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The science of nutrient timing

Die Wissenschaft des Nährstofftimings

James T. Kirk and the crew of the starship Enterprise believed that space was the final frontier - an undiscovered territory with alien worlds, unknown life forms and new civilizations. And so they set out to go where no man had gone before.

Under the leadership of Kirk and his crew, a new generation of nutrition and exercise scientists have embarked on their own voyage of discovery to explore the background of human physiology. Here on Earth, nutrition and exercise researchers have come to the conclusion that the final frontier of muscle building is nutrient timing. And while the science of nutrient timing isn't nearly as exciting as beaming women from alien galaxies aboard your spaceship, if you use it right, this science could help you land some hot women from this galaxy.

What is nutrient timing?

In terms of manipulating body composition and athletic performance, traditional nutritionists have spent much of their time trying to figure out how much and what you should eat to do this. Of course, both of these approaches are of enormous value. Although a myriad of factors influence energy balance (many more factors than a simple assessment of how much you eat and how much you exercise), the laws of thermodynamics are the primary determinant of weight gain and weight loss. Therefore, the question of how much you eat is crucial when it comes to changing your body composition (and indirectly your performance).

But the conventional thermodynamics approach only tells you part of the story. Ultimately, very few people would benefit from focusing solely on weight gain or weight loss. Instead, the focus should be on the composition of the gains or losses. If you are losing equal amounts of fat and muscle in a state of negative energy balance, or gaining equal amounts of fat and muscle in a state of positive energy balance, then you are probably not using the full spectrum of nutrition and training information available to your advantage.

While this may be an oversimplified view of a very complex topic, the thermodynamic approach of measuring calorie intake versus calorie expenditure can in some ways maintain the status quo of body shape. If you have the right genetic predispositions, then the calorie intake vs. calorie expenditure approach may even be all you need to look better naked at any body weight.

But if this isn't the case, then simply counting calories will probably just make you a lighter or heavier version of your former self - and if you're unhappy with your shape, then you won't necessarily like the lighter or heavier version of this).

To get around some of the limitations of the thermodynamic or calorie balance approach, scientists have studied the effects of food choices on changes in body composition. Although these studies are still in their infancy, it is becoming increasingly clear that there is something to the "good" food thing. Despite what naysayers say, once the energy balance is covered, some carbohydrates are better than others. Likewise, some proteins are better than others and some fats are better than others.

Therefore, even if you eat the same amount of calories, choosing foods wisely can upregulate your metabolism, shift your hormonal profile and change the composition of your weight gain or loss - not to mention the health benefits of better diet composition.

As you can see, the science of what you eat has added to the previous big picture, which only considered calories, and expanded our understanding of how to manipulate body composition. By considering the laws of thermodynamics and eating accordingly, we can pave the way for weight loss or weight gain. And by choosing our foods wisely, we could take control of what kind of gains or weight losses we will see. In some ways, the science of what we should eat has given us the power to overcome some of our genetic tendencies (i.e. overall body shape).

While approaches that take into account how much we eat and what we eat already provide us with a ton of great nutritional information, a new field of research looking at nutrient timing has shown that manipulating the temporal dimension can further help us take control of our body composition and athletic performance. For this reason, nutrient timing - or the science of when you should eat - is becoming an important part of nutrition planning.

What's so special about when we eat?

For the average person who doesn't exercise, the principles of nutrient timing aren't particularly important. Sure, glucose tolerance/insulin sensitivity changes throughout the day, but these changes are usually not critical when it comes to determining nutritional needs. For these people, what and how much they eat is the most important thing. However, while nutrient timing may not be critical for the average person, its importance for athletes should not be underestimated - and this applies to all types of athletic disciplines from team sports to endurance sports to training with weights.

In their book "Nutrient Timing" by Dr. John Ivy and Dr. Robert Portman, you will find an excellent commentary on the current state of sports nutrition practice. In this book, the authors highlight the fact that as scientists began to learn more about the nutritional needs of athletes (i.e. higher energy requirements and the benefits of increased protein intake), many athletes have adopted an attitude of "if protein is good, then more protein is better". In other words, this means that when an athlete finds out that something is "good", they will try to get a lot of it. And for many athletes, the reverse is also true, if they find out that something is 'bad', they will try to avoid it at all costs.

Unfortunately, this is nothing more than a combination of the "how much" and the "what" approach to nutrition. Combine this with a very naive good vs. bad approach to nutrition and you have the perfect recipe for a sub-optimal food intake. Ultimately, very few foods are always good or always bad. This is unfortunate for two reasons.

