T Nation

Pre-Workout & Intermittent Fasting?


I agree 100% with the benefits of fasting. I am suggesting the following 4 points:

  1. It is not better for most goals to train within the fasted period than to train during the fed period. My premise is that there may be benefits to fasted, low rep strength training with light active recovery for body comp, but that training in the fasted period doesn’t enhance the cell ageing effects of the fast over training in the fed period given that daily calories and fasting period are the same. Training itself promotes autophagy and improved insulin sensitivity and training in the fed period while having a separate fasted period is probably as good or better because of non-insulin mediated glucose uptake during training and because it can improve training work capacity.

  2. For overall health and probably for cell aging, intermittent fasting may better if done 2 out of 7 days or at most every other day. A 4-6 hour feeding window 2 out of 7 or every other day at most will activate the immune system to scavenge for degenerate proteins which also will lead to autophagy of precancerous cells. I think that when you IF every single day, it can desensitize the immune response or back up disposal pathways or use up resources needed to have a healthy immune system.

  3. The OP is in around a 1000 calorie per day deficit already. I don’t think that training during a fasting period is going to add much in terms of insulin sensitivity and improvements in cell ageing and body comp when you already have a 1000 calorie deficit. A 1000 calorie deficit is going to rapidly improve insulin sensitivity and is going to activate autophagy intermittently throughout the day. If you are already cutting 1000 calories a day and training, then the length of your fasting periods and whether you train in the fasting period don’t seem to matter to me.

  4. I.F. on top of a constant ketogenic diet where the dieter is fully adapted to burn fat and ketones as the 2 primary fuel sources is not going to further combat cell ageing. A ketogenic diet already deprives cancerous cells of glucose, and reduces the body’s need for gluconeogenesis since ketones are being made around the clock by the liver. In ketosis, I doubt that the body even senses a difference between the fasted and fed state. If you don’t eat breakfast, the liver doesn’t say “hey, we need to catabolize some protein to make glucose”, it says " make more ketones". I am suggesting that at a given caloric intake, IF, and particularly, fasted training on a constant ketogenic diet does not make sense. It may not be bad, but it doesn’t make sense that it would enhance the benefits of the ketogenic diet.

Short summary: IF and particularly fasted training, for someone already on a 1000 calorie deficit, or already in constant ketosis seems unlikely to be better for any purpose.


The only issue with this premise is that it presupposes that being in a ketogenic state via dietary intake equates to ‘being fasted’. This is clearly wrong. As you know, even in a fat-adapted person, eating modest protein will still result in an element of gluconeogenesis. Further, even a well-formed (organic, grass-fed, optimum fat macros, etc) ketogenic diet will result in some inflammation, e.g. detected through liver production of c-reactive protein. Fasting, however, will not. Finally, as per my initial assumption, caloric restriction is MORE likely to result in loss of lean mass through protein turnover as research suggests this is five times lower during fasting. For all of the above, fasting to maximise autophagy is superior to alternative modes.


Not quite. I am saying that adapted ketosis the body doesn’t get into truly fasted state because blood lipids and ketone levels from fat produce a near constant, stable level of energetic substances from liberated fat even during long periods without eating, so it is not possible to send a “fasting” signal to the liver that will turn up autophagy when keto-adapted.


I’m lost. When you are fasted; you are fasted. Your body doesn’t remember you are keto-adapted after 5 days without food: liver glycogen is depleted and autophagy is amplified. It’s that simple, really.


I don’t agree. The liver is running on ketones and fatty acids at that point because liver glycogen is minimal. You have enough fat to fuel the liver for months and it stops making glycolytic enzymes almost altogether. That’s why someone coming off of a very low carb diet can get 200+ blood sugars on a glucose tolerance test because the liver (and muscles) don’t even have enzymes to burn glucose at that point. Insulin tells the liver and other cells to make glycolytic enzymes and when insulin is chronically low, glycolytic enzyme levels in cells drops to nearly nil. It takes up to a week of eating 150+ grams of carbs to pass a glucose tolerance test coming out of ketosis.

Being “unfed” in extended ketosis is fundamentally different for the liver that a “fasted” state where the body still wants to run on carbs.

Autophagy only cranks up for a short time during a fast because after 24 hours it’s much less expensive to make ketones than generate glucose from body tissues. You have to eat enough carbs between fast periods to turn back on normal glucose burning mechanisms.

Ketosis is the liver’s way of getting OUT of a glucose dependent “fasted” state that activates autophagy.


You are not quite right there. There are ample cases of obese people losing their remaining skinfolds through fasting. Such a process would not be viable without a large degree of autophagy.


