Fat Adaptation Literature?

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  • #10223

    Hi there,

    I was wondering if you could supply the literature that drives the thinking behind fat adaptation. From what I’ve been reading on this site, it seems that it’s suggested that to encourage fat adaptation, eating a ratio of (fat:protein:carbs) 50%:25%:25% in combination with including a gradual increase of fasted zone 1/2 workouts will encourage this fat metabolism.

    I’ve been struggling to find any literature that supports this, and any studies that I find (including the ones cited at the bottom of the “Burn Fat to Go Fast” blog post) are studying ketogenic diets, with a macro spread of 70%:20%:10% (fat:protein:carb) (Including the FASTER study, cited in the blog post).

    I’m definitely unfamiliar with the design and process of ketogenic diets, but from my understanding from the reading in TftNA book and from the forum and blog posts on this subject, you’re not advocating for a full ketogenic diet (which I definitely agree with! The last thing I’d want is to get sick from a Clif Bar that shoves me out of ketosis on the hill). From my limited understanding, you’re advocating for a sort of “flirtation” with ketosis, that causes the body to utilize a larger percentage of fat at lower HRs.

    Is this supported by scientific literature and peer-review? Or is this something that is driven by anecdotal evidence that science hasn’t proven yet?

    I found this recent study reinforcing the HCO diet in endurance athletes as well: https://www.ncbi.nlm.nih.gov/m/pubmed/26061831/
    Of course, it’s talking about ultramarathoners who aren’t at the altitudes we operate at, but the metabolic mechanisms should be similar, no?

    In the “Rethinking the role of fat oxidation”, cited at the bottom of the “Burn Fat to Go Fast” Blog post, it seems to be describing a fat adaptation brought on by exercise alone (comparing Well trained athletes to recreationally trained athletes who eat a 30%:10-15%:55-60% diet (fat:protein:carb).

    As an addendum, I’ve started experimenting with shifting my Macros to a fat-dominant diet (50:25:25; fat:protein:carb) and have noticed my satiety has improved greatly. Is the goal of this diet to improve satiety while the exercise is the active ingredient doing the fat adaptation? Or to improve satiety to the point where I have a greater caloric deficit, the lack of carbs associated with that deficit driving the fat adaptation?

    It seems that most of these studies don’t take into account altitude as well, so if you could just point me in the right direction to your evidence, or clarify my points of confusion, it would be greatly appreciated!

    And thanks again for all of the information in the book and training plans! I’m feeling stronger than ever before!

Posted In: Nutrition

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    Anonymous on #10232

    There is so much literature on fat adaptation I am not sure where to start but here are some studies list lower down that you might want to look at. Many studies involving shifting macro nutrient proportions are conducted on obese and sedentary subjects so don’t really cross over well to what we do.

    I would say that our position comes, first of all, from empirical evidence gathered over 30 some years of training and coaching. Then from reading the scientific literature to see if what we have observed can be explained with science. This allows us to place a theoretical basis to our practical observations and connect some of the dots a bit better.

    For what we advocate we can can’t and don’t separate dietary manipulation from the exercise. We see them as working synergistically. Ketogenic diets work to increase you body’s ability to utilize fat for fuel at all intensities. There are many studies and a huge amount of anecdotal evidence to support this. The problem with ketogenic diets is that they can be hard to stick to. Tat’s why we recommend a diet with lowered carbohydrate content than the traditional USDA food pyramid but not take to the extreme of ketogenic levels. This will be easier to live with and will still result in good fat adaptation when coupled with a high volume of low to moderate intensity aerobic work. Including fasted AM workouts seems to enhance the fat adaptation process.

    My observations suggest that the higher the volume of training the athlete is doing the less he/she needs to restrict carbs to get a fat adaptation effect. Folks doing Z1-2 aerobic training for 8-10 hours/week may need to restrict carbs more to get a similar effect to someone doing 15+ hours of Z1-2 per week. One of the pros I coach is a vegetarian and eats a high carb diet but frequently trains 20 hours a week and does many fasted workouts. He seems to be very well fat adapted and can go for many hours in the mountains with no food and no drop in energy or performance.

