Intermittent fasting

[cornivore]

As far as periodic fasting (PF) goes, especially, I don't think it can do much good to skip the micronutrients, any more than skipping electrolytes on a hot day. So I was looking into studies related to that.

After a dangerously long fast, the first thing they recommend doing is getting micronutrients prior to eating: "All guidelines recommend that vitamin supplementation should be started immediately, before and for the first 10 days of refeeding"[1]. So obviously if those vitamins weren't skipped in the first place, it would be less dangerous. Along those lines, another study indicates that something like a multivitamin is probably as effective during a fast as it is after eating: "Iron absorption values obtained when the supplements were administered to fasting women were not significantly different from those obtained after postprandial administration"[2]. Several studies also show that taking a multivitamin acutely improves cognitive function, the most relevant one being that "MVM supplementation appears to potentially offer an effective intervention in the dietary restriction regimen to combat daily life physical and mental stress"[3]. In general it was determined that "there was no clear decrease or increase in mortality from all causes, cardiovascular diseases, or cancer among multivitamin supplement users"[4], yet food is fortified because vitamin deficiencies occur, so basically it couldn't hurt to take a vitamin, or it would most likely help prevent the complications associated with fasting or energy restriction, which is mostly about macronutrient restriction, and its benefits don't seem to be related to micronutrient restriction.

In other words, I don't see any evidence in favor of fasting to limit micronutrients. There seems to be more evidence that they shouldn't be limited, unless it's a specific medical intervention. Besides, most people don't do absolute fasts intermittently, they at least drink water, and should probably at least take a vitamin too, or sometimes electrolytes (for thermoregulation and extended fasts). Intermittent vitamin-mineral supplementation has been shown to be effective also (which would be well timed during a "health fast" then). This could be referred to as a form of "fasting mimickry" too, although that diet usually gets into incorporating some macronutrients, for the sake of eating with an end result similar to fasting. Well, I'm not looking for an excuse to eat during a fast, but fasting has its limitations anyway (you know, it is in itself a limitation, or a question of what you want to limit).

1. Refeeding syndrome: what it is, and how to prevent and treat it
2. Effect of food on the availability of iron from three multivitamin/mineral supplements during pregnancy
3. Effect of chronic unpredictable stress on short term dietary restriction and its modulation by multivitamin-mineral supplementation
4. Multivitamin Use and the Risk of Mortality and Cancer Incidence

• Multivitamins and minerals modulate whole-body energy metabolism and cerebral blood-flow during cognitive task performance
• Acute Effects of Different Multivitamin Mineral Preparations on Mood, Cognitive Performance and Functional Brain Activation
• A periodic diet that mimics fasting promotes multi-system regeneration, enhanced cognitive performance and healthspan
• Relationships between micronutrient losses in sweat and blood pressure among heat-exposed steelworkers

[cornivore]

Another thing is that a potential risk factor of going without micronutrients, while on a water fast, would be that one could accumulate more toxins from the water.

Micronutrients interact with toxic metals at several points in the body: absorption and excretion of toxic metals; transport of metals in the body; binding to target proteins; metabolism and sequestration of toxic metals; and finally, in secondary mechanisms of toxicity such as oxidative stress. Therefore, people eating a diet deficient in micronutrients will be predisposed to toxicity from nonessential metals.—Effects of micronutrients on metal toxicity

We found several instances of high heavy metal concentrations in plasma samples despite all water samples testing below EPA limit—Assessing Heavy Metal and PCB Exposure from Tap Water...

Alrighty then. My educated guess about it will be that I'd either want to do an absolute fast, without any food or water, or take a multivitamin-mineral supplement, if I were doing a water fast, along with mixing into it the daily value of electrolytes with some sugar to maintain a normal fluid balance, because simply drinking water can upset the fluid balance, etc. I'm talking about a 48 hour intermittent fast, which is long enough for a fluid imbalance to have consequenses, perhaps (so I'll plan on including the full micro-meal deal with that).

