Hunger and Performance
If you haven’t already done so, please read part 1 first. It is necessary for the assessment of this article. The introduction and conclusion are mandatory. While you’re at it, read the middle too.
In this article, you will learn about
- how hunger increases performance,
- the fasting physiology and hormones,
- how fasting makes you stronger and improves your endurance,
- how to build muscle and lose fat at the same time with intermittent fasting.
Hunger in its natural context
It’s a typical Sunday noon. I’m writing and my empty stomach is growling. But I won’t eat until after my evening training.
Why am I doing this?
The reason is simple: I do my best work when I’m hungry.
To understand this, we have to look at the true nature of hunger:
Hunger → Activity → Eating
That is, living things get hungry and then actively search for food. Every organism has to move –mentally and physically– in order to eat and hunger helps with that.
Hunger increases performance.
Ironically, we are the only species where this logic doesn’t seem to apply anymore –at least at first sight.
In part 1 we’ve learned that hominid evolution and frequent involuntary food abstinence went hand in hand. The hunger had to get our early ancestors moving. Otherwise, survival and further development wouldn’t have been possible. Consequently, our genome and bodily systems are well adapted to periods of fasting –and we may even thrive on that (i. e. hormesis).
Nowadays, there are two kinds of hunger:
- True hunger (the natural one)
- False hunger (the artificial one)
The former is a vital signal which results from a basic physiological need –the need to eat. Due to its necessity for survival, the genetic encoding for true hunger is deeply rooted within our DNA. Everyone and every animal carries it. In times when food is scarce, the true hunger gradually rises and aligns bodily systems for food procurement (e. g. hunting).
Thus, hunger shall make you active and motivated, not lethargic and grumpy.
Nevertheless, the prevalent manifestation of today’s hunger entails the latter feelings and affected people are more of the hangry kind. No one would dare to associate an empty stomach with increased mental and physical performance.
This sensation is because most people are experiencing false hunger which sets in before true hunger does. The false hunger shows itself with a sudden and great urgency which stands in no proportion to the actual need for food. It saps your energy and willpower away and you will feel like starving, even though you’re still well nourished from your last meal.
False hunger, by contrast with true hunger, is not inherited. It’s a matter of habit, or, in other words, a conditioned response –and Pavlov sends his regards.
Your body and mind get used to your particular feeding behavior. When you’re given the right cue –e. g. through media, specific times (8 a.m. breakfast, 12 a.m. lunch, 6 p.m. dinner), specific locations, boredom, blood sugar returning from sky-high to normal, the mere sighting of snacks, or social get-togethers– you’ll get hungry and eat something regardless of an actual physiological need.
You’re hungry when, in fact, you aren’t.
Take it from me, it is absolutely possible to unlearn the onerous false hunger and experience the performance-boosting effects of true hunger instead. The easiest way for this is, you’ve guessed it, intermittent fasting. Hunger will eventually become pleasant and vitalizing.
It’s a powerful and liberating experience that you can go many hours without food and suffer no drop in performance, or better yet, increase your performance.
You will go from mindless gorging to mindful eating. A meal will become a fulfilling experience again instead of a sheer compensatory mechanism.
Now, how can consuming no energy lead to more perceived energy?
Life in the fast lane – The physiology and hormones during fasting
*Two important points in advance:
1) This article is about short-term fasting (14-22 hours) and training in the fasted state.
2) You can’t out-fast a bad diet, nor a lack of squats and deadlifts in your training regime.
You enter the fasting state once your body assimilated all nutrients from your previous meal. This includes the absorption of nutrients after digestion and its transformation in biological tissues and fluids. The whole process takes anywhere from 3 to 10 hours –depending on meal size, composition and GI-tract functionality. Now, in the so-called post-absorptive state, your body taps into its own energy stores to maintain homoeostasis.
Under normal circumstances, you wake up fasted in the morning.
Now, your body secretes its stress hormones and, when you skip breakfast, will continue to do so.
The increase in the amount or sensitivity to
- cortisol (physiological cortisol awakening response),
- human growth hormone (HGH),
- and probably dopamine,
while insulin levels are low, will crank up your body and mind.
You start your day as a fat-burning machine with a sharp and aggressive focus –which is exactly what you’ll need for hunting.
Catecholamines, like adrenaline, and human growth hormone act protein-sparing, so there is no need to worry about muscle loss. Imagine how unfortunate that would have been for our evolution.
