2

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Intermittent Fasting and decreased performance

Answered on September 12, 2014
Created May 05, 2010 at 2:56 PM

Lately I've been seeing a significant decrease in performance during my IF days. My Crossfit WOTD times are higher and I just feel lethargic during my workouts. I'm fasting for no more than 16-20 hours two days a week. I eat 95% paleo, my only deviation coming from the dairy derivitaves found in my protein supplement. Has anyone else seen this happen to them? Can anyone give any insight or advice as to how to deal with the lethargy and decreased performance?

20172354416166004d612e7d6bdd2f5e

(352)

on May 31, 2010
at 03:21 PM

Yep. here ya go: http://www.ncbi.nlm.nih.gov/pubmed/19197210 Cheers!

7f9ec40efd2e7f6e5e5a68be7d135321

on May 12, 2010
at 01:21 AM

The metabolic benefits that come after about 12 to 14 hours of fasting isn't as significant as compared to overall calorie deficit that tends to result from IF. Don't let this stop you from doing IF.

B8d8d1a9d9da5c1fbc1344e4e06bf69a

(174)

on May 12, 2010
at 12:15 AM

additionally, I feel very socially cold and am stumbling on my words. This isn't uncommon for me, however. It just gets worse when fasting for 14+ hrs.

5de2fffda92c0bf2be7ede10cad55546

(1781)

on May 11, 2010
at 01:53 AM

Absolutely agree, it takes time to make the shift to burning ketones for fuel, but amazing difference when adapted. A lot of people give up before adapted. I've been VLC for 2 years and ZC now for 6 months and I can attest that physical performance absolutely improves out of sight.

64242a1130eb51f4852f78beed38b3d5

(1343)

on May 11, 2010
at 01:20 AM

Primal FTW!!!!!

65125edd5aafad39b3d5b3a8b4a36bb7

(6092)

on May 10, 2010
at 08:34 PM

Do you have a link for that study?

83d6a06c93bb3490dbca339cbbb63385

(526)

on May 07, 2010
at 01:33 AM

Exactly. I was going to say the same. Sounds like he needs some rest.

A231170e329756974c79cd8d2116351c

(103)

on May 06, 2010
at 05:26 PM

I personally get very cold at around the 13 hour mark, and my motor coordination gets worse.

5de2fffda92c0bf2be7ede10cad55546

(1781)

on May 06, 2010
at 01:27 AM

I have had the exact same type of experience. Two full days on a pick and shovel fully fasted, energy just never let up, everyone else took frequent breaks and ate lunch while I kept going effortlessly. Wonderful feeling.

4d40b7c7c84a3b6639e274ba548002ff

on May 05, 2010
at 11:45 PM

I hadn't thought about which specific WOD's I was struggling with but you are right about the strength WOD's suffering a more noticable decline. I'll tinker with my IF scheduling and diet a bit and see what I come up with. I also tend to be keep myself right on the cusp of overreaching/overtraining and find I have to reign myself in at times, which could be a factor also. Thanks for the great advice.

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7 Answers

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6
20172354416166004d612e7d6bdd2f5e

on May 05, 2010
at 04:45 PM

I've got a couple things to offer to this conversation: a wee bit of science, and some anecdotal evidence.

Last year a study published in the Journal of Strength and Conditioning Research concluded that in a group of cyclists who had just completed 3 weeks of caloric restriction and IFing:

There were no significant differences between baseline and post-CR for submaximal trial RER, power output, VO2, RMR, VO2max, or workload at VO2max. However, RPE was significantly lower, and PWR was significantly higher post-CR, whereas RER did not change. The cyclists' PWR and body composition improved significantly, and their overall weight, fat weight, and body fat percentage decreased. Lean mass was maintained. The cyclists' RPE decreased significantly during 2 hours of submaximal cycling post-CR, and there was no decrement in submaximal or maximal cycling performance after 3 weeks of CR combined with overnight fasting. Caloric restriction (up to 40% for 3 weeks) and exercising after fasting overnight can improve a cyclist's PWR without compromising endurance cycling performance.

Basically, the only value being measured here the actually "decreased" was RPE (rating of perceived exertion), which happens to be the only subjective measure which didn't actually affect performance.

Now perhaps we're not comparing apples to apples as this study was done on endurance cyclists, but they did test both aerobic and anaerobic measures ("submaximal" and "maximal"). This research suggests that caloric restriction with IF, in this case done by overnight fasting followed by exercise in the morning without eating, improves performance, and does so in a way which preserves lean mass and decreases body fat.

My own current experience with endurance training (Ironman coming up at the end of June) with HIIT done on my fasting days corroborates what I've read here. I've got a more steady flow of energy on long endurance days, and I'm much stronger when doing high intensity resistance training than previously.

"Paleo" diet suggests which groups of foods ought to be eaten/excluded, but diet composition may vary immensely. The single biggest factor for me in increasing my athletic performance has been increasing fat intake (mostly animal) to ~70% of calories, thus my body is becoming increasingly keto-adapted, and IF days happen spontaneously for me now.

For me, knowing that science has given us good evidence that IF doesn't cause things like low blood sugar (there are exceptions here), loss of muscle mass, slower metabolism etc. did a great deal for my own "buy-in" to it as a healthy practice. Now I'm amassing personal anecdotal evidence to keep me committed to this performance enhancing, fat loss causing, appropriate stress on my body.

Suggestions? Perhaps try messing with your diet composition, drink plenty of fluids while fasting, change frequency/length of fasts. Coffee before a workout helps me as well.

Hope this is helpful. Good luck.

Cheers!