By the way, even the vegan diet itself may be considered a form of fasting under certain circumstances:

This plan resembles a vegan diet, which has been reported to yield health enhancing properties. However, a Daniel Fast is more stringent, in that aside from the exclusion of all animal products, there are no processed foods, white flour products, preservatives, additives, sweeteners, flavorings, caffeine, or alcohol allowed in this plan.—Effect of a 21 day Daniel Fast on metabolic and cardiovascular disease risk factors in men and women

[cornivore]

Humoring myself here, but maybe I can do various kinds of fasting together... Now I'm trying out an inter-intermittent fast, which for me is an absolute (dry) day of fasting in between two fluid fasting days (which include micronutrient supplements and a couple of homemade sports drinks), and those would be in between two days of eating (so this is like an 80 hour fast, in theory). It's going okay, I'm on the absolute fast today, which will be my first day of consuming nothing. Well, what can I say, it's kind of boring (but I can remind myself that it is restful, which is a good kind of boredom). I'd make the distinction between the two by reserving exercise that involves sweating only for fluid fasting days. I have enough weight to lose that it shouldn't be too draining, given there's stored energy that I'm wearing around... I'll be looking forward to finding out how much I can adapt to fasting at a minimum bodyweight (like just above that defined by health department standards, as far as what constitutes being underweight). Until then, all I know is that when I eat every day, I tend to gain weight. In the last two or three weeks I skipped the intermittent fasting to experiment with recipes, but didn't eat a whole lot either, and still gained 14 pounds. Then again, I've lost half of that in the middle of this fast so far, even though it included fluids. So it could go either way, as to whether I can do intermittent (or inter-intermittent) fasting, long term, depending on how effeiciently I use energy at a lighter weight. My guess would be that I'd have to eat more often, but now is a good time to experiment with eating less often, so what the hell... I think it couldn't be worse than indigestion is otherwise (well, having nothing feels peaceful really, as long as a normal amount of sleep is involved, and my pulse rate seems to have slowed today, so no wonder).

There's an old book (I skimmed) about a doctor going Forty Days Without Food. He lost 36 pounds, and wasn't sweating a lot in the process, which included drinking water. This was before they knew about refeeding syndrome, or rehydration therapy, so to some extent he got lucky, I'd say (not to take away from his achievement there). I tend to agree with what he said about digestion, which got me interested me in the topic.

It is an unquestionable fact that the custom of eating three times a day gives the various organs of the body too much work to perform...

Anyway, I think that's an opinion, and am not recommending my kind of fasting to anyone else, because maybe it's personal, if not impossible (just saying there's more scientific evidence behind it these days—actually that medical supervision would be advisable, especially for something like breatharianism, which ignores scientific evidence). The funny thing is, I've never heard of medical supervision for overeating, which causes more disease (or at least there's a more immediate danger of choking than running out of enough energy to swallow).

As far as sports medicine goes, I think the timing of sports drinks during "fasting" can also make a difference, depending on what you're doing.

Postexercise muscle glycogen synthesis is an important factor in determining the time needed to recover from prolonged exercise. —Maximizing postexercise muscle glycogen synthesis

If carbohydrates are withheld for two hours post exercise, it can reduce the rate of glycogen synthesis by 47%, compared with feeding CHO immediately after exercise.—Hydration and Temperature in Tennis

So there's more of a benefit to consuming sugar water for exercise performance and recovery, beyond its effect of balancing electrolytes and water absorption. To a point anyway, they say too much sugar can have the opposite effect (during exercise at least). There was also a study of the Impact of Ramadan on physical performance in professional soccer players, which indicates (at least) that their recovery times were slower, because they were not eating soon enough after prolonged exercise.

Ramadan is a period of daylight abstention from liquid or solid nutrients. As sports continue to be scheduled, an understanding of the effects of Ramadan on Muslim athletes is warranted...

Performance declined significantly (p<0.05) for speed, agility, dribbling speed and endurance, and most stayed low after the conclusion of Ramadan. Nearly 70% of the players thought that their training and performance were adversely affected during the fast.

It seems they would also need something like a sports drink during exercise, especially several hours after eating.