Noradrenaline revs up your metabolism. You’ve read correctly, short-term fasting, not frequent small meals, increase your resting metabolic rate. This makes sense if we also take the energizing effects of adrenaline and dopamine into account. In times of hardship (e. g. food shortage) you better mobilize your posterior if you care about surviving.
Hunger aims all processes at foraging.
This becomes even more evident when we look at the main hunger hormone ghrelin (acronym: “growth hormone release inducing”). Your body secretes it when you haven’t eaten for some time and blood levels drop once you eat.
- hunger (no surprises here),
- cardiac output and vasodilation,
- dopamine concentration in brain areas responsible for eye movement, motor planning, reward-seeking behavior, learning and addiction,
- and neurotrophins in brain areas responsible for learning, memory and spatial thinking.
These effects fit perfectly into the natural context of hunger.
Ghrelin makes you hungry, mobilizes energy stores, allows for better nutrient uptake and prepares for growth (more on this later). It gives you the prospect for reward, makes your movements energy-efficient, enhances spatial orientation and improves your memory. In fact, ghrelin is seen as “essential for cognitive adaptation to changing environments and the process of learning”.
Ghrelin is the reason why hunger motivates us and why it’s hard to perform at your physical –let alone intellectual– peak after a decadent Thanksgiving meal.
Furthermore, ghrelin secretion is trainable. It adapts to the habitual meal frequency. The entrainment of Ghrelin is what makes fasting effortless once it becomes a habit.
Hunting on an empty stomach – Fasted strength and endurance training
Note: Solid research about fasted training is, generously said, scarce. Most of the existing studies have been done within the framework of Ramadan fasting and involve fluid restriction which isn’t the best of ideas if you’re after performance. And there is also the issue of familiarization because fasted training can “catch you off guard” physiologically and psychologically if you’ve never done it before. After a period of adaptation, however, I think most people should be able to train fasted without a drop in performance. I, for one, even increased my performance during strength training. Keep in mind that there are, however, people whose performance will drastically suffer when training fasted. I do not recommend it for them. Experiment and see for yourself.
In what follows, I’ve tried to conceptualize a working model for fasted training from the bits of relevant research, theory, and my own experience which could help to explain an increase in performance.
Focus and strength
The focus and strength during fasted training are the best I’ve ever had.
I assume this stems from the increased sympathetic tone and psychoactive effects of the catecholamines. Fasting and strength training, in particular the combination of the two, upregulate sympathetic activity –thus drive a potent fight or flight response.
Combine this with pre-workout caffeine, driving music, and the obligatory intra-workout tasteless chewing gum and you’ve got yourself a recipe for tunnel vision.
There is a potential benefit of keeping carbohydrates at a minimum before working out. For one thing, it enables your motor neurons to fire with a greater amplitude which in turn enables harder contractions and fine(r)-motor control. The same probably applies to some degree to fasting as well.
Your psychomotor performance increases which describes the ability to perform coordinated movements –also under heavy iron.
Furthermore, fasting or low-carbohydrate diets plus training a) lower the stimulus threshold of adrenal glands to release catecholamines, b) increase the amount of adrenaline, and c) increase the cells sensitivity to adrenaline. You’ll produce more of it at a faster rate and are able to better utilize it. Triple threat.
I like to train after up to 16-20 hours without food because at this time my state of mind is excellent. I feel calm, happy and concentrated, yet highly vigilant, aggressive and motivated. These effects may seem paradox, nonetheless, I’m only speaking from my own experience, shaped by the pleasantly irritating emotional conglomerate during training.
Longer fasts already have been shown to improve mood –probably through an increased brain-availability of serotonin, endogenous opioids and endocannabinoids.
The glycogen stores in your muscle are reserved for strenuous activity and remain almost untouched after 24 hours –assuming no physical exertion. Your muscle is smart so it oxidizes fatty acids, and possibly ketone bodies, until energy demands run high or you’re approaching momentary muscular failure.
Now, muscle glycogen comes into play. You’ll have plenty of it for your fasted training session.
I’m writing this under the assumption that you have a decent metabolic flexibility –the ability to switch back and forth between fat and glucose for energy-production– and that you’re good at sparring glycogen, or rather at burning fat.
As a medic I’m not often the bringer of good news but anyways: Fasting probably improves both parameters.
