is this one: https://www.amazon.com/Training-New-Alpinism-Climber-Athlete...

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.

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.

Haven't read Uphill Athlete yet...I think it ships in a few days. Really looking forward to it and to going to see Scott/Steve speak in Denver.

I don't think I'll be able to make any of their talks because the nearest city is a bit away, but I do frequent their forums/site which has an incredible trove of information.

https://www.uphillathlete.com/

Agreed! I love that Scott is so active on there. Those guys are legit.

My other very favorite resource is Shawn Bearden's Science of Ultra podcast, which is where I learned of the research paper I linked in my first post. Here's the one on fat adaptation: https://www.scienceofultra.com/podcasts/19 . He has lots of pretty hardcore exercise scientists and researchers on. It's one of my favorite things to listen to while grinding up a hill. :)

>I could never do that on carb diet.

Have you tried? I always run before eating (not as part of a regimen, it's just convenient), as I expect many do. And my diet is closer to inverse-keto than keto.

It is fascinating to see that I have negative points by simply recounting a bland personal experience. Who did I offend this time? :)

My guess: It appears as though your reason for posting was to say "I could never do that on a carb based diet". However, you never established and reason for that conclusion. Each of us has our personal opinion on a variety of different subjects. We could all post that personal opinion without any corroborating evidence, but because there are a lot of people, this would create a comment section containing mostly noise. People would prefer to see comments based on research or personal experience that seems to strongly corroborate the conclusion. Generally it has been my experience that I do not get many down votes simply because people disagree or are unhappy with what I'm saying. It's usually because I am clearly wrong, or I have simply contributed to the noise.

I think that your comment falls into the noise category and is undesirable because of that. If you had explained personal experiences to show how you reached your conclusion, It think you would get a better reaction. If you also showed how other possibilities could be rules out, then I think people would find it very interesting and you would get many up votes.

Downvoting on HN confuses me. I don't ever downvote anything, I think it's a bad idea. Upvoting is ok, downvoting should be removed.

Also, looking at comments, often I see only upvote and no downvote button. Why is that?

You can only downvote during the first 24 hours, and only comments that are not replies to you.

I don't think that's true for most people. I do weight lifting in the mornings with only a coffee, dinner around 6pm the previous day with no snacks afterwards, and my diet is fairly carby.

I found intermittent fasting hard on carb diet. It is super easy on keto diet. In fast I fast 2-3 days every now and then because it's just a seamless transition.

I'm not saying my personal experience should be considered universal, that'd be foolish. Just recounting that.

But it makes sense given how metabolizing fat and metabolizing sugar works. Insulin response, etc.

Especially in the case of diets, I think personal experience should acccount for most of how you make your decisions. The human body is very flexible to different conditions, the science here is pretty flaky, that trying to make sense of diets by using logic only helps very little. Anyway I'm just repeating what you're saying, that personal experience may not be universal but it's important for yourself.

I think it's more of a mindset thing and what you and your body is used to.

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.

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.

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.

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.

I’m an ultra marathoner; training low carb and racing high gave me best performance at distance and seems to dramatically reduce recovery times.

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.

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.

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)

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

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-w...

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

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

You don't need scientific papers for this.

Just look at the end scores of ultra-marathons.

Reply on news.ycombinator.com