Performance of repeated anaerobic exercise is impaired, but aerobic power and muscular strength show little change during Ramadan. Ratings of fatigue are increased, and vigilance and reaction times are impaired, particularly during the afternoon. Medical issues during Ramadan are few.—Ramadan and sport

The majority of studies on Ramadan suggest that it has health benefits, as a form of intermittent fasting. As for impaired performance, I seem to benefit from something like peppermint candy along with the fluids (it's a kind of stimulant), so I'll throw that in there as needed to give myself a sporting chance. It's all about homeostasis, fundamentally, so different circumstances require different dietary measures (which is one reason why there are so many kinds of fasting, or diets in general). They can be combined intermittently too. How exciting! I bet there's enough of a variety to do a different diet every day of the year... yet I've never tried a restrictive diet other than veggies (and intermittent fasting lately). My guess is that I could do this combination for 6 months before I lost too much weight (given that I could stay interested in eating litte to nothing for that long, maybe it's an acquired tastelessness, but I think maintaining a fluid balance and getting enough rest prevents hunger, or that's an aspect of being overweight as well, time will tell).

One trick for absolute fasting is not talking too much, I think, since it would make me want to drink. Practically speaking, I'd say that a few sips of water would be okay, but the idea is to keep it to an absolute minimum (so I'd better shut up for the rest of the day)...

[cornivore]

Yeah, that works (for me). I made it through the day without anything to eat or drink, and felt great the next morning. I didn't even want to resume the fluids, but felt fine when I did that too. Somehow I lost another three pounds in the process, and hadn't done any sweating or much peeing (excuse me, it's nice to give that a rest). So I should be able to keep this going inter-intermittently until the extra weight is off my plate.

Well, at the end of the day (or days), I'm not sure if I want to keep it going to such an extreme, since the exercise I planned on doing would make it seem that way. Those are probably conflicts of interest, and I'll likely reserve the extended fasting for when I'm older and want to relax most of the time. It's a nice experience, but also conditional I think. Still, I feel like I can do the exercise, but recovering from it is a known problem (in sports science). A more sporty fluid fast should be enough for me to get the most out of it (in a shorter period of time). I may do more of that absolute fasting once in a while (since I like it better, but usually have other things to do—well I don't know, it's hard to call fasting a luxury too).

[cornivore]

Aside from competetive sports, it isn't necessarily all or nothing between exercise and eating vs fasting, as other info indicates that recovery from exercise can be done while fasting, but would have a better chance of turning out okay if exercise was done only once a day.

In conclusion, during recovery from exercise, it is possible for skeletal muscles to replenish their glycogen stores under conditions expected to be highly unfavourable to glycogen synthesis such as fasting or active recovery. The rates of muscle glycogen synthesis can be very high under these conditions, most probably because of the acute activation of glucose transport and glycogen synthase and inhibition of glycogen phosphorylase. This capacity of skeletal muscles to replenish their glycogen stores under extreme conditions is clearly advantageous as it allows muscles to maintain adequate levels of glycogen stores for fight or flight responses.

In fact, we store just enough glycogen to sustain our energy demands for only a few hours of intense aerobic exercise, and so little glycogen is stored in our muscles that close to a third to half of these stores can be depleted within a few minutes of a maximal sprint effort.

—Post-Exercise Muscle Glycogen Repletion in the Extreme: Effect of Food Absence and Active Recovery

During fasting, animals maintain their energy balance by shifting their energy source from carbohydrates to triglycerides... A sufficient energy supply is essential for life; consequently, multiple mechanisms have evolved to ensure both energy availability and conservation during fasting. During fasting, liver glycogen, a glucose-storage polymer, is initially mobilized to replenish blood glucose (glycogenolysis). Major changes in metabolism are known to occur as the glycogen supply dwindles; when glycogen storage in the liver is depleted, stored adipose tissue triglycerides are released into the circulation as fatty acids and glycerol. The released fatty acids are directly oxidized as an energy source by some tissues (liver and muscle), or are metabolized by the liver to ketone bodies for use by tissues, notably the brain that cannot utilize fatty acids, while the glycerol is converted by the liver into glucose (gluconeogenesis).

—Glycogen shortage during fasting triggers liver–brain–adipose neurocircuitry to facilitate fat utilization

These results demonstrate that in humans blood glucose concentration is maintained at normal levels during exercise after fasting despite the depletion of liver glycogen. Homeostasis is probably maintained as a result of increased gluconeogenesis and decreased utilization of glucose in the muscle as a result of lowered pyruvate dehydrogenase activity.