Your body will upregulate fat burning when it has to. Like when you’re fasting and training on empty. This will lead to an increase in mitochondrial biogenesis and more proteins for the lipid metabolism which I won’t discuss in detail here. Having a higher amount of (functioning) mitochondria is generally regarded as a good thing and stands in direct proportion to health and performance.
All in all, your oxidative capacity increases which is a measure of mitochondrial density and how much energy you will make through burning fat. This makes perfect sense since body fat is in essence excess food stored in your body for times when there is nothing left to eat except for your own tissue, whereas muscle glycogen constitutes an emergency substrate for fight or flight situations.
By postponing the metabolic shift (fat –> glycogen), you’ll save the precious stock of glucose up to the point where you really need it –when you approach the anaerobic threshold and muscular failure.
Some of the benefits of sparing glycogen could be less lactate formation, better regeneration and more efficient fat-burning.
It is important to replenish your glycogen stores but you should only do so when your muscle is increasingly receptive to glucose.
The glucose uptake and tolerance are directly linked to insulin sensitivity. Intermittent fasting increases whole-body insulin sensitivity, as does fasted training. Additionally, through hard contractions during strength training the muscle cell translocates glucose transporters (GLUT4) insulin-independently to its surface, thus further facilitating muscular glucose uptake.
An increase in insulin sensitivity also means that insulin simply works better and that less insulin is needed for the same effects –e. g. for shuttling glucose into the cell.
The concept train low, compete high has already established itself –particularly in aerobic sports. Furthermore, training in the fasted state improves endurance parameters, boosts VO2max and peak power, increases muscular glycogen stores after re-feeding and reduces glycogen breakdown.
When the circulating glucose levels are low, the capacity of storing glycogen in the exercised muscle increases, whereas the stress-dependent depletion decreases.
There is also some evidence that intermittent fasting could help you build muscle –or rather, that fasting sets the stage for growth. Fasted strength training stimulates the intramyocellular (=inside the muscle) anabolic response to a carbohydrate/protein mixture. This seems to work over an increased phosphorylation of p70S6K which functions as a part of the signaling pathway that includes mTOR –a key player in growth and proliferation. One of the possible effects is a faster shuttling of amino acids into the cell, leading to a higher intracellular amino acid concentration available to activate anabolic pathways.
It is also thinkable that the increased sensitivity to insulin, high HGH levels and, after strength training and ensuing protein intake, higher IGF-1 levels (which activate p70S6K/mTOR), bump up your anabolic machinery. However, this is only speculation from my side but it would make sense in an evolutionary light and since the three hormones share axes and mode of actions.
On a side note: We know that fasting and caloric restriction can decrease excess body fat and reduce plenty of undesirable inflammation markers. We often forget that but having global inflammatory processes in your body will massively hinder muscle growth. Your body always invests in health preservation prior to luxury goods.
Connecting the dots: The principle of supercompensation
All of these effects make sense if we apply the principle of supercompensation to the cellular level. You do something that stresses the cell –taking something essential away or damaging it– and thus create an increased need for that particular thing. Hence, the cell will initiate adaptation processes with the intent of being better prepared next time. It will provide more receptors, transporters and enzymes with the objective of synthesizing, repairing, and hoarding the thing in demand.
With fasting plus training on empty it’s like an anabolic rebound. Through the maximal catabolic stimulus your cell will try to supercompensate by maximizing the potential of becoming anabolic. It will build more mitochondria, translocate nutrient-transporters, improve insulin sensitivity, increase glycogen synthase and activate growth pathways to get ready for uptake, synthesis and growth.
Up to a certain point –when eustress turns to distress– the following applies: The greater the interruption of homeostasis the greater the adaptation. Fasting and exercise activate common pathways –some even say that fasting mimics exercise (I agree to an extent)– thus it’s thinkable that they mutually potentiate one another.
That’s why fasted training is so effective. That’s why train low, compete high works and that’s why fitness-masochists will do hill sprints with empty muscle glycogen stores.
