5

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Intermittent Fasting While in Ketosis as Beneficial?

Answered on September 12, 2014
Created December 13, 2012 at 6:46 PM

I am about 3 weeks into a ketogenic diet, following the framework outlined by Volek and Phinney in their books. They recommend that protein is a set amount based on your height and ideal body weight. For me this is around 90g per day minimum. Carb intake is minimized, and for me its less than 20g net carbs (Atkins calculation) per day. Based on this approach, the rest of my energy needs come from fat. If I am active, I eat more fat. The protein and carbs remain consistent as total amounts, not % based.

I have been monitoring blood ketones twice daily and have been in the recommended range for some time now. I may not be fully keto-adapted yet (as they say it can take 4-6 weeks), but I am definitely generating enough ketones to provide adequate fuel for my brain and other organs once my body does largely adapt.

On the 'Ask the Low Carb Experts' podcast a few months ago, Jimmy Moore had Dr. Phinney on the show. It was a long show with a ton of great info, but there was one thing that Phinney said that didn't make sense to me and he didn't really explain.

What he said was that fasting is a bad idea because one will lose lean mass when not eating for an extended period of time. He said skipping lunch might be OK, but he wouldn't recommend going longer than that. There was no real further explanation or discussion on the topic.

Since the context of this show was ketogenic diets, I am under the impression he was speaking of fasting while in ketosis. Alas, I could not tell if his statement was general or specific.

Many people here are familiar with the Lean Gains (18/6) and the Eat Stop Eat approaches, in which you have fasting windows of 18-24 hours, but never actually have an entire day where you do not eat (well for most people most of the time). There are many supposed benefits to this type of fasting, and working out while in the fasted state has proven to conserve and even increase lean muscle mass, not break it down for body fuel.

So what I am wondering is if there is any scientific literature/studies/evidence regarding intermittent fasting while also being in ketosis. Does being in ketosis somehow negate the positive benefits associated with IF, or was Dr. Phinney perhaps making statements unaware of these types of routines?

My thoughts are that if I eat the minimum amount of protein every day, even if I fast for a 24 hour window in between, I will still incur the same benefits as anyone else and will not suffer the loss of any LBM. Additionally, I think the risk of me losing LBM is actually less by being in ketosis, since my body now requires less glucose to function optimally.

If anyone is aware of any studies or research out that proves me right or wrong, I'd really appreciate you sharing. And if you agree or disagree, please let me know what you think and why.

0425dfe4b5f5a87181043a542f4d29f6

on December 16, 2012
at 08:20 PM

Perfect post Alan!

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 08:52 PM

Thanks for the detailed response and sharing your perspective. I have no idea what 7% body fat feels like, so I can't really relate to some of what you shared. However I think your case that keto is irrelevant when doing IF is spot on

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 06:48 PM

I agree that resistance training is critical but am holding off now while my body is in the adaptation phase. Within 2-3 weeks I will be starting up a routine again.

705e66484ed64fe8e188123de398413e

(1013)

on December 14, 2012
at 05:28 PM

I think not doing resistance work would be a mistake if you want to preserve LBM. McDonald addresses athletes in general not just bodybuilders. For me I am more interested in the macro question is: Is the benefit of long-term (nutritional) ketosis worth the possible metabolic slowdown and reduced training ability? Or is it better to use refeeds/CKD? Looking forward to seeing the blood ketone numbers when you're done.

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 04:47 PM

Thanks for the update. I am familiar with McDonald's book on the ketogenic diet as well, but find it more geared towards body builders (hence the higher protein). Volek and Phinney's works however are geared more toward the general public and specifically the overweight. Right now I am not doing resistance training until I get fully keto-adapted, which is another 1-3 weeks. Once I get there I will start introducing workouts again and will see how I fare and adjust from there. More protein may be necessary, and I will be monitoring blood ketones to see what effect that has on my levels.

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 12:04 AM

Justin I don't have definite plans, this is merely theoretical and based on what I heard Dr. Phinney say. While he is usually very science oriented, I found this one claim of his to be unsubstantiated, even Jimmy didn't seem to agree but instead of discuss moved things along. If I were going to take this on (which I may), I would fast 3x a week and workout at least 16 hours into the fast. Workout would be 45-1hr of resistance training, maybe some kettlebells, incline walking

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 12:01 AM

Thanks for the down vote anonymous

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 12:00 AM

I've done the Lyle McDonalds PSMF where the parameters were as I stated. It's a higher protein intake compared with the traditional PSMF but the rest is the same so I don't see where I am confused. Either way my diet is nowhere near PSMF. Ketosis may share similar physiological implications as fasting but being keto-adapted is not the same thing as being fasted. Please share resources that explain how ketosis mimics fasting. Yes you need LBM for AA and Glucose if you aren't getting them via diet, so double whammy. Have you read the art+science of low carb living?