—Metabolic responses to exercise after fasting

The restoration of muscle glycogen after depletion by exercise is a central component of the recovery process. To maximize the rate of muscle glycogen storage during short-term recovery, it is important to consume a carbohydrate supplement as soon after exercise as possible... However, the efficiency of muscle glycogen storage can be increased significantly with the addition of protein to a carbohydrate supplement. This will reduce both the amount of carbohydrate and frequency of supplementation required to maximize glycogen storage.

—Regulation of Muscle Glycogen Repletion, Muscle Protein Synthesis and Repair Following Exercise

When the period between exercise sessions is < 8 h, the athlete should begin carbohydrate intake as soon as practical after the first workout to maximize the effective recovery time between sessions.

—Carbohydrates and fat for training and recovery

Nutrient administration following an exercise bout vastly affects anabolic processes within the human body, irrespective of exercise mode. Of particular importance are protein and carbohydrates whereby these two macronutrients portray distinct functions as anabolic agents.

—The Role of Post-Exercise Nutrient Administration on Muscle Protein Synthesis and Glycogen Synthesis

When ingested in the form of glucose–fructose mixtures (or sucrose), not only is this ingestion rate more tolerable due to lower gut discomfort but total body glycogen status can also be enhanced over glucose (polymer) ingestion alone, due to greater liver glycogen repletion.

—Glucose Plus Fructose Ingestion for Post-Exercise Recovery—Greater than the Sum of Its Parts?

Glycogen is the storage form of carbohydrates in mammals. In humans the majority of glycogen is stored in skeletal muscles... A main function of glycogen is to maintain a physiological blood glucose concentration, but only liver glycogen directly contributes to release of glucose into the blood... We believe that the main function of skeletal muscle glycogen, from an evolutional point of view, is to serve as an energy store in "fight or flight" situations.

The glycogen content increases slightly by acute intake of large amount of carbohydrates. However, an acute bout of glycogen depleting exercise can double glycogen content in skeletal muscles if high amount of carbohydrates are ingested for 3 days; this phenomenon is called super compensation. The glycogen content is higher in endurance trained subjects compared to untrained subjects, and glycogen content increases in muscles after endurance training. In contrast, prolonged intake of high amount of carbohydrates does not increase glycogen content in skeletal muscles, and the excess carbohydrate ingested is converted to lipid.

The relative (as well as absolute) rate of carbohydrate oxidation depends on exercise intensity and well-trained persons have a much higher capacity to metabolize glucose and fat compared to untrained persons. During exercise above 70% the major carbohydrate source is muscle glycogen.

Both exercise and fasting decrease glycogen in the muscle where supercompensation occurs, but is not understood why glycogen content is increased after glycogen depletion.

Decreasing glycogen content by exercise or fasting stimulates glycogen accumulation to levels above the glycogen content in well-fed conditions.

—The Role of Skeletal Muscle Glycogen Breakdown for Regulation of Insulin Sensitivity by Exercise

In conclusion, 24-h fat oxidation was increased by exercise only when performed before breakfast under energy-balanced conditions. Significant exercise-induced transient energy deficits, which are more likely when exercise is performed before breakfast, serve as a cue to increase 24-h fat oxidation.

—Exercise Increases 24-h Fat Oxidation Only When It Is Performed Before Breakfast

There's some overlapping info there, along with what I looked up about micronutrients earlier. There is a cognitive kind of recovery to consider from fasting, relative to sugar as well.

Moderate hypoglycemia, such as that arising from fasting, can impair cognitive performance short-term verbal and spatial memory, and the speed of mental computation... Providing subjects a glucose drink after fasting can improve performance.

—Cognitive cost as dynamic allocation of energetic resources

I suppose if you're going to do something requiring a high level of concentration while fasting, it wouldn't be the best time to exercise prior to that, or at least include an electrolyte drink and multivitamin to compensate during active recovery. I can actually feel a difference of circulation in my head when I do that kind of enhanced fluid fast, versus water or dry fasting, so it seems this explains it. My guess would be that the neuroprotective effects of fasting are not due to the exclusion of micronutrients or sugars that would enhance cognitive function during that sort of fast.

