Nutrition

This guide will give you an insight into the ketogenic, low-carbohydrate diet and its 3 variations and provide you with some sample recipes for a ketogenic diet.

This guide will cover the following points:

• What ketosis is and how it affects the burning of fat
• The difference between the three standard types of ketogenic diets
• The standard ketogenic diet
• The cyclical ketogenic diet
• The targeted ketogenic diet
• How to put together and fine-tune a ketogenic diet
• What foods you should eat on a ketogenic diet and how much saturated fat is appropriate

An introduction to the ketogenic diet

A ketogenic diet (also known as a "keto" diet) is nothing new, but is a form of nutrition that has enjoyed a strong following in the bodybuilding subculture for decades. In a nutshell, a ketogenic diet is simply a diet that is high in fat and protein and very low in carbohydrates (usually carbohydrates make up less than 10% of the macronutrient intake). Under this condition alone, the body is forced to use fat as an energy source because carbohydrate stores will quickly be depleted.

A ketogenic diet can be effective for many individuals and can also be easily tailored to suit personal goals - whether those goals are to build muscle, lose body fat, develop strength or whatever. Although ketogenic diets are often only used for fitness and health purposes, they are also used in the medical field to treat epilepsy (1).

You might be wondering what makes a ketogenic diet different from any other low-carb diet. The truth is that apart from the fact that some people believe that a ketogenic diet is only effective when the body enters a state known as ketosis, where the body produces ketones or keto bodies as a source of energy, there isn't that much difference. Ketosis - hence the name ketogenic diet - also requires more extreme carbohydrate restriction. However, this assumption is somewhat short-sighted, as we will see later.

In this guide, we'll take a deeper look at the physiology behind the ketogenic diet, the different types and variations of ketogenic diets and how you can create your own ketogenic diet. To make the latter easier for you, we will present a few sample ketogenic recipes and, last but not least, answer some frequently asked questions.

What exactly is ketosis?

The ketogenic diet takes its name from the fact that a severe restriction of carbohydrate intake can induce a state in the body known as ketosis, in which the levels of so-called keto bodies, also known as ketones, are significantly increased.

Ketone bodies are organic, water-soluble biomolecules that are synthesized in the liver from fatty acids when food intake - more specifically, carbohydrate intake - is limited. These biomolecules can be used as an energy source in different types of tissue in the body.

Ketobodies are continuously produced in low concentrations in the body of healthy people, but the concentrations are normally so low that they cannot be detected by urine testing. When the concentrations of ketone bodies in the bloodstream increase (also known as ketonemia), they are also excreted more in the urine (a process known as ketonuria). Ketonemia and ketonuria together make up the state of ketosis.

Ketogenic diets are therefore methods of inducing nutritional ketosis (not to be confused with the harmful pathological ketosis that can occur in diabetics), which ultimately causes the body to rely on fatty acids and keto bodies as its primary energy sources.

The three main types of ketogenic diets

There are three primary variations of ketogenic diets that we will cover in this article:

• The standard ketogenic diet (SKD for short)
• The cyclical ketogenic diet (CKD for short)
• The targeted ketogenic diet (TKD for short)

The type of ketogenic diet you end up using will depend on both your goals and your trial and error experience (more on the specifics below).

The standard ketogenic diet

This is the simplest and most basic variation of a ketogenic diet. Unlike the cyclical and targeted ketogenic diets, the standard ketogenic diet does not have carbohydrate loading phases. Instead, it is a form of nutrition with a static ketogenic food intake (moderate to high protein intake, high fat intake and low carbohydrate intake).

The cyclical ketogenic diet

This variation of the ketogenic diet involves recurring carbohydrate refeeds to help you replenish your muscle glycogen stores for a short period of time after they have been completely depleted. The time window between carbohydrate loading phases can vary depending on your preferences, training intensity and goals.

The targeted ketogenic diet

This final version of the ketogenic diet uses intermittent short periods of carbohydrate intake specifically around the training window. The goal here is to provide you with enough glucose to allow you to maintain your athletic performance without inhibiting ketosis for an extended period of time.

Which type should I use?

The type of ketogenic diet you end up using will be based on several factors. It is generally recommended that you start with a standard ketogenic diet for a few weeks and see how your performance and energy levels feel. From this starting point, you should have a better idea of what form of ketogenic diet you should use in the longer term.

You may also be wondering which type is best for fat loss and which type is best for building muscle. Well, assuming that your calorie intake is where it should be for the goal in question, the type of ketogenic diet you use to achieve your goal won't make too much of a difference to your progress.

Some people may argue that the cyclical and targeted ketogenic diets are better suited to individuals looking to build muscle, as carbohydrates have a protein-sparing effect and are insulinogenic, whereas the standard ketogenic diet is better suited to fat loss, as insulin secretion will remain relatively low. However, these short-term fluctuations in insulin secretion will not play too big a role compared to long-term calorie intake.

Below is a summary of what you should consider when thinking about which version of the ketogenic diet to use:

Standard ketogenic diet

The standard ketogenic diet is best suited to people who are generally sedentary and whose exercise performance is not affected by a sharp reduction in carbohydrate intake. This form of ketogenic diet is also a good option for those who do not exercise very intensively and/or are very insulin resistant.

Targeted ketogenic diet

If you are someone who trains very intensively several times a week and whose training performance suffers from a chronically low-carb diet, it is wiser to use short carbohydrate bursts before and possibly after training. This is also a good option for advanced exercisers who can benefit from short-term carbohydrate intake but do not do well with large carbohydrate meals.

