Marks Daily Apple
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20 Dec

Monday Musings: Thoughts on Fasted Training

Even if I’m not expressly fasting, I gravitate towards working out on an empty-ish stomach. It just feels right to me to run on empty or, at the most, a couple eggs or a handful of nuts. Lifting heavy things while picturing the pounds of meat to come is, for lack of a better word, kinda Primal. The hunger fuels my performance – at least it seems to – while a brick of food sitting in my belly is a subjective burden. Look around the blogosphere (especially at Leangains and Free the Animal, where Martin Berkhan and Richard Nikoley have been doing some great work together charting Richard’s Leangains journey) and you’ll see that plenty of others are feeling the same.

What’s cool is that research in objective support of this stuff keeps coming. Earlier this week, the NY Times highlighted a Fall 2010 study that Martin broke down back in September. Both covered it quite extensively, and while I prefer Martin’s take on it, I also like that working out on an empty stomach is actually being recommended in a mainstream publication like the Times. They don’t even include the normal caveats from stuffy experts.

This particular study took lean, active young 20-something men and broke them up into three groups: a fasted training group, a fed training group, and a non-training control group. The fed and fasted groups ate the same meals made up of the same foods, just at different times relative to the workout. They both trained in the morning, a mix of hard endurance stuff, lots of glycolytic work. No weights. The fasted group destroyed the fed group. All groups were eating an isocaloric high-fat, high-carb (50/40/10 F/C/P) diet well above maintenance, but the fasted group gained the least weight and the least amount of body fat. Most importantly, glucose tolerance and insulin sensitivity improved in the fasted group and suffered in the fed group (you don’t even wanna know about the poor control group), meaning the fasted folks were better able to shuttle nutrients into their muscles and handle both carbs and fat together. I can’t imagine the food quality was doing them any favors, either; Martin notes that subjects were supplied with take home meals, which I read as processed, boxed crap full of frankenfats and refined grains.

There’s more, of course. A study released earlier this month describes the beneficial effect of fasted endurance training on post-workout eEF2 activity. eEF2, or elongation factor 2, is a crucial factor in muscle protein synthesis. eEF2 is subject to either dephosphorylation (generally good for protein synthesis) or phosphorylation (generally inhibitory of protein synthesis). Subjects were split into two groups: CHO, who received a carb-rich breakfast before and carb-rich drinks throughout an endurance training session; and a fasted group, who received only water. Training was 3x a week for 2-hours at 70% VO2 max for both groups (not my cup of tea, personally). The CHO and fasted groups both had comparable eEF2 phosphorylation pre workout, but post workout, CHO group phosphorylation doubled and dephosphorylation was largely negated, while fasted group dephosphorylation was maintained and phosphorylation remained stable. Remember: dephosphorylation good for muscle maintenance, phosphorylation not so good. As I’ve said before, this type of endurance training can be fairly catabolic, and I myself had trouble maintaining weight, let alone actual muscle mass, as a runner.

Another study seems a bit more mixed. It looked at sprinting athletes, either fed (24g whey protein, 4.8g leucine, 50g maltodextrin/glucose) or fasted and then told to sprint. Power output and performance were similar, but fed athletes displayed greater muscle protein synthesis and muscle cell signaling. From what I can tell, though, the fasted athletes were never fed, not even after the sprinting. This is definitely interesting, but I’d like to see what happens to fasted athletes who eat right after training. The study’s authors even conclude that the important thing is ingestion of carb/protein in “close proximity” to time of training irrespective of chronological order.

The takeaway? It’s just more fuel for the fire. Fasted training improves metabolic performance and helps maintain muscle after endurance exercise, and, as long as you eat soon after, can jibe with intense sprint work. I’ll continue covering this topic as new research is unveiled. Stay tuned.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Be warned though, once you go fasted, you can’t go back.

    Seriously though, going from fasted training to unfasted is difficult. It’s too enjoyable with the former.

    Ahmed wrote on December 21st, 2010
  2. If you have found success with intermittent fasting, then awesome – keep it up…but to suggest that it has been proven conclusively better than training in fed state (Or that anyone with a different point of view is an idiot), is extremely narrow-minded. I expect people on this site to be more open about things.

    If you are interested in hearing a different take on it (not just bashing it by the way), here’s a link. For those that don’t recognize the name, the dude is extremely well known in fitness circles,and cites all his sources.

    anzy wrote on December 21st, 2010
  3. Another article talking more about fasted cardio work (sprints included)…

    anzy wrote on December 21st, 2010
  4. Test

    Fit65 wrote on December 22nd, 2010
  5. Sorry about the previous, I’ve had a problem posting.

