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Carbohydrate Science and Metabolism

Carbohydrate Science and MetabolismLesson Outcomes:

  • Know the important roles that Carbohydrate (CHO) plays in human physiology
  • Be familiar with guidelines for CHO intake
  • Understand differences between types of CHO
  • Describe ways to replenish glycogen with CHO intake timing

Take all that you believe you know about carbohydrate and place it to the side for this lesson.  For our physically active clients, diets rich in diverse carbohydrate types can help to replenish muscle glycogen levels, enhancing recovery.  Carbohydrate intake will also increase performance and slow down the onset of fatigue for exercise bouts lasting longer than an hour.  For active people, a diet high enough in carbohydrate to replace muscle glycogen used during exercise makes sense, but we must learn more about why.  Unfortunately, there are many misconceptions among active people with respect to the issue of consuming the right levels of carbohydrate. Optimum dietary carbohydrate levels depend on total energy intake, body metrics (size), overall health status, and the individual’s duration, intensity, frequency, and type of exercise.  And trainers and coaches alike serve the needs of their clients and impact their own success through the dietary intakes of their clients.   Your reputation is on the line to deliver your client results.  You cannot do this without a fundamental level of understanding related to carbohydrate

Carbohydrates

Carbohydrates fulfill several roles in human physiology. The body’s priority is to make sure that the brain has sufficient glucose to function and to provide energy for muscular work. Without the proper carbohydrate intake, the ability to make glucose can still occur, but is derived differently than when glucose is taken up or absorbed and assimilated from ingesting carbohydrates. The usable form of glucose for muscular work is glycogen. In fact, carbohydrate stores are retained in both muscle and liver tissues as glycogen. By design, glycogen can provide energy for PA over an extended period.

A basic overview of carbohydrate facts:

  • Adults need 45-65% percent of their total calories from
  • Athletes training at higher levels of intensity (approx. 70% HRmax) need to consume 5 to 7g/kg/BW per day.
  • Focus on fiber
  • Recommend whole-grain carbohydrates for all meals, except during and post-workout.
  • Consuming a variety of bright, colorful fruits and vegetables is recommended.
  • Consume high-glycemic, rapidly absorbed simple carbohydrates after a workout.

Because the body can make glucose from non-carbohydrate sources (gluconeogenesis), carbohydrates are not considered essential or non-essential. If there is not enough carbohydrate converted to glucose for energy, the body will tap into other systems to make this substance – THAT’S how important glucose and

carbohydrates are to our functionality. As an example, after fasting when carbohydrates have been restricted, glucose is made from fats and proteins – even if not in the GI tubing at that time. Again, a relatively efficient design that works to provide a stable and constant source of energy for the body to then use.

A carbohydrate is one type of natural organic substance that includes sugars, starches, and cellulose. The molecular composition of carbohydrates is formed in combinations of carbon, hydrogen and water. Carbohydrates are often isomers – meaning, they have identical atomic compositions but vary in their structure. As examples, fructose, galactose, and glucose are isomers with the chemical formula C6H120.

You can then see that chemical formulations go beyond the scope of what you will most likely need to know to understand carbohydrate consumption,  but  the  most  common  way to classify carbohydrates is to separate them into four major  groups: saccharides,  monosaccharides, oligosaccharides and polysaccharides.

Monosaccharides (simple sugars) are molecules that usually contain five or six carbon atoms. The three most common monosaccharide carbohydrate types include glucose (also called dextrose, fructose  or the sugar in fruit), and galactose. Glucose is included in the group of the most common carbohydrates – disaccharides, sucrose, and lactose, and is also the sole structural component of the polysaccharides cellulose, starch and glycogen grouping. Galactose is a common member of the oligosaccharide and polysaccharide group (e.g., agar, carrageenan), and is even found in some lipids (glycolipids) located in the brain and in nerve tissues.

Disaccharides are different in their molecular structure as they are composed of two simple sugar molecules and are therefore sometimes referred to as “double sugars.” An example would be the disaccharide sucrose, which contains one molecule of glucose and one molecule of fructose. Other disaccharide carbs include lactose (milk sugar) and maltose.

Oligosaccharides are carbohydrates with three to six monosaccharide units and are less common. Many oligosaccharides are the result of breaking down polysaccharides. Most naturally occurring oligosaccharides are found in plant foods and include raffinose (a trisaccharide) consisting of melibiose (galactose and glucose) and fructose.

Polysaccharides, including cellulose, starch and glycogen, are much larger molecules and comprise up to 10,000 monosaccharides. Most of the stored carbohydrates from nature occur in the form of polysaccharides. For example, glycogen consists of a complex chain of glucose molecules. The two most well-known polysaccharides are cellulose and starch. Cellulose – the basic structural material in plants – contains more than 3,000 glucose molecules. We consume cellulose in the form of insoluble dietary fiber. Starch refers to a class of plant-based polysaccharides made up of units of glucose. Starches typically comprise a combination of two substances: amylose and amylopectin.