    For decades the nutrition experts told us that fat maxed out at about 60% of maxVO2 or close to ones anaerobic threshold. This falsehood persisted up until recently by bing passed down from one generation of sport scientists and nutritionist/dietitians to the next. It was codified in text books and taken as gospel. Coaches cold see that this could not possibly be true but all the peer reviewed studies showed so the science was settled. Recent studies have completely debunked this dogma and verified what the old coaches knew. Why: All the old studies were done on untrained subjects. Volek’s F.A.S.T.E.R. and Seiler’s studies (below) used well trained endurance athletes the results showed that fat can be used at high rates right up to maximal intensity and rates twice as high as previously thought. One of my XC skiers was once tested in a lab and found to be getting 10% of his energy from fat when operating at his maxVO2. The lab folks told him that he had a messed up metabolism and needed to fix it. We had worked hard to get him this way so we ignored their recommendation.
    When Steve, Mark Twight and Scott Backes climbed the Slovak direct on Denali in 60 hours consuming only a few GU packets each, Steve was accused of lying about this by a dietitian. She told him it was physically impossible to do such a feat without taking in more calories. She had learned the dogma I referred to above and didn’t know about fat adaptation.

    The scientists do not always have all the answers.

    As for satiety question: Fat seems to make us feel more full for longer so we feel less hungry. I do not advocate caloric restriction for training athletes. You need calories to fuel your work. As mentioned above, I believe it is the combination of high volume work and restricted carbs that give s the best fat adaptation effect.

    Fat Adaptation References

    Study of 20 endurance trained 11 on HC and 9 on LC/HF diet for 12 weeks doing the same training. LC/HF body fat dropped 5.2% vs .7% for HC group. 100km time trial improved 4min in the LC/HF group vs 1 min in the HC group. Fat oxidation (use as fuel increased dramatically) during the 100km time trial LC/HF group vs the HC group.

    Jeff Volek’s F.A.S.T.E.R. study of 20 elite ultra runners. Showing that fat oxidation rates during submax intensity exercise by well fat adapted elite ultra runners was 2.3 time higher than those with a high carb diet.

    The Emerging Science on Fat Adaptation

    For those who struggle to pick out the important points of peer reviewed science studies. A summary of the findings of the Volek F.A.S.T.E.R. study with easy to read graphics and explanations.

    Study on high intensity interval protocol comparing well trained and fat adapted athletes vs recreationally trained athletes showed a much greater fat use at high intensity among the fat adapted athletes.

    This study shows the vast increase in fat oxidation (use as fuel) in fat adapted athletes and how this spares glycogen.

    jwaxman14 on #10234

    Thanks for the reply Scott! I think I’m beginning to understand the method you’re laying out.
    I’ll read through the literature you supplied. Sounds like the literature is working slowly from the ends of the spectrum in towards where you’re advocating. I’ll read through the rest! Thanks for the supply!

    Just to make sure I’m understanding this correctly: The fat adaptation process sounds like it’s operating on a spectrum, with exercise on one end and fat intake/carb restriction on the other. Depending on how much training you do (and your BMR, genes, etc.), the amount you need to shift your macros towards a ketogenic diet may be more or less, with more training necessitating less of a macro shift than a sedentary subject.

    I have a few follow-up questions as well:

    1. Should I be altering my carb/fat intake to correspond to the type of training I’m doing from day to day? i.e., if I’m doing strength or any high-intensity training on one day, increase the carbs and decrease the fat; while on the next, maintaining a high-fat ratio for Z1/2 activities? How consistent should this be?

    2. I’ve been tinkering with the macro shift to a more fatty diet for about a week and a half now (~50f:25c:25p) on a ~3000 calorie diet, working around 15-20 hours of week of training. This works out to still taking in around 250carbs a day. I’ve been trying to isolate 200 of those carbs to after my workout, and relying on a much more fatty diet before workouts (it actually probably works out to a 70f:20p:10c diet before my workouts, so a more classically ketogenic diet, followed by a workout and a carb bomb). Is this the right method? Will this be more conducive to fat adaptation if I spread the carbs out more? I’m trying to use the glycogen repair window to spur fat adaptation a bit quicker to make the carbs “count” less. Does this make any sense? Or am I just over-hypothesizing?

    3. I was reading elsewhere on this forum about losing your fat adaptation; I believe the answer on there was that you could lose your fat adaptation via diet, but that (I want to say Steve answered this) you could gain it back with a few fasted runs. Does this fat adaptation work like ketosis in that you can lose it quickly by acting contrary to how you got the fat adaptation? Does this operate on the same exercise and nutrition spectrum as gaining the fat adaptation? (i.e., can you drop out of the fat adaptation either if you lower the amount of fasted workouts while also not increasing your fat intake; or by adding a lot of carbs for a few days without compensating with more training hours?) How sensitive is the state of fat adaptation?