Cyclical ketogenic diet

This form of ketogenic diet is generally considered the most advanced form of ketogenic diet, as it requires some trial and error on the part of the user when it comes to optimizing the time between carbohydrate refeeds and the amount of carbohydrates consumed during these refeeds.

If you are an advanced exerciser who trains intensively throughout the week and feel that your performance is suffering on a standard ketogenic diet and a targeted ketogenic diet, then you should consider a cyclical ketogenic diet and see if it brings your performance back on track.

How to create your own ketogenic diet

Below you will find some necessary steps to calculate your individual energy requirements and your individual macronutrient needs. This will give you a basis for your nutritional intake during a standard ketogenic diet. Users on a targeted or cyclical ketogenic diet can still use their calculations for a standard ketogenic diet with a few adjustments, which I will discuss below.

The general rule of thumb for people who want to lose fat is to aim for a calorie deficit of roughly 500 kcal per day, while those who want to build muscle should aim for a calorie surplus of 500 kcal per day. However, this is a very rough generalization that can vary from person to person depending on their physiological tendencies and other factors. In addition, if you have opted for the cyclical ketogenic diet, it is likely that you will have changed your calorie intake over the course of the week.

Here is an example of how you would calculate the macronutrient intake for a person with 68 kilos of lean body mass on a 2000 kcal fat loss diet:

• Determine your rough calorie requirements using one of the many calorie calculators you can find on the internet.
• Set your protein intake to about 2.2 grams per kilogram of body weight per day: about 150 grams of protein
• Set your carbohydrate intake at 0.2 to 0.5 grams per kilogram of body weight: 15 to 30 grams (we will use 30 grams in the calculations below)
• Since carbohydrates and protein each provide 4 kcal per gram, this equals (150 + 30) x 4 = 720 kcal in the form of protein and carbohydrates.

The remaining calories to reach 2000 kcal per day are the daily fat intake:

2000 - 720 = 1280 kcal / 9 kcal per gram of fat =~-142g of fat per day.

The macronutrient breakdown would therefore be as follows:

• 150 grams of protein per day
• 30 grams of carbohydrates per day
• 142 grams of fat per day

Example with 3 meals per day

• Meal 1-50g protein/10g carbohydrates/48g fat
• Meal 2-50g protein/10g carbohydrates/47g fat
• Meal 3-50g protein/10g carbohydrates/47g fat

Example with 5 meals per day

• Meal 1-30g protein/10g carbohydrates/30g fat
• Meal 2-30g protein/5g carbohydrates/30g fat
• Meal 3-30g protein/5g carbohydrates/30g fat
• Meal 4-30g protein/5g carbohydrates/25g fat
• Meal 5-30g protein/5g carbohydrates/27g fat

Food choices on a ketogenic diet

There are no strict rules about which foods are allowed and which are a no-go on a ketogenic diet. Some people will insist that no starches or sugars should be eaten as these will prevent ketosis from occurring, but with very small amounts of these foods this is very unlikely - which is especially true for heavier people.

During a standard ketogenic diet and the ketogenic phases of the targeted and cyclical ketogenic diets, the following foods are good options due to their inherently low carbohydrate intake and high fat intake:

• Animal proteins (especially red meat)
• Eggs (whole eggs and egg whites)
• Full-fat dairy products such as cheese, cream, butter, etc.
• Oils such as rapeseed oil, peanut oil, linseed oil, macadamia oil, olive oil and coconut oil
• Nuts and variations of nut butters
• High-fiber vegetables and especially green vegetables such as lettuce, broccoli, celery, etc.

During the carbohydrate loading phase of the various ketogenic diets, you can temporarily consume starchy foods and sugars - preferably in the form of fruit.

Changes for a cyclical ketogenic diet

At this point, we will take a look at how you can integrate carbohydrates into a ketogenic diet in a cyclical way.

In a cyclical ketogenic diet, it is wise to start with a once-weekly carbohydrate refeed and adjust the intervals between refeeds as needed. This method will require a lot of personal experimentation as you will need to assess how many carbohydrates you should consume based on how you feel on the days following the carbohydrate intake.

The most important thing to consider when starting a carbohydrate refeed is to limit your fat intake. In other words, you should not continue to consume large amounts of fat during a carbohydrate refeed. Protein intake, on the other hand, should remain the same (or even increase given the amount of calories).

Using the above example person with 68 kilos of lean body mass, here are some basic recommendations on what macronutrient intake might look like on a weekly carbohydrate refeed of a cyclical ketogenic diet based on insulin sensitivity/carbohydrate tolerance:

• Set protein intake at about 2.2 grams per kilogram of lean body mass: about 150g of protein per day
• Low insulin sensitivity: set the carbohydrate intake to 2 to 3.5 grams of carbohydrates per kilogram of fat-free body mass
• Moderate insulin sensitivity: set carbohydrate intake at 4.5 to 5.5 grams of carbohydrates per kilogram of lean body mass
• High insulin sensitivity: set the carbohydrate intake to 6.5 to 7 grams of carbohydrates per kilogram of fat-free body mass
• As before, calculate the total amount of calories and divide the remainder by 9 to find out how much fat you should eat on your carbohydrate loading days.

Note: If you are on a fat loss diet and have a moderate to high insulin sensitivity, you can increase your calorie intake on the carbohydrate refeed days to the maintenance calorie amount (or maybe even slightly above).

