I could write an entire book on nutrient timing as it relates to exercise. In fact, I actually read a book called Nutrient Timing System enough times in my early nutrition coaching career that I decided to create a Cliffs Notes™-style summary of the book by Dr. Robert Portman & John Ivy. To receive a free copy of this summary, enter your email above (don’t forget to download it)!

Nutrient Timing System was a great resource because it is research-based and breaks down nutrient timing for exercise into a simple formula. Since its publishing, many fitness professionals have made nutrient timing recommendations based on the scientific literature that the book was based on, and I have seen many nutrition articles echo its prescriptions.

The core idea behind nutrient timing is that there are specific energy needs of the body at certain times of day. The book, Nutrient Timing System, looks specifically at your nutrition needs before, during and after exercise.

If you can match your dietary nutrition to your body’s needs throughout the training cycle, you will optimize your recovery and performance gains. If you do not match your dietary nutrition to the body’s needs, you can actually stall your gains and experience adverse occurrences such as net muscle protein breakdown (put simply, muscle loss).

Nutrient timing research promises a lot. The literature throws a lot of big percentages at you, 400% increases here, 80% reductions there. At times it seems like the holy grail of nutritional interventions. It is, in fact, a very important concept for people who exercise regularly to understand, but it is not a silver bullet.

If your nutrition as a whole is off, nutrient timing strategies will not be as effective. If you have hormonal issues such as insulin resistance, nutrient timing strategies will not be as effective. However, if you are already healthy, eating well, and training frequently nutrient timing is probably the best strategy you can implement to accelerate your progress!

A DIFFERENT PERSPECTIVE

Most articles on nutrient timing will be polarized. Some will say its snake oil and doesn’t work at all, others will put it on a pedestal. I, however, believe that its’ effectiveness is highly contingent on each individual, their training program, and current biochemistry.

Articles that sound dogmatic about their nutrient timing recommendations, and seem credible because they cite scientific research should be taken with a grain of salt.

A 2013 meta-study on nutrient timing took a look recent studies related to post-exercise nutrient timing and its effect on subjects who engaged in resistance training (weight lifting). The study, titled “Nutrient Timing revisited: is there a post-exercise anabolic window?”, and the book, Nutrient Timing System, look at “apples and oranges” research that was performed with a variety of different testing methods.

Some studies had test subjects who were untrained, in others they were trained triathletes or bodybuilders. In some studies the subjects were young, in others they were elderly. In some they cycled, others they ran, and in others they performed various types of resistance exercise. Some studies used high-quality protein sources, others lower quality. They all used varying combinations of nutrients, and different times.

As you can see, to draw any firm conclusions from reviewing this literature is difficult because of the differences in testing conditions. To derive broad recommendations for all modalities of exercise from the results of these studies is even more difficult.

The authors of Nutrient Timing revisited put it well in the introduction to the practical applications section of the review:

“Distilling the data into firm, specific recommendations is difficult due to the inconsistency of findings and scarcity of systematic investigations seeking to optimize pre and/or post-exercise protein dosage and timing. Practical nutrient timing applications for the goal of muscle hypertrophy inevitably must be tempered with field observations and experience in order to bridge gaps in the scientific literature.”

Don’t let these words of caution scare you away from nutrient timing strategies as a whole. There are well observed strategies from the “field”, and lessons that everybody can take from these studies.

This article is meant to give you some context for the information that you will encounter in the media, or hear from your bro at your gym who loves to give out free nutrition advice. It will also provide strategies based on your individual goals and needs.

NUTRIENT TIMING BACKGROUND

In my last article we explored metabolism, but we only covered one part of the equation. We looked at the different “catabolic” metabolic pathways, the chemical reactions that occur to break down our body’s stores of energy and regenerate ATP for movement. We also have an “anabolic” metabolism which rebuilds what the catabolic metabolism has broken down.

In the article on metabolism, we also explored ways to “feed” each metabolic pathway for optimal function. This knowledge is important to understanding the goals of nutrient timing, and we will build on it today.

