Photo by Bev Childress

Let’s take a little lactate acid 101 detour first: when your body is working out, it prefers to get its energy from aerobic activity, meaning using oxygen. But there are cases when the activity level is kind of intense, like a heavy lifting session, and your body doesn’t get enough oxygen so it switches to anaerobically generating energy. Through a process called glycolysis, muscle glycogen is metabolized into something called pyruvate. If the oxygen supply is there, pyruvate can be broken down for energy through aerobic channels. When the body lacks sufficient oxygen pyruvate goes through an anaerobic process to create more energy. The pyruvate is broken down into lactate, which enables glycolysis to continue.

Your body can for a few minutes produce a energy this way before lactate levels in the muscles increase resulting in acidity in the muscle cells. The use of lactate as fuel within the muscle itself varies with how well a person’s endurance muscle fibers are trained aerobically. Lactate can also be sent to the brain and heart for fuel, or to the liver to be converted to glucose, or move to active and inactive muscles and used as energy.

We know the value of lactic acid today, but it is still misunderstood, and in the past, it was even viewed as a muscle poison. We have George Brooks, a professor of integrative biology at the University of California, Berkeley, for helping to change our understanding of lactate. When Brooks first began investigating lactic acid sports physiologists saw it as a muscle poison that lowered performance. His research over decades has reversed that picture, showing that it is the body’s way of revving up for exercise or to fight disease. Clinicians are now planning clinical trials to use lactate to treat traumatic brain injury and a host of illnesses, including heart attacks, inflammation and swelling.

Starting in the 1970s, Brooks, his students, postdoctoral fellows and staff were the first to show that lactate wasn’t waste. It was a fuel produced by muscle cells all the time and often the preferred source of energy in the body: The brain and heart both run more efficiently and more strongly when fueled by lactate than by glucose, another fuel that circulates through the blood.

“It’s a historic mistake,” Brooks said. “It was thought that lactate is made in muscles when there is not enough oxygen. It has been thought to be a fatigue agent, a metabolic waste product, a metabolic poison. But the classic mistake was to note that when a cell was under stress, there was a lot of lactate, then blame it on lactate. The proper interpretation is that lactate production is a strain response, it’s there to compensate for metabolic stress. It is the way cells push back on deficits in metabolism.”

Gradually, physiologists, nutritionists, clinicians and sports medicine practitioners are beginning to realize that high lactate levels seen in the blood during illness or after injury, such as severe head trauma, are not a problem to get rid of, but, in contrast, a key part of the body’s repair process that needs to be bolstered.

“After injury, adrenaline will activate the sympathetic nervous system and that will give rise to lactate production,” Brooks said. “It is like gassing up the car before a race.”

Without this added fuel, the body wouldn’t have enough energy to repair itself, and Brooks says that studies suggest that lactate supplementation during illness or after injury could speed recovery. Over the course of decades of research, Brooks has discovered that there are at least three main uses of lactate in the body: It’s a major fuel source, it’s the major material to support blood sugar level and it’s a powerful signal for metabolic adaptation to stress. In a recent article in the journal Cell Metabolism¹, Brooks reviews the history of lactic acid.

“The reason I wrote the review is that people in all these different disciplines are seeing different effects of lactate, and I am pulling it all together,” said Brooks. “Lactate formulations have been used for decades to fuel athletes during prolonged exertions; it’s been used widely for resuscitation after injury and to treat acidosis. Now, in clinical experiments and trials, lactate is being used to help control blood sugar after injury, to fuel the brain after brain injury, to treat inflammation and swelling, for resuscitation in pancreatitis, hepatitis and dengue infection, to fuel the heart after myocardial infarction and to manage sepsis.”

Brooks’s research has already benefitted endurance athletes. In 1989, he worked with a sports firm to create an energy drink called Cytomax that includes a lactate polymer that can give athletes an energy boost before and during competition. A combination of lactate, glucose, and fructose, it takes advantage of the different ways the body uses fuel: lactate can get into the blood twice as fast as glucose – peaking in just 15 compared to 30 minutes after drinking. Most sports drinks contain only glucose and fructose.

Lactate Shuttle

We all store energy in several forms: as glycogen, made from carbohydrates in the diet and stored in the muscles; and as fatty acids, in the form of triglycerides, stored in adipose tissue. When energy is needed, the body breaks down glycogen into lactate and glucose and adipose fat into fatty acids, all of which are distributed throughout the body through the bloodstream as general fuel. However, Brooks said, he and his lab colleagues have shown that lactate is the major fuel source.