76211ec5301087de2588cfe3d6bccba9

(1178)

on December 13, 2012
at 11:40 PM

a PSMF is exactly what it says it is: a total fast (fluids and supplements only), plus just enough (NOT HIGH) protein to maintain LBM. My understanding of what you wrote was that you would be fasting with adequate protein in a 24 hour window. I misunderstood and you are only IFing while in ketogenesis. This is beneficial too. I don't have an incomplete understanding of ketosis though. I have been knee deep in research on it because I am writing a paper on it.

705e66484ed64fe8e188123de398413e

(1013)

on December 13, 2012
at 11:35 PM

What are your plans for exercise? With the amount of thought you've put into this I'm curious why you haven't mentioned timing your eating in a post-workout window.

76211ec5301087de2588cfe3d6bccba9

(1178)

on December 13, 2012
at 11:35 PM

Hi, I think we are actually in agreement more than disagreement. I am not talking about the body utilizing LBM for fuel. I am saying that it will take LBM for amino acids even when you are ketogenic because you have to rebuild tissues with AA. I agree that when in ketosis the body will not need as much glycogen since it will utilize free fatty acids and ketone bodies for energy. Secondly, ketosis does mimic fasting and this is a big part of its history and discovery--please look it up. Thirdly, please also look up protein sparing modified fast, because you appear to be confused. ctd...

705e66484ed64fe8e188123de398413e

(1013)

on December 13, 2012
at 11:34 PM

He's talking about a PSMF + Fat which is not a PSMF.

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 13, 2012
at 10:47 PM

I fully intend to test it myself but if it was a fact that doing so would not be beneficial then I wouldn't consider it. Even though sometimes I have no desire to eat now because I am totally satiated. Thanks for your input

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4 Answers

3
Fba408128497343799ac28ffbce1d884

(175)

on December 14, 2012
at 08:41 PM

I have been IFing for about 3 years...on and off. I train on an empty stomach at 5am. Both bodybuilding and powerlifting schemes. I don't eat a single thing until 1pm. By which usually a double tortilla wrapped extra beans and rice burrito finds its way into me for 1500 calories. then i basically just snack all the way until dinner..which is at 9pm..for another big meal. Then bed. So I pretty much break every rule in the book and still somehow get in shape for contests. Which can only mean one thing...: the rules are garbage.

There are no studies investigating IF on keto that I know of. But if you're worried about LBM breakdown on a fasted regimen, dont. Overall macronutrient intake will rule your goals. Outside of eating just one ridiculously large meal (which I dont recommend) any other kind of eating schedule doesnt make any difference. 6 times vs 2 times vs 5 times vs 8 hours vs 16 hours. Whatever. I do IF because it's immensely convenient. I did it also because i was eating 6-8 small meals every day for 6 years before I discovered two important things.

  1. I could eat just KFC and still get down to 7% and ready for a show. That's keto...for 22 weeks straight.
  2. I could eat nothing but low fat ice cream sandwiches, pop tarts, and rice cake, and whey protein and come in just a little above 7% (probably because of the water, but close enough).

Whatever the claims are on IF, I know for a fact that I feel mentally and emotionally better and have better energy for my AM workout on an empty stomach. Rather than stuff myself at 430, then stuff myself again at 7Am then again at 11, 2, 5, 8....etc. Longevity is an absurd claim, as those studies would take 50+ years to confirm, and IF as a theory has only been around for a few. Energy levels? maybe. I dont see much of a change between 16 hours of feeding and 8 as long as I'm eating the same exact amount. I have read all the relevant human research and even some of the animal--although the latter is questionable in its efficacy. I would suggest, treating IF as more of a tool of convenience and freedom, instead of letting it restrict your food protocols EVEN MORE?! How is it that things that are intended to be simple become so complex in their use? Why is it that when we talk about weight loss these days, insulin must be brought up? Sigh. Don't go ranting....must stop myself.

Take it from a veteran of continued weight gain and loss as I do this on purpose every year..somtimes twice a year.