It is also important to understand that after we are done training our anabolic metabolism is hard at work building up our body’s energy stores where the catabolic metabolism broke them down, and there are important strategies to fueling anabolism as well which we will explore later.

anabolic vs. catabolic anabolism vs. catabolism
Source: allmaxnutrition.com

During exercise, there are a few catabolic hormones that are coursing through our veins as we begin and sustain exercise.

Epinepherine/Norepinephrine (also known as adrenaline/noradrenaline) increase blood flow to the muscles. During exercise, muscle blood flow increases fivefold over resting rates, hence the term “adrenaline rush”. Adrenaline also helps stimulate fat and glycogen breakdown as our blood sugar drops in response when we initiate exercise.

Cortisol is also released in response to exercise and low blood sugar and helps break down stored fat, glycogen, and muscle protein for energy. Cortisol levels determine the degree of muscle breakdown, and for this reason we want to keep our cortisol levels in check during exercise.

The catabolic hormones that are released during exercise to break down our tissues for the purpose of energy regeneration to fuel muscle contraction actually stay elevated during the post-exercise period. Our goal with post-workout nutrition is to stimulate the release of anabolic hormones to stop muscle damage and help the body begin rebuilding tissue. This includes rebuilding our stores of energy such as glycogen and the synthesis of proteins for muscle repair.

The main anabolic hormone we want to stimulate post-exercise is insulin! I have mentioned before that elevated insulin is one of the conditions for fat storage, but in the post-exercise period we actually want to elevate insulin through diet for a few reasons:

  • It increases muscle blood flow which helps clear metabolic waste allowing cells to regenerate creatine phosphate and glycogen
  • Suppresses cortisol to stop breakdown of muscle
  • Tissue repair is initiated

The muscles are most insulin sensitive during the 45 minute period following exercise. At about 4 hours the muscles start to become insulin resistant. Insulin is released in response to elevated blood glucose, but also in response to protein.

Now we will look at what the relevant research shows about the effect of nutritional interventions before, during, and after exercise.

WHAT DO WE NEED BEFORE AND DURING EXERCISE?

In the article on metabolism, we learned the different ways that the body regenerates ATP during exercise on a cellular level.

First, it relies on ATP stores in the cell, once they are depleted phosphocreatine kicks in for about 10 seconds, we begin to rely on stored carbohydrate called “glycogen” as the intensity stays high, and when we are exercising at low intensity or resting between intervals oxygen helps us regenerate energy from fat, carbohydrate, and protein.

We talked about how you can feed the different metabolic pathways with supplementation and food, but did not discuss the role of intra-workout supplementation (or supplementation during exercise).

The goal of intra-workout supplementation is to improve the delivery of energy regenerating nutrients to the muscles, spare muscle glycogen, and minimize the muscle protein breakdown (BCAAs and glutamine are most depleted amino acids) associated with elevated cortisol levels during exercise.

Research has shown that a diluted carbohydrate and protein drink consumed during exercise has a significant reduction of glycogen depletion and cortisol suppression.

One study showed that a 6% carbohydrate solution had an 80% reduction in cortisol levels vs. water. What does a 6% carbohydrate solution look like in practical terms? Fifteen grams of carbohydrate per cup (8oz) of water.

When reviewing the original study, I found that the study looked at 10 trained triathletes completing a glycogen-depleting 2.5 hour run and a 2.5 hour cycling exercise in separate sessions while consuming either a placebo or 6% carbohydrate solution every 15 minutes.

Sounds like everybody should be sipping a carbohydrate solution during training if cortisol management is the goal, doesn’t it? Unfortunately, unless you are a triathlete completing a 2.5 hour relatively steady-state mode of exercise at a high intensity this science does not perfectly translate to you.

I would contend that for your average person, even CrossFit athletes, who are just looking to get fit or shed a few pounds of body fat there is no need to worry about intra-workout carbohydrate supplementation whatsoever. For that reason, there is no need for you to go out and buy a maltodextrin supplement, carefully weigh out 15 grams per cup of water and strategically consume it during a 10 minute Metcon.

I would, however, suggest experimenting with a BCAA and glutamine mix during workouts to spare muscle breakdown for all athletes.