Glucose and glycogen are metabolized through a complex series of steps that culminate in lactate. For almost a century, scientists and clinicians believed that lactate is only made when cells lack oxygen. However, using isotope tracers, first in lab animals and then in people, Brooks found that we make and use lactate all the time.

This is what he calls the lactate shuttle, where “producer” cells make lactate and the lactate is used by “consumer” cells. In muscle tissue, for example, the white, or “fast twitch,” muscle cells convert glycogen and glucose into lactate and excrete it as fuel for neighboring red, or “slow twitch,” muscle cells, where lactate is burned in the mitochondrial reticulum to produce the energy molecule ATP that powers muscle fibers. Brooks was the first to show that the mitochondria are an interconnected network of tubes – a reticulum – like a plumbing system that reaches throughout the cell cytoplasm.

The lactate shuttle is also at work as working muscles release lactate that then fuels the beating heart and improves executive function in the brain.

In discovering the lactate shuttle and mitochondrial reticulum, Brooks and his UC Berkeley colleagues have revolutionized thinking about metabolic regulation in the body; not just in the body under stress, but all the time.

For decades scientists and clinicians believed that in cells, glycogen and glucose are degraded to the lactate precursor substance called pyruvate. That turned out to be wrong, since pyruvate is always converted to lactate, and in most cells lactate rapidly enters the mitochondrial reticulum and is burned. Working with lactate tracers, isolated mitochondria, cells, tissues and intact organisms, including humans, Brooks and UC colleagues discovered what had been missed and, consequently, misinterpreted. More recently, others have used magnetic resonance spectroscopy (MRS) to confirm that lactate is continuously formed in muscles and other tissues under fully aerobic (oxygenated) conditions.

Brooks notes that lactate can be a problem if not used. Conditioning in sports is all about getting the body to produce a larger mitochondrial reticulum in cells to use the lactate and thus perform better.

Tellingly, when lactate is around, as, during intense activity, the muscle mitochondria burn it preferentially and even shut out glucose and fatty acid fuels. Brooks used tracers to show that both the heart muscle and the brain prefer lactate to glucose as fuel, and run more strongly on lactate. Lactate also signals fat tissue to stop breaking down fat for fuel.

“One of the important things about lactate is that it gets into the circulation and participates in inter-organ communication,” said Jen-Chywan “Wally” Wang, a UC Berkeley professor of nutritional sciences and toxicology. “Which is why it’s very important in normal metabolism and an integral part of whole-body homeostasis.”

Lactate is the Body’s VISA

In his review, Brooks emphasizes three major roles for lactate in the body: It’s a major source of energy; a precursor for making more glucose in the liver, which helps support blood sugar; and a signaling molecule, circulating in the body and blood and communicating with different tissues, such as adipose tissue, and affecting the expression of genes responsible for managing stress.

For example, studies have shown that lactate increases the production of Brain-Derived Neurotropic Factor (BDNF), which in turn, supports neuron production in the brain. And, as a fuel source, lactate immediately improves the brain’s executive function, whether lactate is infused or comes from exercise.

“It’s like the VISA of energetics; lactate is accepted by consumer cells everywhere it goes,” he said.

The fact that lactate is an all-purpose fuel makes it a problem in cancer, however, and some scientists are looking for ways to block the lactate shuttles in cancer cells to cut off their energy supplies.

“Recognition that lactate shuttles among producer and consumer cells in tumors offers the exciting possibility of reducing carcinogenesis and tumor size by blocking producer and recipient arms of lactate shuttles within and among tumor cells,” he wrote in his review.

All this presages a turnaround in the appreciation of lactate, though Brooks admits that textbooks – except for his own, Exercise Physiology: Human Bioenergetics and Its Applications, now in its fourth edition – still portray lactate as a bad actor.

“Lactate is the key to what is happening with metabolism,” Brooks said. “That is the revolution.”

Reference

1. Brooks, George A. “The Science and Translation of Lactate Shuttle Theory.” Cell Metabolism 27, no. 4 (April 3, 2018): 757–85.

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For many in this situation, the answer lies in a better understanding of their metabolism. Indeed, while trending training routines and dietary plans may work for some, they are usually extremely generic in the sense that they target only those people with a specific metabolic configuration. Naturally, they will not advertise this fact in headline font. In fact, they will commonly omit it altogether. So you pick up a popular set of reps and you religiously follow through with it. You eat a champion’s breakfast and concoct a nutrition-bomb smoothie before and after your workout sessions. You count every calorie you ingest. You do this for several weeks and, when you notice no progress, you understandably feel like throwing in the towel.