No. fasting and keto are not at all the same thing. I never want to be in keto again..as I think it's one of the most absurd things you could do to lose weight if your'e grossly overweight. It's even pretty absurd for competitive bodybuilders under 10% bodyfat as we tend to get really "flat" on it. So..honestly..maybe for the diabetics. But I know how you feel. When i can only eat 200g carbs a day, I feel like im on keto too.

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 08:52 PM

Thanks for the detailed response and sharing your perspective. I have no idea what 7% body fat feels like, so I can't really relate to some of what you shared. However I think your case that keto is irrelevant when doing IF is spot on

0425dfe4b5f5a87181043a542f4d29f6

on December 16, 2012
at 08:20 PM

Perfect post Alan!

1
2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 13, 2012
at 11:12 PM

This is in response to nursling since it would span several comment boxes:

I don't agree with some of your points here. Specifically that LBM is not interchangeable with glucose. The liver and most muscles store glycogen, which can be converted into glucose if your body needs it. If you are glucose dependent and not getting enough carbs (and protein), your liver depletes and then if necessary your body goes after your muscles. This does not happen in one day though.

However if you are keto-adapted your liver glycogen stores have little to nil. In this state your brain and other organs are using ketones for the majority of their fuel, which means that they require much less glucose. So if you are keto-adapted and you do not get enough protein/glucose that day, your body would look to glycogen stores for fuel but it wouldn't need as much as if you were fully glucose dependent.

Next, you say that ketosis mimics fasting. This is not true. Full ketogenic adaptation takes week of restricted carbohydrate intake, at least on initial attempts to switch the body's primarily energy source to ketones and away from glucose. Yes you may generate some ketones if you fast, but that does not make you keto-adapted nor does it mean your body is using those ketones efficiently or at all.

Last, this would not be a PSMF. That type of diet is extremely low in fat and carbs and very high in protein. A well formulated ketogenic diet is very low carb, adequate protein, and moderate to high fat. Too much protein will result in increased glucose levels due to gluconeogenesis. Additionally a PSMF diet does not actually involve fasting, but it does require extremely limited calories.

Additionally I think you missed the fact that I said I would be eating the recommended amount of protein per day. Here is an example

Monday, I wake up and have breakfast at 8 AM. My breakfast has 45g protein and 50g fat and 5g carbs. I have lunch at 1 PM which has the same macros. I do not eat until 1 PM the next day, where I then have 50g protein, 40g fat, 3g carbs. Then I have dinner with roughly similar macros again. So on both days I got the required minimum of 90g protein and ate enough to be completely satisfied. But, I did not eat anything for a 24 hour window between 1 PM Monday and 1 PM Tuesday.

I appreciate you taking the time to respond but I think your understanding of ketosis and fasting is incomplete.

76211ec5301087de2588cfe3d6bccba9

(1178)

on December 13, 2012
at 11:35 PM

Hi, I think we are actually in agreement more than disagreement. I am not talking about the body utilizing LBM for fuel. I am saying that it will take LBM for amino acids even when you are ketogenic because you have to rebuild tissues with AA. I agree that when in ketosis the body will not need as much glycogen since it will utilize free fatty acids and ketone bodies for energy. Secondly, ketosis does mimic fasting and this is a big part of its history and discovery--please look it up. Thirdly, please also look up protein sparing modified fast, because you appear to be confused. ctd...

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 12:00 AM

I've done the Lyle McDonalds PSMF where the parameters were as I stated. It's a higher protein intake compared with the traditional PSMF but the rest is the same so I don't see where I am confused. Either way my diet is nowhere near PSMF. Ketosis may share similar physiological implications as fasting but being keto-adapted is not the same thing as being fasted. Please share resources that explain how ketosis mimics fasting. Yes you need LBM for AA and Glucose if you aren't getting them via diet, so double whammy. Have you read the art+science of low carb living?

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 12:04 AM

Justin I don't have definite plans, this is merely theoretical and based on what I heard Dr. Phinney say. While he is usually very science oriented, I found this one claim of his to be unsubstantiated, even Jimmy didn't seem to agree but instead of discuss moved things along. If I were going to take this on (which I may), I would fast 3x a week and workout at least 16 hours into the fast. Workout would be 45-1hr of resistance training, maybe some kettlebells, incline walking

705e66484ed64fe8e188123de398413e

(1013)

on December 13, 2012
at 11:35 PM

What are your plans for exercise? With the amount of thought you've put into this I'm curious why you haven't mentioned timing your eating in a post-workout window.