In all species studied to date, restricted calorie intake by 20-50% while providing adequate micronutrient supply significantly extends mean and maximal lifespan. Moreover, age-related deficits in learning and motor coordination are ameliorated by caloric restriction (CR) in rodents.

—Long-term caloric restriction...

A high micronutrient density diet mitigates the unpleasant aspects of the experience of hunger even though it is lower in calories.

—Changing perceptions of hunger on a high nutrient density diet

Vitamins, particularly vitamins B1, vitamin B2, and niacin, are important in the production of energy from amino acids, fatty acids, and glucose. Thus, body vitamin stores may be critical for energy production during starvation. The requirement of these three vitamins increases with energy consumption.

—Excess Vitamin Intake before Starvation...

So if the requirement of some micronutrients increases with energy consumption, it could be especially important to supplement them, if exercising during a fast. Other micronutrients are said to decrease with fasting alone.

Results show that short-term (2 days) fasting significantly decreases iron concentrations in serum and hair, as well as levels of ferritin, hemoglobin, hematocrit, red blood cells, and total iron binding capacity, but the short-term fasting did not influence the other iron management parameters.

The study shows that, through an impact on mineral levels, even short-term food restrictions, as observed in many slimming women and girls, can be a reason for iron deficiency and also can alter the emotional status of healthy women. Maybe depression symptoms in anorexia or other eating disorders patients can be associated with iron deficiencies.

Free-will starvation decreases the quality of life rather than increases, opposite to the popular opinion presented by some people using restricted diets.

—Effect of short-term food restriction on iron metabolism...

I think the last statement about quality of life is simply factual, because nutrition itself is a quality of life; therefore, when it is decreased so is the quality of it (as in life processes). It's a two way street though, overeating also decreases the quality of life as such, because it interferes with those processes. There are aspects of fasting which can increase quality of life, unless there are concurrent micronutrient deficiencies (whether acute or chronic), apparently.

After reading as much about it, I don't really see why people want to distinguish between water fasting, which is most always what "fasting" refers to, and that which would include micronutrients and such, because water includes some minerals anyway (or toxins), and could also cause an imbalance of those which are already circulating. There's no point in that being the standard of fasting, if you had to plan it, because blood is thicker than water, and the sense that water is going to purify your blood is nonsense. It's fair to say that people cannot survive without water for long periods of time, which is what I was thinking about to begin with, but this doesn't mean fasting on it is the best we can do with the concept.

[cornivore]

Is it not catabolic? (I don't want to look like a pencil neck.)

This seems to depend on how long the fasting is. A 24 hour fast isn't necessarily, depending on the individual and their nutrient status, beyond that it would be more likely (if they were exercising during the fast too, or especially if they had low body fat to begin with). Generally, it is said to be catabolic to fat before muscle, as is prolonged exercise.

The urinary excretion of riboflavin in fourteen of fifteen normal subjects increased during a 24 to 37 hour fast. In most subjects, the increased rate of excretion did not start until 13 to 20 hours after the last meal.

The total 24-hour riboflavin excretion during the fast was about twice that for the last day when food was consumed.

Toward the end of the fast, the excretion rate of riboflavin in some subjects was ten to fifteen times that for the control day.

—Elevated Riboflavin Levels in Urine of Fasting Human Subjects

The elevated excretions of riboflavin are indicative of adequate reserves and catabolism of body protein for use as energy, or both.

—Thiamin, riboflavin, and pyridoxine excretion during acute starvation and calorie restriction

Islamic fasting is an intermittent fasting that lasts from dawn to sunset. It differs from other intermittent fasting models, because observants do not drink during the Ramadan fasting period.

The loss of body fat, especially visceral fat, is desirable, but prolonged fasting can trigger a catabolic state, thus increasing gluconeogenesis with proteolysis, which ultimately decreases protein mass.

The catabolic state, which is related to protein loss, was not triggered during Ramadan fasting.

—Ramadan Fasting Decreases Body Fat but Not Protein Mass

Metabolically, early fasting is characterized by a high rate of gluconeogenesis with amino acids as the primary substrates.

