Fasted Exercise.

[W I S N E R !]

Whether short and fast or long and slow, I’ve been experimenting with fasted exercise for a couple years now. This includes long surf sessions, backpacking, trail running, and cycling.  I’ve read quite a bit on adapting to sugar vs. fat burning and vice versa (Cordain, Mark Sisson, Ben Greenfield, and Mark Allen’s triathlon training being my main sources of the pro-fat burning kool aid).

Some personal experiences:

While I’m not “low” or “no” carb in diet, it seems to me that fasted exercise alone might shift you into fat burning during exertion. I’m suspecting that even without a low-carb diet, I might be on the fat burner side of the scale…or I possibly just have massive glycogen stores, as I can go pretty long and hard on no food.

This became apparent to me again on a 75 mile road ride with a few friends this weekend.  I had no breakfast and nothing but a banana about 3 hours into the event.  Which is typical for me.  Whereas I noticed they were eating constantly…big breakfasts, bars and gels every 30 minutes or so, and a big lunch.  NUUN supplements as well as Perpetuem in their water.  Honestly, I thought it was a bit overkill.  We finished at a BBQ and they were ravenous.  My hunger didn’t set in until much later in the day.  It became apparent to me that while I’ve been training to avoid food during exercise, I think they’ve been training themselves to need it.  Whether this is partially mental, I have no idea.

Two days before that, I did a strenuous 15 mile hike in just under 6 hours.  Lot’s of elevation, off trail…same deal, no breakfast, trail mix during one rest stop, water.

Today was a fairly high intensity cyclocross workout that lasted an hour at about 8AM.  No breakfast, just water, and I still haven’t eaten.

Don’t get me wrong, I’m no skinny guy; I definitely make up the calories later

In my early days of getting into distance sports, I was an eater just like the people I mention above.  I couldn’t go without my gels and bars and drinks and I’ve had some pretty massive bonks during marathons.   But somewhere along the line I stopped, around the time I was reading a lot about Mark Allen’s low-carb training and fasting for fat burning in IronMan events.

Needless to say, it’s incredibly convenient as an athlete, especially backpacking.  Fewer stops, less food to carry.  It’s also very beneficial on the pocketbook; being able to ride 100 miles on a banana and a bar and a few water bottles is so much easier.

I realize that there is no one size fits all here; some are likely naturally adapted in one way or the other or see no need to pursue one or the other.  But I suspect that the fasted exercise has adapted me over time.

I’m curious if others have any thoughts or experience with this.

[W I S N E R !]

I also have to question if the supplement/energy bar/gel/drink industry has skewed our perspective about what’s actually necessary during exercise, obviously skewing it in their own favor.

[Pedestrian]

My experience is very similar to yours except that I also tend to eat very low carbs and high fat  (LCHF) most of the time.

For a few years now (before going LCHF almost fifteen months back), I’ve been doing most of my long hikes/runs fasted; once my system adapted to going longer without any calories, I feel no hunger until about five-six hours in to the hike. This is mostly hiking up hills with a pack at a good clip. If I’m going longer than five hours I’ll eat something (macadamia nuts, meat bars, jerky, salami, but very few carbs). Longest I’ve gone is 20+ miles with 6000 ft+ elevation gain in under seven hours eating a “lunch” (salami, some nuts) about four hours in to the hike and felt no hunger pangs during or immediately after the hike. I do drink chicken stock (powdered chicken bouillon dissolved in water) to replace lost sodium and take a magnesium supplement as I tend to cramp especially on warm days.

I was climbing Mt Shasta last weekend with almost no sleep the previous night and almost no carbs but had to bail up near the Red Banks – I was overcome with sleep and I wondered if lack of carbs may also have contributed. Climbing up to the summit (~14100 ft) from Horse Camp (our starting point, ~7950 ft)) entails about ~6500 ft of elevation gain in about 4 miles much of it in the snow even at this time of year. I didn’t feel fatigued nor hungry and had no altitude symptoms – I just was dozing off as I walked – I was concerned I might slip and fall and not be able to self-arrest so I just headed down hill; the weather also had turned nasty past Red Banks.

To summarize : until this past weekend I never experienced any “bonk” in the fasted state eating mostly fat and protein five plus hours into the hike. Given that I barely slept the night before  – bad mosquitoes and very warm weather (we woke up at 1 am and started walking to the summit before 2 am, having driven up from the Bay Area around 5 pm the previous evening), I’m not sure if it was mainly the sleep deprivation or if the fasted/low carb state that contributed my symptoms.