Example of a cyclical ketogenic diet for a person with moderate insulin sensitivity, 68 kilos of lean body mass during a fat loss diet with a calorie intake of 2000 kcal per day

• Monday to Friday - follow the nutrient breakdown described above for a standard ketogenic diet
• Sunday (carbohydrate refeed, 2500 kcal)-150g protein/300g carbohydrate/~78g fat
• Example of a cyclical ketogenic diet for a person with high insulin sensitivity, 68 kilos of lean body mass during a mass building phase with a calorie intake of 3000 kcal per day
• Monday to Friday - follow the nutrient breakdown described above for a standard ketogenic diet
• Sunday (carbohydrate refeed,)-150g protein/450g carbohydrate/~67g fat

Changes for a targeted ketogenic diet

Let's take a look at how carbohydrates can be used in a targeted way as part of a ketogenic diet (e.g. pre- and post-workout).

Similar to a cyclical ketogenic diet, a targeted ketogenic diet will take some time to figure out how your body responds to a certain amount of carbohydrate and what is the best way for you to time your carbohydrate intake.

Remember that the goal of a targeted ketogenic diet is to consume a sufficient amount of carbohydrates to promote performance benefits without overdoing it on the carbs. A cyclical ketogenic diet is designed to replenish glycogen stores, whereas a targeted ketogenic diet is used more for a short-term energy/performance boost.

Assuming that a person trains intensively 5 days per week, this person would consume carbohydrates with pre- and/or post-workout meals on these days. On the other two days, this person would eat the same macronutrient breakdown as during a standard ketogenic diet.

The nutrient breakdown during a targeted ketogenic diet is the same as a standard ketogenic diet, except that on training days carbohydrates are used around training. Let's look at a possible nutrient breakdown during a targeted ketogenic diet using our example person with 68 kilos of lean body mass during a 2000 kcal fat loss diet depending on the insulin sensitivity/carbohydrate tolerance as a parameter to determine the carbohydrate intake around training:

• Set protein intake at around 2.2 grams per kilogram of fat-free body mass: approx. 150g protein per day
• Low insulin sensitivity: add 0.6 grams of carbohydrates per kilogram of lean body mass to the diet during the training window
• Moderate insulin sensitivity: add 0.8 grams of carbohydrates per kilogram of lean body mass to your diet during the training window
• High insulin sensitivity: add 1.1 grams of carbohydrates per kilogram of lean body mass to your diet during the training window

Now you simply factor in the additional carbohydrates alongside your protein intake and fill the rest of your calories with fat, as we did previously with the cyclical ketogenic diet.

Note: The additional carbohydrate intake relates to the time window around your training. This means you can divide these carbohydrates up as you wish between before, during and after your training, as long as they are consumed within this time window. It is generally recommended to simply split the carbohydrate intake in half and consume one half before and the other half after your workout

Example of a targeted ketogenic diet for a person with low insulin sensitivity, 68 kilos of lean body mass during a fat loss diet with a calorie intake of 2000 kcal per day

• Training days - follow the above nutrient breakdown for a standard ketogenic diet and add 38 grams of carbohydrates around your workout.
• Non-training days - follow the nutrient breakdown for a standard ketogenic diet as described above.
• Example of a targeted ketogenic diet for a person with high insulin sensitivity, 68 kilos of lean body mass during a mass gain phase with a calorie intake of 3000 kcal per day:
• Training days - follow the above nutrient breakdown for a standard ketogenic diet and add 75 grams of carbohydrates around your workout.
• Non-training days - follow the nutrient breakdown described above for a standard ketogenic diet

Example nutrition plan during a targeted ketogenic diet with 5 meals (training day)

Note: The values are based on a person with 68 kilos of lean body mass and a high insulin sensitivity during a 3000 kcal mass-building phase.

• Meal 1 (pre-workout)-30g protein/40g carbohydrates/20g fat
• Meal 2 (after training)-30g protein/35g carbohydrates/20g fat
• Meal 3-30g protein/10g carbohydrates/60g fat
• Meal 4-30g protein/10g carbohydrates/60g fat
• Meal 5-30g protein/10g carbohydrates/60g fat

In the second part of this article, we'll look at some other aspects of ketogenic diets and give you a small collection of sample ketogenic meal recipes before answering some frequently asked questions about a ketogenic diet.

Source: https://www.muscleandstrength.com/expert-guides/keto-diet

After describing the basics of protein metabolism and the effects of insulin and IGF-1 on it in the first part of this article, in this second part we will take a closer look at the influence of growth hormones, androgens, oestrogens, thyroid hormones and stress hormones on protein metabolism.

Growth hormones

Growth hormones are peptide hormones that are produced in the pituitary gland and stimulate cellular growth and cellular reproduction. When the body is well nourished, growth hormones stimulate the production of insulin in the pancreas and IGF-1 in the liver, which subsequently stimulates the growth of lean body tissue and adipose tissue, as well as the storage of glucose. During fasting or other catabolic states, growth hormones stimulate the release and oxidation of fatty acids for the purpose of providing energy to the body, thus protecting lean body mass and glycogen stores (11).

Growth hormones appear to be the most misunderstood hormones in the human body. Some so-called "fitness gurus" claim that these hormones are neither anabolic nor do they make sense from a health perspective (which are quite arrogant claims considering the scientific research that shows the opposite). Growth hormones do indeed have a number of anabolic effects in the human body, but these are mechanistically different from those of insulin. Growth hormone could be considered the primary anabolic hormone during stress and fasting, whereas insulin is the primary anabolic hormone during the post-fasting window.