65125edd5aafad39b3d5b3a8b4a36bb7

(6092)

on May 10, 2010
at 08:34 PM

Do you have a link for that study?

20172354416166004d612e7d6bdd2f5e

(352)

on May 31, 2010
at 03:21 PM

Yep. here ya go: http://www.ncbi.nlm.nih.gov/pubmed/19197210 Cheers!

4
703331bec3d551d21d2178f60c9963c1

on May 05, 2010
at 03:44 PM

Which type of WOD's are you seeing declines on? I'd imagine since you're IF'ing and eating nearly perfect paleo, then you're probably fueled by fat the majority of the time, especially during a fast. The non-aerobic systems simply don't run as well on fat, so it's my guess that your strength and strength endurance WODs are declining, like any heavy lift or something like Fran. On the other hand, I'd expect your longer met cons to have almost no drop in performance or possibly be gaining since the slow glycolytic run fine on fat. So the solution might be to IF around your longer met cons and then eat more regularly and maybe mix in some sweet potatoes pre and post when you're lifting heavy or sprinting.

There's also the fact that you're doing CrossFit (high intensity and volume) while also mixing in IF a few times a week, so you may not be getting enough food in general to support adequate recovery and could be overtraining, which will cause performance decreases across the board.

4d40b7c7c84a3b6639e274ba548002ff

on May 05, 2010
at 11:45 PM

I hadn't thought about which specific WOD's I was struggling with but you are right about the strength WOD's suffering a more noticable decline. I'll tinker with my IF scheduling and diet a bit and see what I come up with. I also tend to be keep myself right on the cusp of overreaching/overtraining and find I have to reign myself in at times, which could be a factor also. Thanks for the great advice.

3
7f9ec40efd2e7f6e5e5a68be7d135321

on May 09, 2010
at 06:40 PM

Working metabolism is variable and influenced by many things like psychology, sleep, illness, food intake, etc. Your performance, in part, reflects your current metabolism.

Unless your primary purpose is to bang out PRs with every session, why go through the trouble with scheduling your workouts with your eating patterns?

My suggestion is to keep it simple. Train in the current metabolic state. Do this enough time, and that metabolic state becomes adaptive and should improve. Your physical performance will be better regardless of prior energy intake.

After all, it is the basis of CrossFit -- anywhere, anytime. But beyond CrossFit, it's as Paleo as you can get.

Best, Johnny

PS. The metabolic shift from glycogen to ketone bodies as fuel may also be more efficient over time, if given the stimulus. Another thing to consider.

5de2fffda92c0bf2be7ede10cad55546

(1781)

on May 11, 2010
at 01:53 AM

Absolutely agree, it takes time to make the shift to burning ketones for fuel, but amazing difference when adapted. A lot of people give up before adapted. I've been VLC for 2 years and ZC now for 6 months and I can attest that physical performance absolutely improves out of sight.

3
699d8d5bb5d186c23c79aef4f7bf1145

on May 05, 2010
at 04:49 PM

I had the same experience as well. I have had better results by doing IF on my rest days. In addition to this I also have found the load of a standard 3/1 crossfit schedule too much to do when restricting calories. I suggest tinkering (a la Robb Wolf) with your training and diet until you find your own sweet spot. Despite what Glassman might assert, there is nothing magical about 3/1.

2
1c4ada15ca0635582c77dbd9b1317dbf

(2614)

on May 05, 2010
at 07:10 PM

I've had this once or twice before myself. I upped my fat intake a bit and took an extra rest day, and haven't felt the slump again since. Worth you trying a bit more fat I would say.

83d6a06c93bb3490dbca339cbbb63385

(526)

on May 07, 2010
at 01:33 AM

Exactly. I was going to say the same. Sounds like he needs some rest.

1
64242a1130eb51f4852f78beed38b3d5

(1343)

on May 05, 2010
at 03:21 PM

I can't speak all the science but I typically feel low to start and then it's like a rocket, on target and speeding up. I've been building a fence lately and one day we used a 2 man auger with a non paleo pal, he was having to stop every 5 minutes while I could easily have kept going. Very good even flow of energy all day.

5de2fffda92c0bf2be7ede10cad55546

(1781)

on May 06, 2010
at 01:27 AM

I have had the exact same type of experience. Two full days on a pick and shovel fully fasted, energy just never let up, everyone else took frequent breaks and ate lunch while I kept going effortlessly. Wonderful feeling.

64242a1130eb51f4852f78beed38b3d5

(1343)

on May 11, 2010
at 01:20 AM

Primal FTW!!!!!

0
B8d8d1a9d9da5c1fbc1344e4e06bf69a

(174)

on May 12, 2010
at 12:13 AM

I notice muscle loss when I fast for 18+hrs. Quite a bit actually. I've only been doing paleo for about a week, but I used to fast about three times a week for 16+ hrs each time, and I always noticed muscle loss. I know the studies say this isn't true, but I'm fairly certain it happens to me. Plus I can't do sprints worth shit. From now on, I might do 12 or so hrs (and I know, benefits don't really come until 16), but I'm probably not going much over that.

B8d8d1a9d9da5c1fbc1344e4e06bf69a

(174)

on May 12, 2010
at 12:15 AM

additionally, I feel very socially cold and am stumbling on my words. This isn't uncommon for me, however. It just gets worse when fasting for 14+ hrs.

7f9ec40efd2e7f6e5e5a68be7d135321

on May 12, 2010
at 01:21 AM

The metabolic benefits that come after about 12 to 14 hours of fasting isn't as significant as compared to overall calorie deficit that tends to result from IF. Don't let this stop you from doing IF.

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