First, much of the current scientific evidence points to the fact that if you exercise regularly, your body is as much pre-programmed to gain or lose fat as it is to gain or lose muscle at certain times of the day. Add the wrong foods at the wrong times and you will sabotage your efforts in the gym. Add the right foods at the right times and you will see a huge boost forward.

Secondly, some foods (e.g. sugar), although not optimal at certain times of the day, can be very beneficial at other times of the day (e.g. post-workout).

Now let's move beyond the overly simplistic approach to nutrition and take a look at the basics of nutrient timing. In their book, authors Dr. Ivy and Dr. Portman point to three critical times of the day during which nutrient timing is of greater importance. They refer to these three times as the energy phase, anaerobic phase and growth phase. I will add to these three phases another phase that I call the "rest of the day phase".

Nutrient timing - the energy phase

The energy phase is so named because this is the phase during training when energy requirements are at their highest. As you probably know, ATP is the form of energy used by skeletal muscle. This ATP is formed from macronutrients in the diet, which means that carbohydrates, proteins and fats indirectly contribute to the energy of muscle contractions.

The high rates of energy demand during exercise are therefore covered by nutrients consumed and/or stored (the ratio depends on the timing of food intake). This breakdown of nutrients - even if it is absolutely necessary - is by definition catabolic. For this reason, the training phase is characterized by a series of anabolic and catabolic effects.

Anabolic effects of acute training

Catabolic effects of acute training

Increased blood flow to the skeletal muscles

Depletion of glycogen stores

Increased release of anabolic hormones

Increased cortisol levels

Dehydration (endurance training or training in extreme heat)

Negative net protein balance

Reduced insulin levels

Increased metabolic rate

Although these phenomena are nothing new and occur during most types of exercise, the idea that targeted nutritional intake can shift the anabolic/catabolic balance during exercise and enhance some of the anabolic effects of exercise while reducing some of the catabolic effects is still something relatively new (1; 4; 10; 11; 17).

Here's an example: a protein-carbohydrate supplement consumed pre-workout or in sips during exercise can increase blood flow to skeletal muscle. Since this drink not only increases blood flow, but also enriches the blood with amino acids and glucose, the protein balance of the trained muscle will shift towards a positive protein balance, while the depletion of glycogen stores is significantly slowed down. In addition to this, these amino acids and these glucose units, regardless of their effects on muscle protein and glycogen status, can lead to a reduction in cortisol concentrations and improve the overall immune response.

When consumed in liquid form throughout the training session, this supplement can also prevent dehydration, which is a potent performance killer in both endurance and strength athletes. That's not too shabby for a little old protein-carbohydrate drink, is it?

The "when", the "what" and the "how much" of the energy phase

When you look at the science of nutrient timing in detail, it becomes clear that one of the key phases for nutritional intake is the period of the energy phase, or the period during exercise. Of course, we should not neglect the "what" and the "how much". These will probably be your next two questions, which is why we will address them here.

As mentioned above, it is important to consume some protein and carbohydrates during the energy phase. In my experience, the easiest way to do this is to consume an easily digestible carbohydrate - protein drink. This drink could consist of a well diluted (a 6 to 10% solution, which means 60 to 80 grams of powder to one liter of water) combination of glucose, maltodextrin and whey protein or hydrolyzed whey protein. Proper dilution is important, especially if you are an endurance athlete or training in a hot environment. If you don't dilute your drink enough, you may not be replenishing your body's water stores at an optimal rate (9, 12).

Now that we know when and what to drink, the next question is how much of it. Unfortunately, this question is not so easy to answer. How much you should eat has a lot to do with how much energy you expended during your training session, how much you consume during the rest of the day, whether your primary goal is to build muscle or lose fat, and a number of other factors. However, to give a simple answer, I would recommend starting with 0.8 grams of carbohydrate and 0.4 grams of protein per kilogram of body weight, diluted with about a liter of water over the duration of your workout (5, 17-20). For a person weighing 100 kilograms, this would be 80 grams of carbohydrates and 40 grams of protein during training.

Nutrient timing - the anabolic phase

The anabolic phase begins immediately after training and lasts for one to two hours. This phase is called "anabolic" because the muscle cells are prepared for muscle growth during this period. Interestingly, even though the cells are being prepared for growth, this phase can remain catabolic in the absence of a good nutritional strategy.

Without adequate nutrient intake, the phase immediately following strength or endurance training is characterized by net muscle catabolism - that's right, muscle tissue continues to be broken down even after training. If you are now asking yourself how this can be, then you are asking the right question. Ultimately, training (and especially training with weights) should make you more muscular, not leaner. And even if you are an endurance athlete, training should not break down your muscles. So how can exercise be so catabolic?