Scientific research has shown that growth hormones strongly inhibit amino acid oxidation (remember that amino acids can be burned for energy). Thus, growth hormones protect the amino acid pool from depletion, resulting in a higher availability of amino acids for incorporation into proteins (11).

Growth hormones appear to alter whole body protein synthesis in the short term and any increases in muscle protein synthesis due to growth hormone release are also likely to result in subsequent local IGF-1 release. Both growth hormone and testosterone (which we will discuss later) increase local IGF-1 levels, which can promote anabolic effects in skeletal muscle tissue.

Surprisingly, scientific studies have shown that exogenous administration of IGF-1 suppresses local IGF-1 production in muscle tissue, resulting in no increase in muscle protein synthesis (7, 12, 13). Thus, the use of IGF-1 as a performance-enhancing substance appears to be useless when it comes to increasing muscle growth.

It has been shown that growth hormones not only promote protein synthesis but also inhibit protein degradation and it is likely that this effect is due to local production of IGF-1 in muscle tissue (14). The reason for attributing the anabolic effects to growth hormones is quite simple, as growth hormones cause an increase in IGF-1 production.

A final point to consider regarding the anabolic effects of growth hormones is that growth hormones accelerate the transport of certain essential amino acids across the cell membrane, which is particularly true for amino acids transported via system L - the primary transport system responsible for sodium-independent transport of neutral amino acids such as leucine, isoleucine and valine (15).

Growth hormone summary:

Growth hormones are highly complex hormones that are under intense investigation as many of its in vivo actions are not yet fully understood.

In summary, growth hormones are potent hormones that promote body-wide protein synthesis and reduce body-wide protein degradation - and it is likely that these effects also occur in skeletal muscle tissue once growth hormone-induced local IGF-1 production begins (it is hoped that further studies will be conducted on this topic in the coming years).

Growth hormones also strongly inhibit amino acid oxidation and increase the transmembrane transport of amino acids such as the branched-chain amino acids leucine, isoleucine and valine. In addition, it should be noted that growth hormones strongly influence fat loss, as they promote the use of fatty acids for the purpose of supplying the body with energy.

As mentioned in the IGF-1 section, numerous factors are involved when it comes to when and how much growth hormone is released. Since growth hormone is secreted in a pulsatile manner (with approximately 50% of the total amount of growth hormone secreted daily being secreted during sleep), it makes sense to consider the following factors that stimulate and inhibit growth hormone production:

Factors that stimulate growth hormone secretion (16-22):

• Sex hormones (androgens and oestrogens)
• Peptide hormones such as ghrelin and growth hormone-releasing hormone (GHRH)
• L-DOPA, the precursor of the neurotransmitter dopamine
• Nicotinic acid (vitamin B3)
• Nicotine receptor agonists
• Somatostatin inhibitors
• Fasting
• Deep sleep
• Intensive training

Factors that inhibit growth hormone secretion (18, 23-26):

• Somatostatin
• Hyperglycemia(carbohydrates in the bloodstream)
• IGF-1 and growth hormone (due to negative feedback inhibition of the pituitary gland)
• Xenobiotics
• Glucocorticoids
• Certain sex hormone metabolites such as dihydrotestosterone (DHT)

Androgens

Many readers will probably be familiar with the term anabolic androgenic steroid, which is often used in the media and fitness subculture. This already tells you that androgens are indeed anabolic hormones - and they influence the development and maintenance of the male sexual organs, as well as the characteristics of the male sex.

Several different androgens are produced in the human adrenal glands, but the primary androgen we will focus on here is the male sex hormone also known as testosterone (produced primarily in the testes in men and ovaries in women), as it is the body's most potent natural anabolic steroid.

There is a significant amount of research showing that this hormone plays a leading role in the growth and maintenance of skeletal muscle. In studies where men suffering from testicular hypofunction were given a replacement amount of this androgen, it was observed that lean body mass, skeletal muscle strength and muscle protein synthesis increased dramatically (27, 28, 29). These effects have also been observed in trained athletes and normal, healthy men following the administration of pharmacological doses of various androgens (30, 31).

It appears that androgens, like growth hormones, exert some of their anabolic effects by reducing amino acid oxidation (particularly leucine) and increasing the uptake of amino acids into body proteins, including muscle proteins (32).

In addition, there appears to be a synergistic (but independent) anabolic effect between testosterone and growth hormones, which mutually reinforce their benefits on skeletal muscle protein synthesis (33).

Androgen Summary:

There are many reasons that the primary male sex hormone and other androgens are being studied so intensively and it is quite clear that these compounds have a variety of anabolic effects in the human body. Primary male androgen is a potent inhibitor of amino acid oxidation and increases body-wide protein synthesis including skeletal muscle protein synthesis (and also appears to have anti-proteolytic effects (34).

As with growth hormone and IGF-1, many factors play a role in regulating the production of this androgen. Below is an abbreviated list of these variables.