NOTE: I’ve done several long (20+ mile, 6000+ ft) hikes in a sleep deprived state over the years (don’t ask why ;)); even if I started out hiking feeling sleepy, the sleepiness would be gone after the first hour or so. It would then be like I was fully rested before the hike. This time I found myself dozing while walking uphill three hours into the hike – something new for me. That’s why I wonder if the fasted/low carb state contributed to my symptoms; Mt Shasta is also a pretty serious butt kicker as I found out last weekend.

I’ll try the same hike next year again  (with more sleep) and report back ;).

 

 

[BlackHatGuy]

I tend to eat and drink less than most when I’m backpacking/riding/whatever. Doesn’t seem to affect my performance any. I don’t really do fasted exercise, as I have a ProBar meal for breakfast, but that might be it until dinner. I carry two ProBar minis to eat during the day, but don’t always eat them, and rarely eat both of them. I’ve never had a trip where I didn’t bring food home.

[Roger Caffin]

I also have to question if the supplement/energy bar/gel/drink industry has skewed our perspective about what’s actually necessary during exercise, obviously skewing it in their own favor.

You don’t have to ask. It is blazingly obvious. Always remember: we (or our parents) used to go walking very happily before these industries existed. Those industries would not exist if they did not manage to persuade you (by whatever methods) that you should open your wallet.

If you have the energy reserves inside your body and you have trained your body to be able to supply the energy you need from those reserves – you are good to go. And a survivor.

It is also worth noting that eating while you are walking may not be a good idea anyhow. Eating diverts part of your blood supply to your stomach and guts – away from your muscles. Trying to exercise too hard while you are eating may produce nausea and vomiting.

Cheers

 

[Ryan K]

I have found as I have increased my average hiking speed, I tend to eat less.  I just don’t feel as hungry, which I concluded was because the faster pace makes my stomach more upset and stops sending hunger signals to my brain – I don’t know.  But I do feel my energy lag a bit if I don’t try to eat something every couple hours or so.  And then if I reach a resupply point with real food available, I’m suddenly super-hungry again.  I read a ton about doing a high-fat keto-diet and trying to promote fat burning – tried it for a short bit but that type of diet just doesn’t appeal to me, especially since I’m mostly vegan.   I think that unless you’re running, you’re unlikely to use up your glycogen stores (I understand you need some glycogen to help you burn fat), which means that most everyone has enough fat stores and capability to burn those fats for energy while on the move, for a multi-day hike with very little food.  Most of it is mind over matter – if you are committed to not eating and can ignore hunger pains and still enjoy your hike, then you can probably do it.  Determining how much food you need to take on a multi-day hike is much more about determining your personal balance of energy level/hunger threshold/food preference than whatever the sports scientists/food industry tells you you need to consume.

[Valerie E]

I think it’s genetics.  Pure and simple.

I routinely do “fasted exercise”, but not on purpose.  When I wake up in the morning, I don’t feel hungry (ever) and if I try to shove food down my throat anyway, I become extremely nauseated.*  Horrible feeling.  So, since I do most of my exercise in the morning, it’s while fasting.  I’ve always performed very well in this state, and often don’t eat until I’m 5 or more miles into my hike (or run).  And for many years, I didn’t have a spare pound on me, so I wasn’t burning excess fat.

My husband, on the other hand, has to eat constantly (which is kind of annoying for those who don’t want to eat, and want to keep going, LOL).

* After years of symptoms, I’ve finally been diagnosed with a GI condition that explains this, but fortunately I’m still able to exercise effectively in a fasted state.

[Nick Gatel]

Yeah, probably genetics plus some conditioning. I doubt early hunters/gathers ate 3 squares a day. Most days I just eat one meal – dinner, and a banana for breakfast. Backpacking I usually eat a bit of oatmeal for breakfast, only snack when hungry, and then eat dinner. When I was in high school I never ate breakfast, spent my lunch money on my stamp collection, and ate a small dinner — I was a distance runner and often ran 80 miles per week. However, I can’t do a multi-week backpacking trek without upping my consumption considerably. Sometimes I think we get too consumed with the science of sports as it relates to nutrition. Probably different for world class athletes like Michael Phelps or Galen Rupp. I read a few years ago that Phelps consumes thousands of calories a day. Rupp’s training this year has been 140 miles a week and he literally eats, runs, sleeps, eats, runs again, and sleeps.

[Roger Caffin]

Rupp’s training this year has been 140 miles a week and he literally eats, runs, sleeps, eats, runs again, and sleeps.

How boring. Perhaps he needs to get a life?