Well, even though the first few hours after exercise induce a net catabolic state (although the rate of protein synthesis increases after exercise, so does the rate of protein breakdown), the body begins to transition to an anabolic state later in the recovery cycle (8, 14). So we typically break down muscle tissue for a while after exercise and then start to rebuild it - and more muscle tissue - later.

However, there is new scientific research that shows that with the right nutritional intervention (protein and carbohydrate supplementation), we can get the repair and rebuilding process to occur during and immediately after exercise (16, 17). Best of all, if we do the nutritional thing right, not only can we activate the repair process faster during and after exercise, but we can also alter the changes in muscle size and/or quality afterwards (16).

The "when", the "what" and the "how much" of the anabolic phase

From now on, when planning your nutrient intake, it's better to consider the energy phase and the anabolic phase as the two key phases of nutrient timing. To maximize your muscle gains and optimize your recovery, you should therefore consume nutrients both during and immediately after training. And again we come to the question of "what" and "how much".

As mentioned above, it is important to consume protein and carbohydrates during the anabolic phase. As with the energy phase, in my experience it is easiest to do this with the help of an easily digestible carbohydrate and protein drink. This drink could consist of a well diluted (a 6 to 10% solution, which means 60 to 80 grams of powder to one liter of water) combination of glucose, maltodextrin and whey protein or hydrolyzed whey protein.

Although the dilution in this case is not as important for rehydration as during the energy phase, as you have already stopped training - and probably sweating - the dilution now serves to prevent digestive problems. I won't go into the details at this point, but simply ask you to take my word for it. You need to dilute.

Now that we know what we should be eating and when we should be eating it, it's time to figure out how much of it we should be eating. Just like during the energy phase, the "how much" has a lot to do with how much energy you expended during your workout, how much you eat during the rest of the day, whether your primary goal is to build muscle or lose fat, etc.

However, just as with the energy phase, a simple recommendation during the anabolic phase is to consume another serving of a drink consisting of 0.8 grams of carbohydrate and 0.4 grams of protein per kilogram of body weight diluted with approximately one liter of water (5, 17-20).

If you add up the basic recommendations of the energy phase and the anabolic phase, you will find that I have recommended a total consumption of 1.6 grams of carbohydrates and 0.8 grams of protein. For a 100 kilo person, this would be a total of 160 grams of carbohydrates and 80 grams of protein during and immediately after training. Based on what you would normally consider "a lot" of carbs, this may or may not look like a lot of carbs to you.

Regardless, it's important to understand that during and after exercise, insulin sensitivity and glucose tolerance are very good (2, 3, 13, 15, 21). Even if you believe you have poor carbohydrate tolerance based on your experience (which too many people do for no real reason), your carbohydrate tolerance will be much better during and after exercise.

And when you consider that most of the carbohydrates you consume during and immediately after exercise are either burned for energy or used to replenish glycogen stores in muscles and liver (even at elevated insulin concentrations) and that the post-workout phase is characterized by a dramatic increase in the rate of fat metabolism (6,7), it should be clear that even a drink with plenty of carbohydrates and protein will not directly lead to an increase in body fat.

However, you should ensure that you compensate for this increased carbohydrate intake during and after exercise by reducing your carbohydrate intake during other times of the day when glycogen resynthesis is not as efficient and an increase in insulin levels is not as beneficial.

For this consideration, it should be clear that using the principles of nutrient timing, you can fuel your body with carbohydrates during and after exercise while reducing your carbohydrate intake during the rest of the day. By using this strategy, carbohydrates are delivered at the exact time when they can best be converted into muscle glycogen and best stimulate muscle growth and/or repair.

If your goal is to build muscle, you will build more muscle per gram of carbohydrate consumed. If, on the other hand, your goal is to lose fat, then you will store more muscle glycogen and achieve a pronounced muscle-protective effect even if you consume fewer carbohydrates during the day. And if maximum athletic performance is your goal, then your recovery will improve dramatically.

Before we go any further, it's important to understand that the 960 kcal I've recommended for a 100 kilo person is better utilized during and after exercise than at other times of the day and this is the crux of nutrient timing. Nutrients consumed during the energy phase and the anabolic phase can contribute to muscle building, muscle repair and recovery to a greater extent than the same nutrients consumed at other times of the day.

Now that we have covered what you should eat during the energy phase and the anabolic phase, in the second part of this article I will give you some recommendations on what you should consume during the remaining two phases of the nutrient timing cycle.


By John Berardi, PhD

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