    The issue with high fat diets is that they have been shown to promote insensitivity of insulin receptors. Is it possible that training on empty eliminates this problem?

    fit65 wrote on December 22nd, 2010
  6. Excellent article. I’ve personally been practicing IF for about 3 years and don’t eat until about 7 or 8pm every day. I always train on an empty stomach and have some Vega protein and 85% dark chocolate afterward. Doing so I’ve lost 45lbs and kept it off. Now I compete in Kettlebell Sport.

    Bob Garon wrote on December 22nd, 2010
  7. Mark I have had my best workouts while training on a empty stomach. I have tried to workout on a semi-full stomach and it just doesn’t work for me.

    I have tried fasting…but that was something to behold!

    Patrick Kallie wrote on December 23rd, 2010
  8. I have a 3-hour martial arts class on Saturday mornings–really the only sustained workout I do during the week–and I do like to have a scrambled egg or a bit of bacon about an hour before. Usually coffee with cream, too, because I read a bit about athletes performing better with a little caffeine, and that seems to be the case with me.

    But eating toast with my breakfast will drag me down every time. Took me years to figure that out, because the habit was so ingrained.

    Holly wrote on December 23rd, 2010
    • Thanks Holly! You are the first I have met in the same position as me. I have martial arts every Sunday and our gradings usually include 3-hour intense physical workouts combined with the technical side of the grading. I have to have protein before the class as well, but I need enough time to digest it. I find that if I am still digesting it when I get there I tend to get very dizzy and/or pass out. The same if I fast. I have coconut cream in my coffee :)
      Grains are not good for me before a workout either.

      Kitty wrote on December 23rd, 2010
      • Our classes are only 1 1/2 hours normally but are still very intense. The gradings are well over 3 hours once past the second grading.

        Kitty wrote on December 23rd, 2010
  9. I like the idea of training fasted, but when I do Crossfit in the mornings on an empty stomach, I actually bonk and get dizzy. Maybe it is from not being fully paleo, and I’d do better if I was running on fat. But at this point, I’m still working on the 80/20 principle, so I eat a Lara bar about an hour before the workouts, and it seems to work for me. I do like the idea of doing a full fast once a week, however. Something to try for the new year.

    Julie wrote on December 30th, 2010
    • Hi Julie, have tried having just a good quality whey protein isolate before Crossfit in the morning, instead of a full breakfast? This might help get you past the dizziness etc.

      Kitty wrote on January 29th, 2011
  10. Sumo wrestlers do their workouts on an empty stomach.
    They are able to perform really intense training.
    Mind you, they are also able to put on lots of weight which is mostly fat.

    MDog wrote on February 11th, 2011
  11. Is it really safe to fast even if you are working out a lot? It might really be a suicide if that happens. I am not really a fan of fasting but I saw post stating about intermittent fasting and it is not actually a total fasting.

    Ernest @ weight loss drops wrote on April 12th, 2011
  12. I work out on nothing but a morning cup of joe. If I so much as take a bite of anything in the am, I’m bloated during my workout. It takes a little longer to warm up, but I love getting it done and having no distractions. Plus, Jack Lalane did it……..

    Dave wrote on April 8th, 2012
  13. Finally convinced myself to do it regularly, and I love it! Even back when I didn’t know better I was annoyed by people who kept saying everyone needed a bunch of carbs every hour for energy. Good to see other people who are living proof of the contrary. After all, our bodies must be much wiser than relying on a fresh supply of sugar all the time. Fasted training rocks!

    Reka wrote on July 16th, 2012
  14. Hi Mark,
    I’ve been doing some follow up reading, especially in regards to the last article mentioned. It seems to me that the adaptations seen in fasted training are very impressive, and are great for post workout translation and sustaining muscle growth in endurance work, but have detrimental effects in HIIT, due to compromised size of glycogen stores, and potentially their use. So…the question is, for a university oarsman such as I, who trains in the primal way, low low HR for long time, heavy weights, a few HIITs / week, but who races at maximal effort for ~5-7mins, which is the time frame I really want to perform in, is fasted training beneficial? Love the site, love primal.

    George wrote on November 24th, 2012
  15. I can train fasted easily, but only if I wake up early and train. If I am training at 9am then I feel like I gotta have a coffee with cream and a couple eggs :)

    Sarah wrote on March 11th, 2013
  16. I’ve recently read a book called “The Art and Science of Low-Carbohydrate Performance” by Stephen Phinney and Jeff Volek and they go into detail about nutritional ketosis. In which it takes your body 2-4 weeks to fully adapt on a low/no carb diet. But once you’re adapted your brain/muscles will run on ketones instead of glycogen providing them with virtually unlimited energy 40,000+ Kcal fat stores vs 2000 kcal glycogen stores.

    I theorize that fasting speeds up this process. I also read that the digestive system can take up to a third of the body’s energy, so if you’re fasted there’s more energy for other purposes.

    J. P. PAREJO wrote on May 9th, 2013

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