76211ec5301087de2588cfe3d6bccba9

(1178)

on December 13, 2012
at 11:40 PM

a PSMF is exactly what it says it is: a total fast (fluids and supplements only), plus just enough (NOT HIGH) protein to maintain LBM. My understanding of what you wrote was that you would be fasting with adequate protein in a 24 hour window. I misunderstood and you are only IFing while in ketogenesis. This is beneficial too. I don't have an incomplete understanding of ketosis though. I have been knee deep in research on it because I am writing a paper on it.

1
705e66484ed64fe8e188123de398413e

on December 13, 2012
at 09:12 PM

It seems unlikely that this kind of study has been done. So I would recommend testing it out yourself!

I agree with you. Choose the fasting window that gives you the most convenience, least hunger, and best total weight loss. Also you might try "extending" a shorter fast by making the first meal or two fat-only. If this has the effect of bunching your protein up into one or two late-day meals (ideally PWO) then this may be even better.

Personally I spent a lot of time worrying about maintaining LBM and I think it mostly impeded my ability to lose weight. After finally getting some respectable body composition testing, I realized that I didn't even have enough LBM to be worried about it anyways.

Edit: I am skimming Lyle McDonald's "The Ketogenic Diet" now. He does say the goal of Ketosis is to mimic fasting, which you and nursling have debated.

He also says at least some of the glucose your body generates is generated by breaking down protein - dietary protein if it exists else muscle protein. The most important aspect of eating the protein is to prevent muscle breakdown.

Regarding timing, he suggests 30-40 grams post workout. Also he says too much protein at one meal might disrupt Ketosis.

He also suggests much higher protein per day than Phinney, 180g/day for a 200lbs man.

Otherwise, not much here to answer your question so far.

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 13, 2012
at 10:47 PM

I fully intend to test it myself but if it was a fact that doing so would not be beneficial then I wouldn't consider it. Even though sometimes I have no desire to eat now because I am totally satiated. Thanks for your input

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 04:47 PM

Thanks for the update. I am familiar with McDonald's book on the ketogenic diet as well, but find it more geared towards body builders (hence the higher protein). Volek and Phinney's works however are geared more toward the general public and specifically the overweight. Right now I am not doing resistance training until I get fully keto-adapted, which is another 1-3 weeks. Once I get there I will start introducing workouts again and will see how I fare and adjust from there. More protein may be necessary, and I will be monitoring blood ketones to see what effect that has on my levels.

705e66484ed64fe8e188123de398413e

(1013)

on December 14, 2012
at 05:28 PM

I think not doing resistance work would be a mistake if you want to preserve LBM. McDonald addresses athletes in general not just bodybuilders. For me I am more interested in the macro question is: Is the benefit of long-term (nutritional) ketosis worth the possible metabolic slowdown and reduced training ability? Or is it better to use refeeds/CKD? Looking forward to seeing the blood ketone numbers when you're done.

2e3477a85563d4b7159814d5f4ea57d3

(435)

on December 14, 2012
at 06:48 PM

I agree that resistance training is critical but am holding off now while my body is in the adaptation phase. Within 2-3 weeks I will be starting up a routine again.

0
76211ec5301087de2588cfe3d6bccba9

(1178)

on December 13, 2012
at 10:45 PM

You will lose some lean body mass if you do a full fast without any protein intake, even while in ketosis. It is just because the amino acids your body always needs have to come from somewhere, and if you don't supply them exogeneously via protein intake, your body will break down LBM to get them. I don't see how being in ketosis would make you less likely to lose LBM when fasting, since LBM is not interchangeable with glucose.
Fasting is beneficial for a number of reasons, many of which are achieved by being in ketosis, since it mimics fasting. One benefit you will achieve from full fasting is the rest it allows your digestive system. Obviously if you are in ketosis or doing a protein-sparing modified fast (wherein you only consume the minimum protein requirements and nothing else), then your digestive system is still at work to a degree.
What it sounds like you are proposing is a protein-sparing modified fast. Eating once or twice a day with long stretches in between after keto-adapting is a great way to give your body a long time to rest, reap the benefits of fasting, and put less stress on your body by remaining in ketosis.


but that's all just my opinion

705e66484ed64fe8e188123de398413e

(1013)

on December 13, 2012
at 11:34 PM

He's talking about a PSMF + Fat which is not a PSMF.

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