On the other hand, for a competitive fitness athlete training for multiple hours per day who is focused on performance or mass gains you can experiment with a 6% carbohydrate solution mixed with some BCAA and glutamine during your 2-3 hour exercise period to keep cortisol low, spare muscle tissue, and preserve glycogen stores so that you can continue to push yourself anaerobically.

POSTWORKOUT NUTRITION: THE “ANABOLIC WINDOW”

After exercise, our muscles are hungry. They just spent the last hour or so working hard to break down big complex molecules such as glycogen to generate a simple form of energy, ATP. In the process, free radicals such as hydrogen ions and a host of other metabolic waste products have been created and need to be removed from the cell before causing too much damage.

Studies have also shown that even 3 sets to failure of bicep curls can deplete 24% of glycogen in the muscle. Kick it up to 6 sets at a lower weight and we see a 38% decrease in glycogen storage.

Our muscles NEED blood flow in order to deliver nutrients, especially carbohydrate in the form of glucose, for glycogen repletion and to clear the damaging metabolic wastes created during catabolism. The hormone insulin is the key to kickstarting these anabolic processes.

metabolic-window

The increased blood flow to the muscles that insulin stimulates allows our muscle cells to replete glycogen, phosphocreatine stores, and begin removing metabolic wastes. After exercise, our muscle cells become more insulin “sensitive” and have an enhanced ability to transport glucose from the blood into the cells to manufacture and store glycogen.

So how do we stimulate the release of insulin after exercise to kickstart these processes? Both carbohydrate intake and protein intake are adequate in isolation, but even more potent in combination.

Studies on nutrient timing have shown that consuming a protein + carbohydrate beverage immediately post-exercise rapidly increases the rate and total volume of glycogen repletion vs. the same beverage consumed 2 hours later.

Various studies also show that a carb and protein beverage immediately AND a few hours post workout are effective in increasing muscle protein synthesis, glycogen replenishment, reducing muscle damage, and reducing immune system suppression that results from exercise.

That is the science of nutrient timing post-workout. The art of nutrient timing revolves around determining what to eat or drink after exercise, how much to consume, and how to make it convenient to consume it as immediately as possible.

Because whole food sources are unpalatable for a considerable period of time post-exercise, powdered supplements mixed with liquid are a popular option. They are also popular because of their convenience.

It is harder to eat a mixed meal consisting of meat and potatoes after an intense CrossFit metcon than it is to drink a 16oz. protein and carb shake. It is also hard to bring the mixed meal with you to the gym, especially if you spent the day at the office first.

By supplementing your whole food diet with liquid nutrition post-exercise, you can set the stage for optimal recovery and give yourself the opportunity to cool down from your workout, get home, heat and eat a whole food meal.

But how much protein and carbohydrate should you consume post-exercise? I don’t like to rely on the science for these recommendations. CrossFit has a high degree of variety in the intensity and duration of each workout. Every day, your needs will be slightly different.

THE ANABOLIC WINDOW AFTER STRENGTH TRAINING

To find some applicable recommendations, we will first look at the results of nutrient timing research performed on subjects who engaged in resistance exercise. These studies look at both trained and untrained subjects engaging in isolation movements like leg extensions, bicep curls etc. as well as functional compound movements like squats, bench press, deadlift and leg press.

The research done on athletes who performed an exercise program consisting of functional movements (squat, bench, deadlift) will be more relevant to strength athletes, CrossFit athletes, and anybody engaging in high intensity weight lifting so we will focus on this subset of the literature.

Some of the studies that fit these criteria have found that a protein supplement consumed both pre and post workout has an effect on improving total muscle mass and 1 rep max strength, while others showed no significant difference between immediate consumption and later consumption.

One study did, however, look at the effect of a protein/carbohydrate/creatine blend consumed pre and post workout. This study showed a significant improvement in muscle mass and 1 rep max strength after 10 weeks in the group consuming the blend immediately pre and post workout vs. the group consuming the same blend in the morning and at night.