What I’m here to say, though, is that all hope is not lost.

Yes, training and physical exercise, together with a healthy diet, are essential for any increase in physical performance. However, metabolism is, in this case, the single most important process taking place in your body. Knowing your metabolism, therefore, is key to achieving more through your workout, regardless of whether you’re building muscle, training for a marathon or just staying fit. Following are the basics.

Metabolism and Physical Performance

Metabolism is so closely connected with both muscle growth and physical performance that they are virtually synonymous. In short, metabolism represents the sum of all chemical reactions taking place throughout the body, at a cellular level, for the purpose of providing energy and synthesizing new organic material. In the absence of metabolic processes, the body has no energy to sustain vital functions, let alone sustain physical activity. Furthermore, without metabolic processes, the synthesis of muscle tissue does not take place.¹ It really is this simple.

But it does get more complicated from here. The human body relies on three main macronutrients for energy, and these are fat, protein, and carbohydrates. Of these, carbohydrates represent the body’s favorite source of fuel, which is to say that the body first turns to carbs in order to meet its energy needs. Once ingested, carbohydrates are broken down into basic components, such as glucose, galactose, and fructose. Glucose can be used as a fuel source for the brain and muscle tissue immediately, whereas the remaining two must first be metabolized into glucose by the liver. When sufficient carbs are ingested to create an excess of energy, the energy is stored as glycogen. If glycogen stores are also full, excess glucose is oxidized and stored as fat.

So what exactly happens when you work out? During physical exercise, the body first calls on any glucose present in the bloodstream for energy. In sessions that last more than one or two hours, glucose is depleted and the body begins to use up its stores of glycogen. At most, however, the latter will provide the equivalent of 2000 calories, so what happens when glycogen is also depleted? This is the moment when the body shifts towards protein catabolism to sustain continued effort. In other words, it begins to break down muscle tissue for amino acids, which are, in turn, oxidized for fuel. Protein is directed away from its primary task, building muscle and connective tissue, and the long-term result is the loss of muscle mass. Obviously, this is bad.

Derived from this are two basic principles that you can take into account when analyzing the relation between your metabolism and physical performance:

1. If your intake of carbohydrates is poor or insufficient and your body is not properly stacked on glycogen, protein catabolism will likely occur during extensive workout sessions.² You may think and feel that you’re exhausting yourself each time, and your routine may be an excellent one for muscle growth, but the results will ultimately disappoint you. Not only will your body lack the necessary resources to build new muscle, but it will actually be forced to break down some of the existing muscle tissue in order to meet its own energy needs.
2. In order to increase your lean body mass, your body requires protein, of course, but it also requires more energy than your daily energy expenditure.³ The latter varies greatly from person to person, and is derived from the sum of your resting metabolic rate (RMR or the energy your body consumes while idle, for vital functions) and your exercise energy expenditure. Once you have assessed both and calculated your 24-hour energy expenditure, you can devise a nutritional plan that either matches the total amount, if you are training for an endurance event, or that exceeds the total amount, if you intend to increase lean body mass.

For each metabolism, there are both exercise and dietary requirements that, when fulfilled, can help an athlete achieve better performances. For the purpose of this discussion, I will focus only on the relationship between diet, different metabolic rates, and physical performance. To see the above principles in action, we will first look at an average metabolic rate, followed by a slow metabolic rate and, finally, by a fast metabolism. In each case, I will also present several suggestions for an appropriate, performance-enhancing nutritional plan.

Nutritional Needs for the Average Metabolism

Once you’ve completed your metabolic assessment at a nearby clinic, a specialist will be able to indicate whether your metabolic rate or, more likely, your resting metabolic rate falls within average parameters. If so, that is great news. Most workout routines and diets should show results in your case, but even so, you should be aware of some general principles of nutrition, metabolism and performance.

Broadly speaking, in order to achieve optimal results from your workouts, your nutrition should include⁴:

Complex Carbohydrates

Carbs that rank low on the GI (glycemic index) and will provide you with sustained energy, rather than a quick burst. Your aim, as an active individual with an average RMR, is to consume 40% of your total calorie intake as carbohydrates. Some examples include raw fruits and vegetables, whole-wheat breads, and high-fiber cereals.