—Fasting: The History, Pathophysiology and Complications

amino acid catabolism during exercise is important for three reasons: 1) for free energy during exercise to fuel muscle contraction; 2) to increase concentrations of citric acid cycle intermediates and therefore support carbohydrate and lipid catabolism; and 3) to serve as gluconeogenic precursors

—Metabolic Effects of the Very-Low-Carbohydrate Diets

As fasting continues, progressive ketosis develops due to the mobilization and β-oxidation of fatty acids and the increase in ketone bodies (KBs) (e.g., β-hydroxybutyrate) that replace glucose as the primary energy source in the CNS, thereby decreasing the need for gluconeogenesis and sparing protein catabolism.

If starvation continues until the adipose stores are depleted, muscle is rapidly degraded for gluconeogenesis, potentially leading to a lethal outcome.

—Metabolism during Fasting and Starvation

In both climates subjects with lower initial body fat percentages lost significantly more muscle mass than subjects with higher initial body fat percentages. There was no significant relationship between macronutrient intake and muscle mass loss for either sex.

—Body fat attenuates muscle mass catabolism among physically active humans...

An important finding in this study is that every-other-day fasting (EODF) can effectively restore deficiencies in fat catabolism

—Metabolic adaptation to intermittent fasting...

Urinary acetoacetate levels were higher during the IF period suggesting a constant lipid catabolism.

—Comparison of Intermittent Fasting Versus Caloric Restriction in Obese Subjects

It is also said to involve muscle catabolism somewhere in between short and long term continuous fasting.

Adapting to starvation requires an interorgan integration of the activity of metabolic pathways to protect the body from an irreversible loss of resources (1, 2), but how the organism integrates these reactions remains largely unknown. Numerous studies on humans, who fasted for 3–6 weeks, have shown that glycogen stores are depleted within a day (3). The decline in circulating glucose and insulin during the next few days (4) induces a transient increase in plasma (essential) amino acids and a concomitant decline in plasma alanine levels due to an increased hepatic extraction for gluconeogenesis (5, 6). Muscle catabolism is a major source of amino acids in this phase. When fasting is continued, muscle protein catabolism declines, and hepatic uptake of amino acids decreases, which is reflected in a decline of endogenous glucose production (6) and urinary nitrogen excretion (4, 7). Lipid catabolism and the (hepatic) production of ketone bodies also increases rapidly and is quantitatively similar after 3 days and 5–6 weeks of starvation (8), but plasma levels increase only gradually to plateau after 4 weeks (4, 9). The associated increase in urinary ketone body (organic-acid) excretion requires a compensatory increase in ammonia production and urinary excretion (4, 7, 10), which is met by an increased renal amino acid uptake and gluconeogenesis (5, 6). As a result, the kidney and the liver produce similar amounts of glucose (4, 6) and ammonia/urea (7) after 2–3 weeks of fasting. From the third week onward, the circulating level of β-hydroxybutyrate has become sufficiently high to replace glucose as the fuel in e.g. the central nervous system (11), but amino acids continue to be catabolized at a low rate (12) because some tissues (erythrocytes) need glucose as fuel, whereas the kidney needs to produce ammonia. This large body of metabolomic data describes an essentially biphasic response with an early phase in which proteins and fats are equally used as energy sources and a late phase in which proteins are maximally conserved.

—Interorgan Coordination of the Murine Adaptive Response to Fasting

[Jebus]

Thank you @cornivore .

Could you summarize all this research into a few sentences, i.e. what fasting protocol would you recommend for other vegans?

[cornivore]

No problem, I'd recommend that anyone who is looking into fasting, as a way of life, should read up on some of the research, or consult a physician, or both.

Here's an example of why...

Our study suggested that there was an increase in accidental and natural deaths and a decrease in suicide and homicides in Ramadan.

—Evaluation of forensic deaths during the month of Ramadan

These people are following a fasting convention, but don't necessarily understand what they're doing, and more accidental deaths are occurring because of it (e.g., Low normal fasting glucose and risk of accidental death). Accidents happen, but not as often if you know what you're doing (and that's also a personal question to answer for yourself, or along with consultation). Physiological stress can affect different people in different ways at different times (e.g., sudden death during prolonged religious fasting). Likewise, I was reading about a hiker in his twenties who set out to fast for a few days in the wilderness, and his remains were found the next year... of course, he thought he knew what he was doing, but didn't, so play it safe!