Cheers

[Nick Gatel]

Rupp came in 1st for the marathon in the Olympic Trials (the first marathon he ever ran), then he came in first in the Trials 10K run (he won the Silver Medal in London in 2012). Saturday he runs the 5K in the Trials. I doubt he is bored :)

 

[John S.]

Mostly mental in the case of not eating much of day until after strenuous exercise. If you didn’t lose weight, you are just overeating later on to maintain your weight. It is not rocket science. Some cannot do that since they may be susceptible to hypoglycemia (me).

[John S.]

Rupp may have more to worry about.

https://www.propublica.org/article/former-team-members-accuse-coach-alberto-salazar-of-breaking-drug-rules

[W I S N E R !]

There’s more going on than just perception. While my experiences and reading tell me that the mental aspect might make someone feel more or less comfortable, to an extent, with or without food, there’s also a very physical component: if you burn more calories than you’re consuming and cannot make up for it with glycogen stores or shifting to body fat, you’re going to end up a shaking mess on the floor.

Conventional wisdom on the matter is that in order to shift into a fat burning mode, you need to adapt to a LCHF diet, as well as practice fasted exercise.  But again, my experiences raise the following questions:

A.  Is it possible to shift over into fat burning by merely practicing fasted exercise despite not eating LCHF regularly?

B.  Perhaps my glycogen stores are bigger than I realize and I still am burning sugar, even when fasted?

C. Perhaps I’ve simply become more efficient at long slow distance and I’m not burning the calories I used to?

D.  Perhaps some people, regardless of diet, are already leaning toward the fat burning end of the spectrum and don’t need a constant sugar supply.

Just pondering the fact that I used to have to eat massive amounts during long events (50K+ mountain hikes/runs,  200+ mile road cycling events, 10+ hour MTB races) in order to not bonk.  I don’t have to eat nearly as much anymore, and I’m questioning if it might be due to a shift into fat vs. sugar burning.  Because based on previous experiences, the calories I’m burning vs. consuming during events don’t seem to add up to avoid a bonk.

[W I S N E R !]

I’m excited to watch Rupp run this year Nick.  The 5K and up are my favorite trials/olympic events.

[Nick Gatel]

Yeah John, I’ve been following that for a while. Right now everyone is kind of backing off because some of the claims are really iffy. If Rupp cheated he needs to suffer the consequences and I have no respect for Alberto anyway.

Magness has always had a bad attitude towards much of the sport. I followed his career as he was a contemporary of my son. In high school Magness ran the 7th fastest high school mile in history and many predicted he would become the next great American distance runner, which never happened. He really was a head case and never reached his potential because he thought he was smarter than his coaches. Surprisingly, after his self-induced training errors, he has become a pretty good distance coach. Perhaps some of this is sour grapes on his part.

Rupp is also a contemporary of my son, so I have followed him closely too. Many in the running world have hated Rupp since he was a freshman in high school. The messages boards on letsrun.com have been historically vile towards him. I don’t know of any runner in this country who has worked harder at the sport than Galen Rupp has during the past 15 years or so.

[Pedestrian]

Some very interesting questions about LCHF, fasted exercise, fat burning.

I urge anyone interested in LCHF to look at the the books and research published by Stephen Phinney and Jeff Volek. Also look at the link below for a wealth of information about LCHF.

Low Carb Down Under

My limited experience over the past fifteen months or so with LCHF has been very positive; but it is an ongoing struggle to eat LCHF: the best I’m able to do is maintain “shallow” ketosis. More than the just temptation to eat breads and desserts etc, it is sometimes hard socially when out for a meal with friends or colleagues.

Before we look at each of the questions raised it’s important to look at some of the findings from research and experience with ketogenic diets generally. The following is what I understand; I’m happy to be corrected and to learn from others’ experience:

• there appears to be significant individual variability in carbohydrate sensitivity – some people suffer from metabolic syndrome one of the symptoms of which is elevated insulin levels in response to carb ingestion – over time this leads to insulin resistance and eventually to type 2 diabetes. At the other end of the spectrum are people who have a “normal” insulin response and have no trouble metabolizing carbs – storing the carbs as glycogen and using the glycogen to fuel any physical effort. There is a very wide spectrum of response to carbs in the human population; it could be genetic or could be moderated by behavior: diet, exercise and other physiological factors.
• one way to know if you’re truly in a ketogenic state (simplistically fat burning state) is to measure your blood ketones (actually betahydroxybutarate) using a meter. If your reading is above 1.0 or above, you’re likely in nutritional ketosis and your body is operating on ketones.
• it is difficult for most people to enter and stay in nutritional ketosis if they at all ingest significant carbs; it can initially take 2-3 weeks of being on a LCHF diet to achieve ketosis and each time you do subsequently ingest carbs, it can take up to a week to get back to ketosis. It’s like walking on a knife edge. If you’re at all insulin resistance you’re likely to struggle to achieve and maintain ketosis even with very small amounts of carbs in the diet – in some cases more than 10 grams of carbs a day can be too much. Exercising in a fasted state does help in achieving and staying in ketosis.