If your goals are to add muscle mass (which also positively effects fat loss) or to improve your athletic performance, these findings are both important and relevant to you. Experiment with consuming a carb/protein/creatine mix before and after exercise for a microcycle of training (about 8-10 weeks) and observe whether your rate of improvement is greater than a previous baseline.

The research had subjects consuming about .45g of carb and protein combined per pound of bodyweight with 7g of creatine pre and post workout. For a 175lb male this translates to about 40g each of protein and carbohydrate with 5g of creatine pre and post workout.

THE ANABOLIC WINDOW AFTER METABOLIC CONDITIONING

I am still waiting on research that will translate to how to fuel yourself after a high intensity, mixed modality (resistance exercise and ‘cardio’) training session such as a CrossFit metcon.

The research that looks at the effect of post-exercise nutrition on athletes who completed high-intensity cycling workouts (most of the studies in the book Nutrient Timing System) are not the best analogs for CrossFit, strength training, or other high-intensity and shorter duration forms of exercise.

For knowledge about fueling ourselves after a CrossFit metcon or interval workout, we need to rely on field experience in addition to recommendations such as 0.5g of carbohydrate per pound of bodyweight post-exercise seen in a University of Texas study on cyclists completing 2-hour high intensity sessions.

From my experience, I recommend that weekend-warrior fitness athletes who attend high intensity group classes 3-5 days per week for an hour focus on getting liquid protein supplementation post-exercise and whole food carbohydrate sources within 1-hour.

Don’t worry about carbohydrate supplementation. Instead, focus on shifting your day’s starch intake (potato, rice, grains) to the 1-4 hours post-workout when your muscles are insulin sensitive, and avoid starches outside that window.

For competitive fitness athletes training multiple sessions per day or 10+ hours per week, you will benefit from liquid carbohydrate supplementation both during and after exercise. I recommend about 40g of carbohydrate mixed with protein post-exercise, and based on the research it appears effective to drink this blend pre-workout as well.

If you are planning to do multiple training sessions in the same day, make sure to absolutely gorge yourself with carbohydrates after your first training session to ensure proper glycogen repletion. Studies have looked at the effects of training in a glycogen depleted vs. glycogen repleted state and have found that when training in a depleted state athletes experienced double the nitrogen loss (nitrogen loss is an indication of muscle breakdown).

POST WORKOUT NUTRITION: AFTER THE ANABOLIC WINDOW

If you consume a liquid supplement and/or a mixed meal consisting of starchy carbohydrate and protein, insulin will stay elevated and extend the anabolic window out to about 4-6 hours post-exercise. After 4-6 hours, anabolic activity continues, but at a slower rate.

At this point, our goal is simply to ensure that we are consuming enough total calories and macronutrients to replenish what we have broken down during exercise, and support lean muscle mass.

Your first goal outside of the anabolic window is to ensure you eat enough total protein to fuel muscle protein synthesis and avoid muscle protein catabolism. As discussed in previous articles, the research shows that about .82g of protein per pound of bodyweight per day is adequate.

Next, if your goal is to maintain weight, gain muscle mass, or generally improve athletic performance you want to make sure you are consuming enough total calories to maintain a neutral or positive energy balance. This means eating enough to match or exceed your caloric expenditure.

Research shows that protein synthesis continues for up to 48 hours post-workout. For this reason, consuming more vs. less protein is key to supporting muscle gains. There has also been research done which shows a positive energy balance, eating more than you burn, leads to greater gains in muscle mass.

SUMMARY

For those of you concerned with fat loss, not performance or mass gain, the most important insights from nutrient timing that you can put into action are:

  • Only eat starchy carbohydrates (potato, sweet potato, rice, plantian/banana, grains) and sugars (refined or from fruit) during the anabolic window when they can be used by the muscle.
  • Consume a liquid protein beverage post-exercise to help stimulate insulin until you can eat a whole food meal containing starchy carbohydrates.
  • Outside of the anabolic window, make sure to consume enough protein and keep carbohydrate intake low sticking to complex carbohydrate sources that contain fiber, such as vegetables.