*On a cellular level, most of the fasting- and exercise-related metabolic effects can be traced back to the activation of AMPK –an intracellular energy-sensor which we’ll examine in more depth in another installment. When energy levels fall (characterized by an increase in AMP /ADP:ATP ratio), AMPK acts as an intermediary in an orchestrated network together with PGC-1-α (the master regulator of mitochondrial biogenesis) and the sirtuin family to shift processes from anabolic (ATP-consuming) to catabolic (ATP-producing) and promote metabolic fitness. This triumvirate is responsible for most of the health- and longevity-related effects of fasting and exercise –like reducing oxidative stress, lowering inflammation, repairing of DNA-damage and improving cellular energy metabolism. Activation of AMPK enhances your performance to such a degree that a study on mice –which where sedentary (i. e. doing nothing) and given an AMPK agonist for 4 weeks that in turn increased their running endurance by a whopping 44% and upregulated 32 genes related to oxidative metabolism– led to the banning of AMPK-activating substances in the World Anti Doping Code. On this note, I’d strongly encourage you to fast and exercise –which are both potent AMPK activators, even more potent when combined– as long as it’s still allowed.
Stay hungry – Build muscle and lose fat at the same time with intermittent fasting
Building muscle while losing fat is possible. I’d even say that it should be expected for most people following a serious program. Fasting is not mandatory for this purpose but it can serve as a faithful companion on your quest for the holy grail of body recomposition.
Although the appearance of some individuals may suggest otherwise, we’re not one big clump of uniform tissue. Muscle and fat are two different functional compartments to which calories get distributed independently. The P-ratio (partitioning-ratio) describes the lean tissue : fat tissue deposition ratio.
You can modify the receptivity of the muscle and ensure prioritization –e. g. through fasted training (GLUT4, glycogen synthase, FAT/CD36, amino acid transporters, IGF-1-receptor, local metabolic growth factors etc.).
Some people say that building muscle and losing fat on the same day is impossible because of thermodynamics. The first law of thermodynamics (the conservation of energy) is a good concept for understanding total energy and weight-balance but it’s terrible for understanding calorie partitioning –and the tissue-specific metabolic or hormonal situation for that matter.
It states that energy can neither be created nor destroyed. Energy has to go somewhere and doesn’t just disappear. An energy surplus will lead to storage and a deficit will result in energy leaving the body. You need energy to build muscle or fat cells and you release it once your break them down.
But, again, it says nothing about how the calories get partitioned.
Roughly speaking, your body needs adequate amounts of stimuli, protein, water and energy to build muscle tissue. If you supply your body with the first three things, it’ll only need energy and this energy can be gained from burning your own body fat.
You’re building muscle while losing fat.
There are limitations to this, of course. But it is absolutely possible. In general, the fatter and less muscular you are the easier it’ll be, and, vice versa, the leaner and more muscular you are the harder it’ll be.
However, there are also plenty of studies on elite athletes showing favorable changes in body recomposition (more muscle, less fat) during a caloric deficit.
In a more recent study investigating intermediate strength trainees, intermittent fasting –with a continuous caloric deficit– led to significantly greater fat loss and more hypertrophy compared to a normal diet –whose participants weren’t in a caloric deficit. (They didn’t train fasted though.)
And, mind you, fasting doesn’t per se mean being an overall caloric deficit –it puts you in an intermittent deficit. You can still (over)compensate with your subsequent meals.
To recap, the broad concept is simple:
1) Fast –> Burn fat and spare protein.
2) Train (fasted) –> Burn even more fat. Force your muscle cells to perceive stress and modify the receptivity so it’ll soak up ensuing nutrients and hormones can act optimally.
3) Eat (big) –> Prioritized shuttling of nutrients to the muscle to feed adaptive anabolic pathways. Abundant nutrients get converted to fat which will be burned in the next cycle.
4) Rest and grow
You do not have to massively overeat to build muscle. This could even lead to less muscle growth in the long term, considering the fact that a constant hypercaloric diet has been shown –among other things– to decrease insulin sensitivity, lower testosterone and cause low grade systemic inflammation, all of which will slow down, or even hinder, muscle growth to some degree. What’s more, you’ll probably get fat and sick.
Chose adequacy over excess.
Some final thoughts: Fasting will not turn you into superman and it’s not a magic bullet. The mechanisms I’ve described here, while sounding promising, probably occur at a much smaller scale than you might expect. But I still think it’s worth it.
If you have aches and pains, a bad training program, or a bad diet you have to fix that. You can not fast and neither exercise yourself out of a deep hole.
The point I want to make is that, our approach shouldn’t be a merely compensatory one. Our goals should be optimization and supercompensation.
If your diet sucks, fasting will make your diet suck less. That’s compensation.
If you eat healthy and intermittently fast your diet will get better. That’s optimization.
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