When you are fasted you increase noradrenaline production, which will also lead to a higher adrenaline level. This will help with strength work and cardio. And you would think that it would help with Crossfit too, BUT Crossfit is, by itself, very “adrenalin-producing” so you can put yourself in a state of excessive sympathetic activation which can create anxiety, refusal to do work and afterwards it can lead to CNS fatigue by keeping the CNS amped up for too long. This will either be due to a desensiization of the adrenergic receptors (because they were overstimulated) or dopamine depletion (because you make adrenaline from dopamine, so if you produce too much you can deplete dopamine and you will feel like crap).


I said that fasting causes autophagy. I’m saying that in nutritional ketosis, the autophagy from fasting is blunted by the switch over to a ketone metabolism.

Fasting produces more autophagy when the body is has not downregulated glucose as a fuel source which it does during ketosis, and also during prolonged carb fasts. That is why I.F. is likely to be better if done only 2-4 days a week so that glucose metabolism stays high and the body needs to turn to things like old skin proteins for glucose.


OK, we are at cross purposes here. My concluding remarks: fasting is fasting, ie, absence of ALL macros. Talk of a glucose fast or keto fast is meaningless. The advantage of the latter is that you can trigger autophagy sooner, and arguably with less side effects, than the former. Otherwise, both will still lead to the same destination: ketosis and autophagy.


Closing statement: Subjects in full nutritional ketosis have been found to function safely even when blood sugar levels were supressed to LESS THAN 10 mg/dl through administration of exogenous insulin! Glucose is not needed in full adapted ketosis. People will still tend to maintain low levels of blood glucose (circa 60) in full ketosis because there are tiny amounts of autophagy plus dietary protein fueling gluconeogenesis at that point, but for practical purposes, extended full ketosis halts autophagy. That is why it prevents a loss of lean body mass!

Autophagy is the product of INTERMITTENT fasting because it occurs during the HUNGRY period entering into a fast. Early fasting hunger is a way to prevent the body from cannibalizing itself. The reason that INTERMITTENT FASTING causes autophagy is because the brain is still glucose dependent and needs to use body proteins for glucose in the first 2-3 days. Once ketosis sets in, autophagy is massively down-regulated and the further you get into a fast and the further you get into ketosis, the less effective fasting becomes for autophagy. I.F. SHOULD make you hungry if the goal is autophagy. Ketones will curb hunger but that is because they replace autophagy derived glucose so the body stops destroying itself. EXTENDED fasting IS a good way to loose fat without muscle loss because autophagy is staunched. INTERMITTENT fasting works for autophagy because carb dependent (non ketone adapted) tissues are deprived of glucose in the 18-42 hour window before ketosis kicks in and so damaged cell proteins get identified and destroyed by the immune system. IF only works for autophagy if tissues are returned to a glucose dependent state “intermittently”. Hunger is a sign of autophagy. Lack of hunger in a deep fast or ketosis is a sign of low autophagy due to a lack of dependency on autophagy derived proteins that are turned to glucose. Autophagy also becomes largely unnecessary for health in ketosis because precancerous cells are starved to death rather than needing to be autophagized. IF does not preserve lean body mass (although LBM may be preserved given adequate nutrition during the meal period and increased insulin sensitivity that acts during that period). Lean body mass loss during an extended fast stabilizes in 2-3 days when the fast has become extended and ketones start to take the place of glucose. IF occurs in 18-42 hour windows between “meals” that upregulate glucose dependency (by consumption of enough carbs to turn off ketosis). Calorie restriction and intermittent fasting both cause autophagy. Extended fasting burns fat while preserving muscle but largely blocks synthesis of new proteins.


some really good points here. as someone who’s done IF (16/8, ADF, warrior diet etc) for probably 10 years now… can definitely say there is some desensitizing going on .

you know that feeling when you were a beginner (kind of bulky, eating lots of carbs and first time trianing??)…muscles pumped and engorged.

after training for a long time, especially fasted training, muscles have become stringy, harder to pump (even using plazma).

the honeyhmoon period of IF (first few months) can actually dissipate. few people care to talk about it (sticking w/ IF as a “lifestyle”) and there are some interesting hormonal impacts longer term. hardly any studies on this (who the fuck cares right??) but each user should watch out.

and i suspect the same thing happens w/ long term keto folks as well


Thank you so much for the reply Christian, really appreciate it!

Do you think this holds true especially for type 2’s? I’m a type 2a and have been dealing with lots of energy crashes lately. Since I made sure to eat more during the day and added a protein shake in the morning with some extra tyrosine (500-1000mg), I’ve been doing much better. So it’s not IF anymore, but I do feel better though.