Factors that positively influence androgen production/levels (35-40):

• Adequate amounts of sleep
• Fat loss (to a certain extent, as fat cells secrete the aromatase enzyme that converts androgens to estrogen)
• Intense exercise (especially resistance training)
• D-aspartic acid supplementation
• Vitamin D supplementation
• Abstinence (for about a week at a time)

Factors that negatively affect androgen production (26, 38, 39, 41-43):

• Obesity/overweight
• A lack of sleep
• Diabetes (especially insulin-resistant/type 2 diabetes)
• A sedentary lifestyle / inactivity
• Very low-fat diets
• Prolonged aerobic activity
• Excessive alcohol consumption
• Xenobiotics

Estrogenic hormones

Oestrogens are the basic female sex hormones and are responsible for the growth and maturation of female reproductive tissue - but they are also present in the male body (albeit in lower concentrations). Three primary oestrogens are produced in the human body: oestradiol, oestrone and oestriol. Oestradiol is about ten times more potent than oestrone on a molecular basis and 80 times more potent than oestriol in terms of oestrogen effect.

In women, most oestrogens are produced in the ovaries via aromatization of androstenedione, while in men it is produced in small amounts in the testes and to a greater extent via aromatization of testosterone in the fat cells.

Unlike all the other hormones we have looked at so far, estrogen appears to have both anabolic and catabolic properties when it comes to protein metabolism (mainly by influencing other hormones in the body).

Studies have shown that estrogens can increase growth hormone levels and local IGF-1 levels, both of which have positive effects on protein anabolism and anticatabolism. (44, 45, 46). In addition, estrogens promote water retention, which is beneficial for cell volumization and thus anabolism.

When excessive amounts of estrogen are present, it can have an indirect catabolic effect via blockade of androgen receptors and downregulation of gonadotropin-releasing hormone production in the hypothalamus, which ultimately decreases androgen production in the body.

Estrogen Summary:

As with many other things in the health and fitness world, there is a balance to be found with estrogen levels. Estrogens have many important effects in the human body and even some anabolic/anti-catabolic effects on protein metabolism.

However, you should be careful, as excessive estrogen levels (especially in men) are likely to decrease androgen production and availability, thereby interfering with the positive effects of androgens on protein metabolism.

Some general tips for balancing your estrogen production include (47 - 50):

• Eating a balanced diet that includes adequate amounts of vitamins, minerals and fiber
• Limiting the consumption of soy and phytoestrogens from plant sources
• Limiting alcohol consumption, as this impairs the liver's ability to metabolize estrogens
• A regular exercise program
• Maintaining a healthy body weight, which includes avoiding obesity as well as being severely underweight

Thyroid hormones

Thyroid hormones are a master regulator of metabolic rate and affect nearly every cell in the human body. The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), with T4 being the prohormone of T3. On a molar basis, T3 is about 20 times more potent than T4 and is therefore considered the "true" thyroid hormone (most of the circulating T3 consists of deiodinated T4).

Scientific research seems to suggest that thyroid hormones can increase both body-wide protein synthesis and body-wide protein breakdown, with the latter effects being more pronounced, resulting in a net catabolic effect on total body protein metabolism (51, 52).

In general, thyroid hormones play a fundamental role in the regulation of protein metabolism in normal physiological ranges and it is inappropriate to conclude from data obtained in the context of synthetically induced hyperthyroidism that normal thyroid function is inherently catabolic.

Nor does there appear to be any benefit in terms of skeletal muscle anabolism or whole body protein anabolism from an increase in thyroid hormone production or use of exogenous thyroid hormones - and if there is an effect, it is likely to be catabolic in nature.

Thyroid Hormones Summary:

As the main aim of this article is to examine the effects of these hormones/factors on protein metabolism, the above section does not cover the role that thyroid hormones play in carbohydrate and fat metabolism. It is sufficient for you to know that the catabolic nature of thyroid hormones means that they would have a beneficial effect on fat loss due to the upregulation of metabolic rate (this is also the reason why people who suffer from hyperthyroidism are usually underweight and/or have a hard time gaining weight).

However, if your goal is anabolism (especially of skeletal muscle tissue), then manipulating your thyroid hormone levels doesn't seem wise. This means that the best way to support optimal protein metabolism is to simply maintain normal thyroid function within the normal physiological range.

"Stress hormones" glucocorticoids (primarily cortisol), glucagon and epinephrine

The term "stress hormone" is often used in the scientific literature when referring to glucocorticoids (primarily cortisol), glucagon and catecholamines (more specifically epinephrine/adrenaline). This is primarily due to the fact that the release of these hormones is stimulated in response to stress (in this context it is important to understand that stress does not always have to be a bad thing).

Glucocorticoids are a class of steroid hormones produced in the adrenal glands that regulate metabolism, development, immune function and alertness. The primary glucocorticoid in humans is the stress hormone cortisol. Cortisol is an essential hormone that is necessary for the maintenance of life, but like many other hormones, too high (or too low) levels can have devastating consequences for the body.

Cortisol is often involved in the process of muscle atrophy/degradation as it acts primarily as a catabolic hormone in terms of its metabolic functions. During periods of malnutrition/fasting, cortisol helps to maintain normal blood glucose concentrations by initiating gluconeogenesis. This is often done at the expense of protein degradation in order to use amino acids as substrates for the process of gluconeogenesis.

Glucagon is a peptide hormone produced by the pancreas that basically has the opposite effect of insulin (i.e. it stimulates the release of glucose from the liver into the bloodstream when blood glucose levels fall). Similar to cortisol, glucagon also influences gluconeogenesis and glycogenolysis.

The final hormone in this triad is epinephrine/adrenaline (which is sometimes referred to as the "flight-or-fight" hormone). This hormone is produced by the central nervous system and the adrenal glands and acts in pretty much all tissue types in the body by docking to the adrenoceptors. Just like cortisol and glucagon, epinephrine also stimulates glycogenolysis in the liver and muscles.