Protein

An absolutely essential component for repairing and building muscle tissue. Your goal is to consume an average of 30% of your total calorie intake as protein. Some examples include turkey, chicken breast, and salmon or, for vegans and vegetarians, seitan products, tofu, lentils, chickpeas, and most varieties of beans.

Good Fats

Intake mono and poly-unsaturated fats, as opposed to saturated and trans fats. Ideally, you should consume an average of 20-30% of your total calorie intake as fats. Some examples of foods containing good fats are vegetable oils (olive or canola, for instance), a variety of nuts (almonds, peanuts, cashews), avocados, and peanut butter.

Plenty of Water

The importance of water cannot be overstated. Intensive workouts, unusual heat, and fluid loss through sweat all deplete the body of water. Without water, a number of vital functions can no longer be fulfilled correctly, which translates into inefficient training and a lesser athletic performance. Under normal circumstances, it is recommended that an adult drinks at least 8 glasses of water per day (about 2 liters). In addition to this, consider drinking 0.5 liters (2-3 glasses) one or two hours prior to your workout, as well as at least another 0.5 liters during workout.

Another thing to consider is the timing of your meals in relation to your workout sessions. Ideally, this involves three meals, one before, one during, and one post-workout, each with different roles in enhancing your performance.

Your pre-workout meal (2-3 hours prior) is designed to provide energy for your body, hydrate you, and help you preserve muscle mass. In other words, you’re looking to include a moderate amount of protein, a good handful of your favorite complex carb food, and a small amount of fat.

Your during-workout meal needs to keep you hydrated, provide your body with substances that can be used for immediate fuel, and help you prevent muscle loss. For obvious reasons, this meal is best served as a drink, which should include, per hour of exercise, 15 grams of protein and 30-45 grams of carbs, avoiding fat altogether. A good idea is to prepare a during-workout smoothie, using half a scoop of protein powder and your preferred source of carbs (ranging from sports drinks to bananas, oats, quinoa, blueberries, beetroot, or even beans). Don’t forget to also drink enough water in addition to consuming your shake.

Your post-workout meal (0-2 hours after) is meant to help you recover, rehydrate, and build muscle mass. As such, it should include a good amount of protein, a moderate amount of carbs, and a small amount of fat. Although some prefer to prepare a post-workout shake that they can consume immediately after exercise, it is debatable whether or not this is actually necessary. In fact, so long as you eat your meal no longer than two hours post-workout, this should prevent any unwanted muscle breakdown.

Bear in mind that all the figures above are essentially designed to support an average resting metabolic rate, as well as an average workout routine. Athletes and bodybuilders have somewhat different nutritional needs and require further personalized dietary plans. An endurance athlete, for instance, has much higher calorie and carbohydrates needs, while a bodybuilder requires additional protein in order to facilitate major muscle growth.

And what about those with metabolic rates that fall below or above the average? Read on.

If Your Metabolism Is Slow

If your metabolic rate was assessed below average, it’s important for you to understand that this is not necessarily bad news. In fact, metabolic rate alone is never the culprit for weight gain, and it certainly doesn’t represent an obstacle in terms of physical performance.5 Rather, it simply means that your body uses up fewer calories in order to maintain vital functions. Having this awareness and knowing exactly how much you need to eat is all you need to keep unwanted weight gain at bay and to become, or stay, fit.

In terms of what your nutrition should include, as well as your three workout meals, you must bear in mind that your body finds it more difficult to process carbs and that, in addition to this, you have lesser energy needs. Of course, if you’re looking to build muscle mass or increase endurance, you too will need to consume more calories than your total 24-hour energy expenditure, but unlike other metabolic types, you should only exceed the latter by a small amount.

More specifically, it’s a good idea to lower your intake of carbs to about 25% of your total calorie consumption and to eat most of your carbs after working out. In your case, it is all the more important to consume complex carbs that do not immediately spike your blood sugar, since, due to your slow metabolism, you are prone to a poor insulin sensitivity.

You’ll want to up your protein intake to about 35% of total calorie consumption, which you can distribute evenly throughout the three meals. This is important not only because protein is the building block for muscle tissue, but also due to its ability to temporarily boost the metabolism.

Don’t be afraid of fat, so long as it comes in mono and poly-unsaturated types. People with slow metabolic rates showed best results on a high protein and fat diet, so up your fat intake to about 30-40% of your total calorie consumption.