Now let’s look at the questions raised above in turn:

“A. Is it possible to shift over into fat burning by merely practicing fasted exercise despite not eating LCHF regularly?”

Maybe if you’re genetically predisposed to being highly insulin sensitive.

B.  Perhaps my glycogen stores are bigger than I realize and I still am burning sugar, even when fasted?

Perhaps you have bigger glycogen stores; one way to know if you’re burning fat (operating on ketones) is to check your blood ketone level.

C. Perhaps I’ve simply become more efficient at long slow distance and I’m not burning the calories I used to?

This is a different way of saying that you’re keto adapted.

D.  Perhaps some people, regardless of diet, are already leaning toward the fat burning end of the spectrum and don’t need a constant sugar supply.

Indeed these are the folks who could sustain nutritional ketosis even in the presence of carbs in the diet.

 

[Ryan K]

I drank the keto kool-aid and then threw up, metaphorically speaking, so I’m a bit biased.  I don’t intend to start a big argument about LCHF/”paleo”/ketogenic diets, I know there are some top ultrarunners performing well in ketosis, and if you happen to be a person that gets elevated insulin levels when eating a health high carb diet but miraculously doesn’t when eating LCHF, then some form of LCHF may be a better diet for you, but for most people, I believe a whole-food plant-based diet high in carbs is the best lifestyle choice, and I personally want my training diet to be the same as my normal diet, and as close to my hiking diet as possible.

I would recommend anyone following this thread to research this yourself and form your own opinion, but here’s a good video about how paleo or meat-heavy diets may produce higher insulin levels, from one of the only nutrition scientists I trust:

http://nutritionfacts.org/video/paleo-diets-may-negate-benefits-of-exercise/

So I’m in agreement with Craig.  Training with moderate-intensity, long-distance fasted hiking may be sufficient.  Your body goes into starvation mode and starts burning stored fat for energy, but you have none of the negatives of an LCHF diet.  But I think your body goes into starvation mode with little prior fasted training or lucky genetics – the training part is learning not to feel starving when you’re doing it.

 

 

[Roger Caffin]

the training part is learning not to feel starving when you’re doing it.

Does this mean “you are still miserable, but you just don’t know you are”?
:-)

Cheers

[Ryan K]

“you are still miserable, but you just don’t know you are”?

= hiking  :P

When I’m running up a mountain, my legs and lungs are saying “WTF!?” and my mind is singing “La la la, this is effing awesome, I can’t hear you.”  Now I just need to learn to tell my stomach to shut up too, and I can be <10# including food.

[W I S N E R !]

I’m with you on this Ryan; I really don’t have interest in a highly animal-based diet.   That’s why I’m so interested in the possibility of fasted exercise giving some of the same benefits as LCHF diets.

[Anonymous]

Similar experiences as Craig, Pedestrian, Doug, etc.

Hard to say for certain, but my guess is that it tends to be about 3 parts physical adaptation and conditioning, 2 parts mental-emotional/beliefs/perception/habit and 1 part genetic (so much gets attributed to genetics nowadays, anything we don’t fully understand or perceive clearly seems to be automatically labeled as “genetic” in cause.  Don’t agree based on experience with so called purely caused genetic health issues like psoriasis, which i’ve successfully treated with diet, exercise and lowering stress).

I think it also helps if you have some extra fat stores.  I’ve noticed that generally, very skinny/low body fat people tend to eat more or want to eat more while active.

Once we started tapping into our fat reserves on this last trip, i was surprised at how we were not usually ravenous despite eating so little for most of the day and expending so much energy.  One day a few weeks in, one of our longest mile days, we shared a Nature Valley’s granola bar for breakfest (bad planning), and around lunch shared a coconut sugar/whey/salt shake.  Typically only our dinners were more full meals and not always.

However, the hiker hunger would sometimes kick in when resupplying and resting in a town, especially after a couple weeks in. Downed a large pizza and salad between both of us no problem a few times.  Wasn’t uncommon to drink a cartoon of OJ between us within a couple of hours.

 

[Author]

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