If it ain’t broken…

Intermittently-fasted Lambo

Let’s say your rich uncle dies and leaves you his Gallardo. On your first track-day you get spanked. To make matters worse it’s by guys in cars half the price. They are laughing. Do you get out your spanners and start fiddling with stuff in the hope this will make it faster, or do you learn how to use what you are given?

Same logic doesn’t seem to apply with dieting. Have a look at the following comment:

“Hey, so I’m going to lengthen my fasting window and add in a couple of 24-hour fasts and go all paleo for my carbs. Do you think this is a good idea?”

Is this person looking to experiment with the method out of curiosity to compare results with the ones that have already had, or are such ideas spawned out of frustration with their own lack of results and nutritional understanding? Having patience is not as fun as thinking up wild ideas of course.

Sometimes you may need to deviate from the standard plan. If you’re going to do that though, then you need to have a little wider understanding.

“Can I lengthen my fasting window?” “Can I do fasted training without BCAAs? I’ve heard they spike insulin and are bad for the fast.” Two consistently reoccurring questions. A few points need to be considered.

Can I lengthen my fasting window?

Should you? I mean what is the reason you wish to do so?

Is it because you think it will give better results?

Highly doubtful it will. Recall the hierarchy of nutritional importance. Overall energy intake for the day and then your macros (specific macro-nutritional intake) are far more important than timing. Stop looking for a shortcut. Putting two 24 hour fasts a week on top could well do more damage than good (explanation below).

Is it because you have to do it one day as you haven’t got time for lunch?

Sure, then do it. On the odd occasion, this is not a problem. As long as you keep your feeding times regular 90% of the time then you won’t upset your hormonal pattern and won’t get hungry during the fast. (Leaner guys, see warnings below.)

Is it because you have to have a shorter feeding window for scheduling reasons?

In which case it’s fine, but again keep things regular. If pushed for a figure then I’d say shorten it to a minimum of 5 hours. Less than this and you run into problems. I’d prefer to have a 10-hour feeding window than a 4 hour one. (More help on setting your feeding window with irregular work patterns here.)

Ok, why the 5-10 hour thing? What are the problems?

Firstly, trying to fit all your food into a 4 hour period or less can be tough, even when cutting, almost impossible when bulking. To do it you’ll have to resort to shitty food choices that will be micro-nutritionally poor and won’t keep you very full for long. Even if you are cutting and feel that hunger isn’t an issue, don’t forget – you won’t be cutting forever. Set things up from the start in a way you can continue in the long run.

Secondly, longer fasts lead to a greater likelihood of muscle catabolism (muscle loss). Consider the situation where you’re well into your fast:

      1. The body can use your fat stores or your muscle for energy.
      2. It will break down both fat and muscle into FFAs and amino acids respectively, to be whisked away in the blood stream to fuel different parts of the body.
      3. The body burns fuels in the ratio they are available.

Re-read the third point. For this reason, the risk of muscle loss when fasting is greater in leaner people. So what’s the fasting limit before it’s detrimental? Good question. I would love there to be a controlled, double-blind, clinical study of the chronic effects of fasting for different time periods on subjects with different body-fat levels in experienced weight-trainees to find out the limit, but this simply doesn’t exist and isn’t likely to ever happen.

What we do have though is evidence (consistent results) that people can have a 16-hour fasting window, losing little to no muscle while cutting down to shreds. We also have one case where a morbidly obese person was fasted by their doctors for over a year without losing significant lean body mass.

Practically, if you’re heading under 10% I certainly wouldn’t push the fasting time past the 16-hour mark on a regular basis. Over 10% you have more leeway -the degree to which is unknown.

Can I do fasted training without the BCAAs?

If* you are going to do fasted training and can afford to take BCAAs then take them. While it is true that BCAAs do cause a slight insulin spike, the negatives of this are likely far outweighed by the potential for muscle catabolism if they are not taken. If BCAAs are too expensive then take 25-30g of whey. Yes, I know there are conflicting view points out there (don’t bother posting them in the comments, it will only confuse people) and yes, I have read them. I’m no supplement company fan. Still, this is one area where I would err on the side of caution. Martin Berkhan explains this well here.