Finally, there are a few nutritional tricks you might consider in terms of speeding up your metabolism. For instance, did you know that water has been shown to temporarily increase metabolism by 24-30%? This is partly due to the fact that calories are immediately used in order to heat the water to body temperature. Drinking enough water is a great way to stay hydrated in the first place, and this makes it even better for those with lagging metabolisms. Coconut oil, cocoa, as well as tea and coffee in moderate amounts have also displayed metabolism-boosting properties.

Metabolism on the Fast Track to Nowhere?

Most people tend to think that a fast metabolism is a free ticket to a life without fitness-related worries. While it is true that, if your metabolic rate was assessed above average, you naturally consume more calories in a day and you rarely put on weight, this fact is a double-edged sword. Gaining muscle mass is precisely that—putting on a specific type of weight, and it can be difficult to do with a fast metabolism.⁶ Nevertheless, this is not an impossible task. As usual, it begins with a metabolic assessment and the knowledge of exactly how many calories your body uses per day for vital functions, as well as for physical effort.

The trick, in terms of your nutrition plan, is to eat well above your total 24-hour energy expenditure. In addition, since your body can easily manage carbohydrates, while carbs, in turn, can help you build up your energy reserves, these should take up the better part of your meals. As such, your carbs intake should measure up to 55% of your total calorie consumption.

When it comes to protein, a moderate 25% of your total calorie consumption is ideal. Of course, if your focus is to significantly accelerate muscle growth, you can and should increase your protein consumption to 30-35%.

As always, healthy fat is not something to be ignored in a comprehensive diet. Nevertheless, if your metabolism is fast, you’ll want to keep your fat intake low, at about 20% of your total calorie intake.

Finally, pre, during, and post-workout meals are all the more essential for you, especially when it comes to your carbohydrate consumption. Remember that if your body cannot support its own energy requirements with glucose and glycogen, it will resort to breaking down muscle tissue for protein. Since you are prone to consuming lots of energy, you are particularly vulnerable to protein catabolism. In fact, it may be the reason why you haven’t noticed any improvements in your muscle mass in spite of working out consistently.

As the possessor of a quick metabolic rate, you’ll soon notice that muscle growth and especially endurance training require you to do a lot of eating. In fact, it is generally recommended that you eat as many as five meals per day, which may, at first, seem daunting. You’ll also have to be extra-diligent with your gym sessions, as building muscle will require you to train with weights intensely and consistently. On the other hand, there is, of course, the bright side, for when others will be terrified of carbohydrate-dense foods, you will casually produce a cookie from your bag, eat it with satisfaction, and then return to your multi-joint compound mass building reps.

The Ultimate Takeaway

There is an indisputable link between your metabolism and your physical performance, which you may be able to mediate through an appropriate nutritional plan. If you have struggled to increase your muscle mass, lose weight, or improve your endurance in spite of eating “right” and working out consistently, then metabolism might be the answer to your problem. There is only one way to find out, and that is undergoing a metabolic assessment at a nearby clinic or gym.

As you’ll notice while further researching the process, there are a number of online calculators that claim to be able to produce your RMR or your 24-hour energy expenditure with only a few details about your body. The issue with these, however, is that, like trending workout routines and dietary plans, they are designed with the average metabolic rate and body type in mind. Chances are, the results will not apply to your particular situation, which is why, if you’re serious about increasing your athletic performance, you should find out your RMR from a reliable source.

With the metabolic assessment out of the way, you’ll be able to tailor both your workout routines and your nutrition to fit your personal needs for much more effective training.

References:

1. Hans Kornberg, “Metabolism,” Encyclopaedia Britannica, 22 November 2017, accessed January 26, 2018.

2. Michael J. Rennie and Kevin D. Tipton, “Protein and Amino Acid Metabolism during and after Exercise abd the Effects of Nutrition“, Annual Review of Nutrition, vol. 20 (2000), accessed January 26, 2018.

3. NSCA Kinetic Select, “Sport Performance and Metabolic Rate“, National Strength and Conditioning Association, 2015, accessed January 25, 2018.

4. American Dietetic Association, “American College of Sports Medicine position stand. Nutrition and athletic performance“. Medicine and Science in Sports and Exercise, vol. 31, no. 3 (2009), accessed January 25, 2018.

5. Harvard Medical School, “Does Metabolism Matter in Weight Loss?” Harvard Health Publishing, July 2015, accessed January 26, 2018.

6. K. D. Tipton and R. R. Wolfe, “Exercise, protein metabolism, and muscle growth“, International Journal of Sport Nutrition and Exercise Metabolism, vol. 11, no. 1 (2001), accessed January 26, 2018.

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