Protein synthesis rates in skeletal muscle tissue appear to decrease dramatically in response to stress hormones (53, 54, 55). Prolonged exposure to stress hormones impairs protein synthesis, leading to atrophy of muscle tissue (56).

It is also important to note that epinephrine and cortisol can inhibit insulin secretion - remember that insulin is an anabolic hormone. Some research also suggests that cortisol reduces local synthesis of IGF-1, which would be counterproductive to the goal of protein anabolism (57).

Stress hormones Summary:

The bottom line here is not that stress hormones are some sort of diabolical hormones to be avoided or suppressed at all costs, as this is frankly not what is desirable (in fact, stress hormones are vital in many ways).

The data seems to show that an intake of these hormones promotes protein breakdown and stimulates oxidation of amino acids in most tissue types in the body. They can also impair protein synthesis at chronically elevated levels and reduce insulin secretion and the local release of IGF-1. Ultimately, the accumulation of these actions results in a net catabolic effect.

However, you should not misconstrue this message to mean that acute surges of these hormones (as can be observed during periods of acute stress) are counterproductive to muscle growth, as this would ignore the bigger picture - to reiterate, stress hormones are a necessary part of human physiology. Unless you suffer from abnormally high levels of cortisol, glucagon or epinephrine in the blood over a prolonged period of time (as is the case with Cushing's syndrome, chronic stress, etc.) there is probably no reason to worry about lowering or inhibiting these hormones, as this would be neither beneficial nor healthy.

Let's put it all together

Even though this article is packed with scientific jargon, I hope it has given the reader an understandable overview of some of the primary factors that influence protein metabolism. This is a complex topic and protein metabolism is a growing field of research, which is what makes it so interesting to look at and discuss in more detail.

It is not the intention of this article to advocate the use of any of the compounds or hormones described in the reviews. The options described in this article for modulating the levels of some of these hormones only concern the body's own production and not the administration of exogenous hormones.

Last but not least, remember that many physiological processes are not black or white or on/off switches. It is always crucial that we consider the circumstances and context of the situation. It is neither purposeful nor wise to ignore individual variables that come into play when giving someone advice on nutrition and training.

For this reason, this article is only intended to serve as a broad overview of the factors that influence and/or regulate protein metabolism and to provide you, the reader, with the necessary information to help you make optimal nutritional and lifestyle choices to achieve your individual goals.

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Source: https://www.muscleandstrength.com/expert-guides/protein-anabolism-catabolism

This guide includes the following:

• The exact meaning of the term metabolism.
• Which are the primary factors that influence catabolism and anabolism.
• What influence insulin has on protein synthesis.
• What role nutrition plays in growth hormone, insulin and IFG-1 production.
• How testosterone plays a significant role in the growth and maintenance of skeletal muscle tissue.
• The role of the three primary estrogens produced in the human steroidogenesis pathway: Estradiol, estrone and estriol.
• Why thyroid hormones are a key regulator of human metabolism.
• Why stress hormones are not something to be avoided/suppressed at all costs.

The two terms thrown around the most in the bodybuilding subculture are "anabolic" and "catabolic". However, I could bet that most people don't know much about these terms beyond the fact that the first term has something to do with building and the second term has something to do with breaking down.

Considering that the primary focus of many competitive and recreational athletes is to improve their body composition, muscle hypertrophy and fat loss are often their primary interests. Therefore, it seems wise to cover the basics of what anabolism and catabolism mean in this context. Furthermore, it is important to understand what these classes of reactions mean in the grand scheme of things for a living organism.

This series of articles is designed to cover the primary factors of the human endocrine system and their role in protein anabolism and catabolism.

What is metabolism?

Metabolism is one of those terms that pretty much everyone knows (and uses) but few really understand, which is why this section will serve to give you a basic idea of what metabolism is exactly.

All living organisms are made up of the simplest living unit - the cell. Yes, this means that even simple microorganisms are "alive", although of course humans are made up of an enormous amount of cells (hundreds of trillions of cells) and are very brain-heavy, whereas many microbes are made up of only a single cell (and have no brain). But I digress...

But back to the topic at hand - chemical reactions are continuously occurring within these cells, consuming or releasing energy as part of the process. These reactions are divided into two classes, which we have already discussed in the introduction: anabolic and catabolic reactions. The former use energy to build cellular components and molecules, while the latter release energy as they break down complex structures.

Therefore, when we speak of metabolism, we are referring to the summation of all these physiological reactions within the cell that are necessary to sustain life. A multitude of variables such as hormonal signals, physical activity, nutrient availability and energy status influence how these reactions occur and when they take place. For now, it is only important that you know that metabolism is a highly intricate system of reactions in cells that sustains life and that there is an inherent energy uptake and an inherent energy release through these processes (hence the need for nutrients).

Improving body composition

The goal of most individuals in the gym is to improve their body composition (i.e. reduce their body fat percentage and/or increase their muscle mass). The complicated part is that improving body composition is a process of give and take. In the bodybuilding and fitness subculture, many people are obsessed with the idea of losing fat and building muscle at the same time.

However, these events are mutually exclusive, at least in theory, as one of the two scenarios requires an energy deficit and the other requires an energy surplus. When I come across one of these trainers or magical programs that guarantee they will help build muscle and lose fat at the same time, I know it's a pretty arrogant claim unless these people or programs manage to overcome the laws of thermodynamics.