*Bear in mind that Leangains doesn’t have to be done with fasted training. Some people seem to be confused about that. Though there are some interesting studies on the acute effects, it is not proven that fasted training is superior to fed training over the long term, or the other way around (as far as I know). Choose whatever training time fits your schedule best. I can’t say I have observed a significant difference between fed and fasted training client groups. Martin will know better.

I’m not against experimentation, but if you don’t have to then don’t try to fix something that isn’t broken. Succeed first and then play around.

It’s easy to procrastinate and kid yourself that you need to understand all the science and minutiae before getting started. That rabbit hole goes deep though. Procrastinate for too long and you’re dead…

Sunday morning. Beautiful sunny day. Your uncle’s car keys drop into your lap. Are you going to go out and buy a book on car mechanics?

Thank you for reading.

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About the Author

Andy Morgan

Hi, I'm Andy, co-author of 'The Muscle and Strength Pyramid' textbooks and founder of RippedBody.com. This site is my sincere effort to build the best nutrition and training guides on the internet. Some readers hire me to coach them, which I've been doing full-time, online, for the last seven years. If you're interested in individualized, one-on-one coaching to help you crush your physique goals, let's start the conversation. (You can read more detailed bio here.)


  1. […] will threaten adherence by making your diet more complicated and restrictive. Refer to the ‘if it ain’t broken…‘ […]

  2. David Whitney says:

    Would ingesting some fat, like coconut oil with the bcaa’s or whey help to keep our bodies from converting any of the aminos into glucose? I would deduct the fat from my daily calories.

    1. Andy Morgan says:

      I.e.: Would the ingestion of fat blunt glucose response? No. But more importantly, you’re worrying about a problem where there isn’t one David.

  3. Maciej says:

    Hi Andy,
    I was doing CKD for some time and now added IF 16/8 to that. I was always doing fed training in the afternoon but as I now have only 8 hours window to eat I’d prefer to do Big 3 Routine in the morning. I have BCAAs with glutamine which have 2g of carbs in a serving. I’d have to have 3 servings before my first meal. I know your article clearly says to take BCAAs but is it still valid when I’m doing keto? I have to add I’m in a cut right now. Thanks!

    1. Andy Morgan says:

      Yes. Here’s my thinking: The advice concerning BCAAs is independent of whether you’re fat adapted or not. The question then becomes whether the BCAAs will bring you out of ketosis to a significant degree. Given the quantity of BCAAs is small, though they’ll spike insulin (I believe), I don’t think it’ll be in any sustained way that will make a difference.

      Thanks for the question Maciej.

  4. […] Evite divisões extremas de macronutrientes, opções como somente gorduras e proteínas no começo do dia e somente carboidratos e proteínas mais tarde. – esse tipo de coisa não traz benefício algum e irá prejudicar a adesão a dieta por torná-la muito restritiva e menos saciante. Veja a regra “se não está quebrado…“. […]

  5. […] rates of progress, for the person that follows the advice on this site ‘to a T’ (instead of tweaking things). I’m not going to talk about the best possible outcomes I have seen, nor what can be […]

  6. asai says:

    I got a question Andy, what should the calorie split be for rest days? Right now my feeding window is from 10AM-6PM and I am also doing the low carb/high fat since it is rest day. Should I eat most of my carbs at night so that way I feel more full then? I also train in the morning usually at 5AM

      1. Joey says:

        Andy, I really admire your patience.

  7. Hey Andy , I have a problem here !! . I just got excepted in a new job lately and everything concerned with the eating window was messed up . Basically , because of my job rules , I`m not allowed to eat. So the only way I can beak my fast is when I get back home which is only 5 minutes away from work . In that case , I would have fasted for 18 hours .You have stated that longer fasting may cause muscle loss. So I`m afraid that I might lose some muscles here since I`m quite lean (9% body fat) . Do you recommend sipping a 10g BCAA when I reach 16 hours of fasting or 18 hours is ok ?? what do u suggest ??

    1. Andy Morgan says:

      In which case, shorten your feeding window to 6 hours Tariq, doesn’t have to be a big deal, not a massive change.

  8. […] will threaten adherence by becoming very restrictive as well as less satiating. Refer to the ‘if it ain’t broken…‘ […]

  9. […] Keep to the plan. – It works! Don’t make the classic mistake of trying to fix something that isn’t broken. […]

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