    4. Is there a good way to monitor this process? Is lab testing the only way to go?

    5. I’ve also noticed a peripheral effect that I wanted to ask you whether this was due to fat adaptation, or a lower carb intake, or just me connecting two dots not meant to be connected: When I was on an HC diet I noticed my weight fluctuate a huge amount, sometimes as much as 5-7 pounds a day (with a downward trend of about a pound a week). I expected that and wrote it off to water loss/gain. Now that I’ve moved my macros more towards a fat dominated diet (50:25:25), my weight isn’t fluctuating almost at all. It’s almost shocking, but I’ve had a very steady .2lbs a day drop; with a corresponding drop in fat mass and a gain in muscle/water mass. Is this something I should attribute to the high-fat diet? or is this just me stabilizing my weight loss and it’s a coincidence that it occured at the same time as my diet switch. I hypothesized that fat, being more water-phobic of a material than carbohydrates, may be stabilizing my water content? Am I overthinking this?

    Sorry for the pester! I just really want to understand what the theory is! Very interesting stuff!

    Thanks again,

    tomasaiduk on #10262

    Considering point 4. maybe this could answer your question? https://www.trainingpeaks.com/blog/the-peter-attia-approach-to-dieting-for-endurance-athletes-part-2/

    You can wear a continuous-blood-glucose monitor to measure glucose levels (which should be directly proportional to insulin if you are not diabetic?) and based on that track your fat oxidation. If you are at the baseline levels of blood glucose during an exercise it means that your body is oxidizing fat instead. However, they seem to be incredibly expensive, but Interesting article nonetheless.

    jwaxman14 on #10315

    Thanks Tom, agreed on the article! I’ll probably hold off going full-glucose monitor for now, but I’m really loving Peter Attia’s website! Thanks for pointing him out. He seems to have the most straightforward answers about where the knowledge terrain is sitting in relation to the threshold between anecdotal information and researched information, and the reliability of both. (https://peterattiamd.com/start-here/)

    I wanted to point out this interesting study that I found fascinating:

    I thought anyone interested in Fat Adaptation and endurance performance would find it interesting; of particular interest to me was that the mice in the study showed significant mitochondrial growth after 3 weeks of exposure to a ketogenic diet.

    chelski on #10375

    Hi Scott and all, I wanted to jump onto this and ask if you have any thoughts about how this applies to female athletes? The literature cited uses exclusively male study subjects (a common problem in both health/medicine and sports science…. I am sure there are relevant studies out there but they are fewer). As Stacy Sims famously says, “women are not small men.” There are reasons that is metabolically really a benefit in terms of endurance challenges, but it also might mean that the ideal macro ratios for us are different and our fueling strategies during exercise might be too. Do you have any observations/experience that would either suggest that your approach described above is equally appropriate for women, or that we should modify it in one direction or another?

    Aaron on #10397

    I’ve been enjoying listening to the podcast science of ultra to augment TFTNA.

    Episode 19 https://www.scienceofultra.com/podcasts/19 is is dedicated to fat adaptation for endurance athletes although if I recall focuses more on dietary (low carv, high fat) than training for fat substrate utilization.

    mountain_stoke on #10405

    Yeah, the Science of Ultra podcast is amazing. +1 on that.

    Anonymous on #10483


    I’m not able to cite studies on women and fat adaptation because I do not know of any. However, I’ll hypothesize that this is likely to be an area where the distinctions between men and women athletes is rather small. I say this because we are talking about the most basic metabolic processes that are common across virtually all higher mammals. These are the processes that govern mammalian life itself. Even though there is a dearth of studies on the gender differences in human endurance metabolism there are literally thousands of studies on endurance in mammals. None of the many dozen’s of studies I have read on this subject over the years has ever mentioned any differences in male/female metabolic responses to training. No mention is ever made as to the sex of the rodents or dogs or horses in these tests.

    My personal experience with training women endurance athletes is that they respond identically to men and can handle the same training loads as men at their same relative training level. I have worked with a number of women who have used the same fat adaptation strategies as men with good success and no ill effects.

    I would be very interested to hear of any studies showing differences between men and women for any and all endurance training adaptations.

    I hope this helps,

    chelski on #10532

    Thanks very much for the reply, Scott. Hearing that in your work with both men and women the fat adaptation intervention works and is beneficial is very reassuring. Thanks so much for sharing your wisdom with us so we can learn.

    And Aaron and mountain_stoke, thanks for the podcast reference, I just listened to an episode and it was great. Definitely will tear through them.

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