One way to think of improving body composition is to swing back and forth between building muscle and losing fat - if you want to increase one of the two, the other must be reduced.

This is why the traditional approach of many gym-goers who want to improve their body composition is to alternate between phases of muscle building and fat loss. This is usually referred to as bulking and dieting. The other option is to be constantly in a maintenance phase (during which you neither gain nor lose muscle or fat). So let's take a look at the role of protein anabolism and catabolism when it comes to improving body composition.

Protein and the development of skeletal muscle tissue

Skeletal muscle tissue serves as the largest reservoir of amino acids in the human body. Many bodybuilders and health enthusiasts love to debate the topic of protein intake - mainly because proteins provide the "building blocks" / amino acids responsible for the synthesis of muscle tissue.

Many people misinterpret the message being sent when someone refers to protein synthesis. Proteins are basically macromolecules that play a variety of roles in humans. They are not only related to muscle tissue, but are ubiquitous in many body systems:

• Whole body protein turnover - this is a measure of the synthesis and breakdown of all proteins in all organs and body tissues
• Skeletal muscle protein turnover - this is a measure of synthesis and breakdown in the skeletal muscle area.

If we're looking to improve body composition, then intuitively it should make sense that we're trying to build skeletal muscle tissue specifically, as we're not looking to hypertrophy, say, kidney tissue (well, at least not chronically). Now of course this doesn't mean that whole body protein anabolism is a bad thing (which is ultimately a crucial part of human existence), just that exorbitant whole body protein anabolism over a prolonged period of time can lead to organ enlargement and ultimately health problems.

Synthesis, breakdown, turnover, anabolism, catabolism, hypertrophy... "I'm lost, help!"

Before we continue, for those who find all the technical terms a little confusing, here is a brief overview of some of the terms used in this article:

• Muscle protein synthesis-Thisterm refers exclusively to the synthesis of protein in skeletal muscle tissue
• Muscleprotein breakdown-Thisterm refers exclusively to the breakdown of skeletal muscle tissue
• Protein turnover-Theprotein turnover is a measure of the ratio of protein synthesis to protein breakdown
• Muscle protein anabolism-Thisterm refers to a condition in skeletal muscle tissue in which muscle protein synthesis exceeds muscle protein breakdown, resulting in a build-up of muscle tissue
• Muscleprotein catabolism-Thisterm refers to a condition in skeletal muscle tissue in which muscle protein breakdown exceeds muscle protein synthesis, resulting in muscle tissue buildup
• Hypertrophy-Thisis another term for the growth of tissue (generally with regard to muscle)
• Atrophy-Thisterm refers to a breakdown of tissue and is the opposite of hypertrophy

Primary hormones and factors to consider with regard to skeletal muscle protein anabolism and catabolism

Okay, now we have arrived at the actual topic of the article and are going to look at the factors that play a major role in protein anabolism and protein catabolism and thus ultimately have an impact on body composition. As previously mentioned, anabolic reactions serve to build cellular components and molecules, while catabolic reactions do the exact opposite. Also, remember that anabolic reactions require an energy input and catabolic reactions release energy. We'll take a more detailed look at what role protein anabolic and protein catabolic reactions play in terms of building skeletal muscle tissue - one of the most important components in improving body composition.

Here is a brief preview of the topics we will be looking at in this context:

• Amino acid pool, transport and oxidation
• Insulin
• Insulin-like Growth Factor-1 (IGF-1) and IGF-Binding Protein-3 (IGFBP-3)
• Growth hormones
• Androgenic hormones
• Oestrogenic hormones
• Thyroid hormones
• "Stress hormones" - glucocorticoids, glucagon and catecholamines

Keep in mind that many of the hormones and factors described in this article interact to some degree, making it nearly impossible to isolate these components.

Amino acid pool, transport and oxidation

As mentioned earlier, skeletal muscle tissue serves as the largest reservoir of amino acids in the body and also accounts for the largest mass of protein. There are basically two amino acid pools that are of interest to us: the circulating amino acid pool and the intracellular amino acid pool.

When the body is in a state of starvation (or other catabolic state), amino acids are released from muscle tissue into the bloodstream and used by other body tissues. In contrast, when protein anabolism is necessary, amino acids can be actively transported from the bloodstream into the intracellular space and incorporated into proteins (i.e., new proteins are synthesized).

In addition to the availability of intracellular amino acids, protein synthesis/anabolism is therefore also partly regulated by the transport of amino acids into and out of the cells.

In animals (mainly carnivores), amino acids provide a large amount of energy via the oxidation of amino acids. The oxidation of amino acids to ammonia and their carbon skeletons occurs when excess protein is supplied in the diet or in the presence of starvation, carbohydrate restriction and/or diabetes mellitus.

In humans, ammonia is excreted via the kidneys in the form of urea, while the carbon skeletons of the amino acids are used as substrates of the citric acid cycle for the purpose of energy production. Some people claim that increased kidney stress from high protein intake is against traditional bodybuilding diets, but even protein levels above four grams per kilogram of body weight appear to be safe and harmless for people with healthy kidney function (although this may be a rather exorbitant amount of protein for most exercisers).

Insulin

Insulin is a peptide hormone secreted by the pancreas primarily in response to elevated blood glucose levels (as it upregulates the activity of glucose transport molecules). Unfortunately, thanks to the dramatic rise in type 2 diabetes in the western world, insulin is generally considered the enemy of human physiology as we know it.