For performance-oriented athletes and those interested in mass gain, the following are recommendations to experiment with:

  • Drink a protein/carbohydrate/creatine beverage immediately pre and post workout
  • Sip a 6% carbohydrate solution mixed with BCAA and glutamine (about 5-10g) during your workout.
  • If training twice in one day, increase your carbohydrate intake after the first training session.
  • Liquid supplementation pre/intra/post-workout is conducive of muscle anabolism and will reduce muscle protein breakdown. Mixed meals every 1-2 hours post-workout extends the anabolic window.
  • Eat a caloric surplus

Nutrient timing is neither snake oil nor a silver bullet. It does, however, provide some great nutritional strategies with which to experiment. Give some of these recommendations a go and see if they work for you. To dig deeper into the science of nutrient timing, I highly recommend reading my summary of Nutrient Timing System, read the book, and check out the resources below to draw your own conclusions from the studies I used to create this article.

SOURCES

  1. Ivy, John, and Robert Portman. Nutrient Timing System: The Revolutionary New System That Adds the Missing Dimension to Sports Nutrition: The Dimension of Time. North Bergen, NJ: Basic Health Publications, 2004. Print.
  2. Aragon, Alan Albert, and Brad Jon Schoenfeld. “Nutrient Timing Revisited: Is There a Post-exercise Anabolic Window?” J Int Soc Sports Nutr Journal of the International Society of Sports Nutrition 10.1 (2013): 5. Web. <http://www.biomedcentral.com/content/pdf/1550-2783-10-5.pdf>.
  3. Cribb, Paul J., and Alan Hayes. “Effects of Supplement Timing and Resistance Exercise on Skeletal Muscle Hypertrophy.” Medicine & Science in Sports & Exercise 38.11 (2006): 1918-925. Web. <https://www.purdue.edu/swo/nutrition/KnowItAll/HealthyWeightGain/EffectOfSupplTiming&ResistanceExcerciseOfSkeletalMuscleHypertrophy.pdf>.
  4. Hulmi, Juha J., Vuokko Kovanen, Harri Selänne, William J. Kraemer, Keijo Häkkinen, and Antti A. Mero. “Acute and Long-term Effects of Resistance Exercise with or without Protein Ingestion on Muscle Hypertrophy and Gene Expression.” Amino Acids 37.2 (2008): 297-308. Web. <http://www.ncbi.nlm.nih.gov/pubmed/18661258>.
  5. Hoffman, Jay R., Nicholas A. Ratamess, Christopher P. Tranchina, Stefanie L. Rashti, Jie Kang, and Avery D. Faigenbaum. “Effect Of Protein Supplement Timing On Strength, Power And Body Compositional Changes In Resistance-trained Men.” Medicine & Science in Sports & Exercise 41.Supplement 1 (2009): 303. Web. <http://www.ncbi.nlm.nih.gov/pubmed/19478342>.
  6. Willoughby, D. S., J. R. Stout, and C. D. Wilborn. “Effects of Resistance Training and Protein plus Amino Acid Supplementation on Muscle Anabolism, Mass, and Strength.” Amino Acids 32.4 (2006): 467-77. Web. <http://www.researchgate.net/publication/6805348_Effects_of_resistance_training_and_protein_plus_amino_acid_supplementation_on_muscle_anabolism_mass_and_strength>.
  7. http://www.ncbi.nlm.nih.gov/pubmed/1601794
  8. Roy, B. D., M. A. Tamopolsky, J. D. Macdougall, J. Fowles, and K. E. Yarasheski. “The Effect Of Oral Glucose Supplements On Muscle Protein Synthesis Following Resistance Training 769.” Medicine & Science in Sports & Exercise 28.Supplement (1996): 129. Web. <http://jap.physiology.org/content/82/6/1882>.
  9. Nieman, David C., Sandra L. Nehlsen-Cannarella, Omar R. Fagoaga, Dru A. Henson, Alan Utter, J. Mark Davis, Franklin Williams, and Diane E. Butterworth. “Influence of Mode and Carbohydrate on the Cytokine Response to Heavy Exertion.” Medicine & Science in Sports & Exercise30.5 (1998): 671-78. Web. <http://www.ncbi.nlm.nih.gov/pubmed/9588607>.