[cornivore]

During fasting, activation of the counter-regulatory response (CRR) prevents hypoglycemia.—Fasting induces a form of autonomic synaptic plasticity that prevents hypoglycemia

In light of accidents being more likely when serum glucose is low, other studies indicate that some people have impaired counterregulatory hormone responses, and hypoglycemia can occur along with energy/carbohydrate restriction at times.

The methods used by athletes for achieving rapid body mass loss (RBML) may cause dehydration, an increased load on the cardiovascular system, impairment of the thermo-regulatory system, depletion of glycogen stores, hypoglycemia and loss of body protein, electrolytes and vitamins.
—Acute Effects of Self-Selected Regimen of Rapid Body Mass Loss...

If this occurs often, its onset may not be sensed either.

Glycemic thresholds for symptoms of hypoglycemia shift to lower plasma glucose concentrations following recent episodes of hypoglycemia, leading to the syndrome of hypoglycemia unawareness--loss of the warning symptoms of developing hypoglycemia.
—Symptoms of hypoglycemia, thresholds for their occurrence, and hypoglycemia unawareness

Hypoglycemia can happen suddenly. It is usually mild and can be treated quickly and easily by eating or drinking a small amount of glucose-rich food. If left untreated, hypoglycemia can get worse and cause confusion, clumsiness, or fainting. Severe hypoglycemia can lead to seizures, coma, and even death... Signs include hunger, nervousness, shakiness, perspiration, dizziness or light-headedness, sleepiness, and confusion.

It would be a good idea to have some glucose-rich fluid or food handy, since hypoglycemia can happen suddenly. Of course, if you notice a personal trend of it, which seems to occur along with fasting, the glucose should be supplemented as a part of fasting from then on, so it doesn't recur, or unawareness of the symptoms may develop otherwise, and that could be especially dangerous.

Nervous system function in the intact animal depends on substrates supplied by the blood, and no satisfactory, normal, endogenous substitute for glucose has been found. Glucose, therefore, must be considered essential for normal physiological behavior of the central nervous system.

In contrast to most other tissues, which exhibit considerable flexibility with respect to the nature of the foodstuffs extracted and consumed from the blood, the normal brain is restricted almost exclusively to glucose as the substrate for its energy metabolism.
—Substrates of Cerebral Metabolism

A ketogenic diet is said to perpetuate a hypoglycemic state... "The diet has been used successfully to treat patients with epilepsy", although one of its complications is symptomatic hypoglycemia (Food for Thought). "This physiological condition, i.e., ketosis, can be reached through fasting or through a drastically reduced carbohydrate diet (below 20 g per day)".

One interpretation of these data is that children with ketotic hypoglycaemia have abbreviated fasting tolerance due to accelerated starvation... Similar accelerated starvation occurs in lean compared to obese individuals, in adult women compared to adult men, in children compared to adults, and in pregnant and lactating women compared to non‐pregnant women. It is possible that children with ketotic hypoglycaemia merely represent the lower end of the bell shaped curve for fasting tolerance in children. Their symptomatic episodes of hypoglycaemia might simply reflect what could occur in other children if the usual overnight period of fasting were 18 instead of 12 hours.
—Parsing ketotic hypoglycaemia

Apparently not everybody responds to fasting in the same way (or perhaps not even the same person on a different day, like if you used to be a fat man, when you began fasting, and then lost weight).

Hyponatremia can also present with minimal symptoms which overlap those of hypoglycemia, and they say that even "mild hyponatremia is associated with subtle changes in gait and associated with increased risk of fractures" (and "has an effect on cognition, balance and attention"), or that a "mild degree of hypokalemia is treated because of risk of cardiac arrhythmia", and that "in patients with arrhythmias, the most feared complication while driving is of driver incapacity resulting in a road traffic accident". So in addition to the glucose, those electrolytes are perhaps vital to include in the fasting practice, or have with you (just in case). Right, I was talking about the sports drinks earlier, and here we've found a few more reasons for something like them, besides sports, or I'd think of fasting as a sport of some sort (if not a death match), since similar things are happening with recovery there.

[cornivore]

What fasting protocol would you recommend for other vegans?

I think it's intermittent eating, all the same, because one's body feeds on itself too, ew... Is that vegan?