However, I can assure you that if your goal is to build a lean and muscular body, you would be well advised to let insulin work its anabolic magic rather than trying to avoid insulin spikes at all costs, as some carbohydrate opponents advocate.

Insulin is one of the most potent anabolic hormones in the human body and induces body-wide anabolism when amino acids are supplied. The key here is that a state of hyperinsulinemia (elevated insulin levels) without concomitant amino acid availability does not appear to increase total body protein synthesis (even though insulin reduces the body-wide rate of protein breakdown in this scenario) (1,2,3).

However, even though insulin reduces body-wide protein breakdown, it does not modulate the ubiquitin system, which is responsible for regulating muscle protein breakdown. Thus, insulin does not specifically reduce muscle protein breakdown (4).

Scientific studies suggest that insulin does not directly alter the transmembrane transport of most amino acids, but instead increases muscle protein synthesis by utilizing the active intracellular amino acid pool (5). The exception to this is amino acids that use sodium-potassium pumps (primarily alanine, leucine and lysine), as insulin causes hyperpolarization of muscle cells by activating these pumps (2).

This suggests that elevated insulin levels in combination with elevated plasma amino acid levels should be quite conducive to promoting muscle protein synthesis. Indeed, this is the reason that patients in a critical state of cachexia (generalized physical decline) often receive an infusion of amino acids and insulin.

Insulin Summary:

All the scientific hoopla can sometimes cause us to lose sight of the big picture. The bottom line of this section is that insulin is indeed a highly anabolic hormone that is conducive to skeletal muscle protein synthesis, but exogenous (external) amino acid delivery is necessary to produce this effect.

As mentioned earlier, a state of hyperinsulinemia (i.e. elevated insulin levels) and hyperaminoacidemia (i.e. elevated plasma amino acid levels) will promote protein synthesis, and what better way to create such a state than to consume protein and carbohydrates in combination.

However, you should be careful not to take the message as "the more insulin the better", which does not seem to be the case in physiological terms. Scientific research seems to suggest that although some insulin will increase the muscle protein synthesis response to a food intake, there is a point of satiety beyond which further increases in insulin levels will not cause a greater increase in protein synthesis (6).

Many people believe that a superfluous boost of fast-acting carbohydrates in combination with whey protein - especially post-workout - is ideal to maximize the muscle protein synthesis response. The reality is that you don't need insulin spikes - a weak and transient insulin response (as seen with low-glycemic carbohydrates) will provide pretty much the same muscle protein synthesis benefits as a rapid massive insulin response.

Insulin-like Growth Factor-1 (IGF-1) & IGF-Binding Protein-3 (IGFBP-3)

As the nomenclature suggests, IGF-1 is a peptide hormone that is quite similar in structure to insulin and has effects on human growth. IGF-1 is mainly produced in the liver following the docking of growth hormones and acts locally in certain tissues or systemically (body-wide). Thus, IGF-1 is a mediator for the effects of growth hormones. IGF-1 is a potent inhibitor of the AKT signaling pathway within cells, which has effects on cell growth and maturation.

For practical purposes, it is important to consider the actions of IGFBP-3 because almost all IGF-1 is bound to one of the 6 protein complexes and IGFBP-3 accounts for 80% of all such binding.

IGF-1 is believed to have similar effects to insulin on protein metabolism due to its ability to bind to and activate the insulin receptor, although the effect of IGF-1 at these receptors is significantly weaker than insulin itself (about 1/10th of the effect) (7).

Thus, it is not surprising that IGF-1 increases protein anabolism in skeletal muscle and throughout the body (8,9). A unique property of IGFBP-3 is that it appears to inhibit skeletal muscle atrophy (i.e., it is anti-catabolic (10).

IGF-1/IGFBP-3 Summary:

Considering that IGF-1/IGFBP-3 are useful in terms of stimulating protein synthesis and maintaining skeletal muscle tissue during periods of muscle wasting/cachexia, the question most are likely asking is "How do I increase circulating levels of these compounds?"

Well, there are several factors that influence the amount of IGF-1/IGFBP-3 (and growth hormones) present in the blood at any given time. These include genetic predisposition, biorhythm, age, training, nutritional status, stress, health status and ethnicity.

Many people assume that an increase in insulin levels may interfere with a subsequent increase in IGF-1 levels, but this is not the case (remember that insulin and IGF-1 are structurally and functionally similar in some ways, but they are produced in different ways). Since an increase in growth hormone levels ultimately leads to the production of IGF-1 (roughly 6 to 8 hours after growth hormone release), it intuitively makes the most sense to focus on increasing endogenous growth hormone levels (which we will look at in the section on growth hormones).

*Quick side note on supplements: Deer Antler Velvet Supplements and other supplements that claim to increase endogenous IGF-1 levels by containing natural IGF-1:

In recent years, some supplement manufacturers have made the claim that products such as Deer Antler Velvet (deer antler extract) can promote muscle growth due to the high levels of IGF-1 naturally contained in these extracts. However, in reality, such products are completely ineffective as IGF-1 is a peptide hormone and is completely destroyed in the digestive tract when taken orally. Apart from that, such complex peptides cannot be absorbed into the body via the digestive tract.

In the second part of this article, we will take a closer look at the influence of growth hormones, androgens, oestrogens, thyroid hormones and stress hormones on protein metabolism.

Source: https://www.muscleandstrength.com/expert-guides/protein-anabolism-catabolism