Remember what you’ve learned about digestion – humans metabolize starch in our digestive system in stages. First, digestive enzymes called amylases convert the starch into maltose. As maltose is absorbed through the walls of the intestine, it is hydrolyzed to glucose and distributed to cells and muscles for energy or stored as glycogen or fat.

Even though carbohydrate intake is vital, a lot of popular diets used by your clients may try to restrict carbohydrate intake. In reality, the body needs carbohydrates, especially for PA. What needs to be mastered by the client is: 1) understanding the differences between carbohydrate types, and 2) the timing of their intake. Cutting carbohydrates is extremely unwise since it is a vital source of energy, fiber and vitamin C. If this compound is cut from the diet, an entire macronutrient is being eliminated – and as it happens, this is the macronutrient that is needed in the largest percent by volume.

Dietary guidelines for carbohydrate consumption expressed as a ratio of the total, are pretty standard across the board. The most credible sources put this percent of intake at about 45 to 65% of all daily food intake and calories from carbohydrates. The non-active or more sedentary individual would be consuming closer to the 45% mark, while those engaged in PA will have an eating plan that increases the percent up to the 65% level. Therefore, the differences are mainly seen in terms of how active the individual is or if the goal includes overall weight loss or gain.

Carbohydrate Types:  Simple Carbohydrate

There is a tendency in the fitness industry to discourage simple carbs, as they tend to alter energy levels acutely and cannot provide enough fuel for people who are active. But there is a proper time and circumstance for taking in simple carbohydrates. Still, their intake should be understood and should be a small part of the overall carbohydrate intake due to the relatively small amount of benefit to the client (energy and nutrient concerns).

Simple carbohydrates are known as monosaccharides and include any of the compounds that end in “ose” – fructose, galactose, and glucose are a few.

Again, based on the molecular bonds of carbohydrate molecules, they are considered either mono- or disaccharides. Disaccharides are simply the pairing of two monosaccharides and include sucrose, lactose, and maltose.

Your client is not expected to know this information – but you are – and part of your responsibility includes coaching your client to understand carbohydrates in their simple form.  This will be vital to their success, since carbohydrates determine or influence everything from anabolic reactions to energy supplies.

Simple carbohydrates are rapidly converted to glucose, so there is no real chance for the body to use them for sustainable energy, as in a bout of PA. Be sure that your client knows all of the terminology shared by the food industry to indicate simple carbohydrates in consumables.

Complex Carbohydrate

Complex carbohydrates are derived from plants that contain both starch and dietary fiber. This includes vegetables, potatoes, dried beans, grains, and fruits. Animal products contain little, if any, carbohydrates.

Complex carbohydrates should be the greatest part of the daily intake for your client – at the right time! The energy from these complex carbohydrate molecules is more of a slow, steady burn, and can prevent peaks and valleys in clients’ energy profiles. Insulin secretion is also more controlled in the presence of complex carbohydrates. All of this is in addition to the health benefits of consuming less-refined foods, as in whole grains due to the increased fiber and the effects on heart health and certain cancers.

Complex carbohydrates are similar to their simple counterpart in one main way – they are broken down into glucose and then eventually are used to provide energy for human function and performance. Where the two are different is also significant; the complex bonds of multiple molecules linked together means that it is a slower process within the body to make glucose, and to then digest them properly. Many times this will help your client feel as if they are fuller for a longer period of time compared to the ingestion of simple carbohydrates.

More on Complex Carbohydrates – Fiber

Rarely, you will find a client who consumes enough fiber. Furthermore, not many of your clients will know the amount of fiber recommended as a daily allowance. Do you know what the intake for fiber is?

To encourage the intake and consumption of more fiber in clients’ diets, coach them to understand the health benefits of doing so. This includes lowering the risk for certain diseases, including heart disease. Fiber consumption in the proper amount also helps lower other risk factors tied to diseased states like diabetes, obesity, and disorders of the GI tract.

Fiber will also act to slow how food is digested after being consumed. For your client, this may mean that they now can have enough energy to complete their PA goals each day. This will also help to provide more energy during a bout of PA, due to the slower digestion seen when complex carbohydrates are eaten in the form of fiber.

Fiber can be further broken down into different categories or classifications.

Functional fiber

This classification of fiber has specific purposes in the body, including the feeling of being fuller, longer. Other benefits include improved control over insulin secretion and more stable blood sugar levels. Motility and absorption are also influenced positively by fiber intake, meaning that fiber will help to prevent constipation while working to reduce dietary fat and cholesterol absorption in the GI tract.

This group, functional fiber, includes the following:

  • Psyllium
  • Pectin
  • Cellulose
  • Seeds and plant gums

 

These items can frequently be found in:

  • Oats (oatmeal or oat bran cereals)
  • Wheat (whole wheat)
  • Vegetables
  • Fruits
  • Beans (dried)

Carbohydrate Functions in the Body

Carbohydrate serves a vital role in human physiology and as a primary source of energy; the majority of our diet needs to come from carbohydrate.  Carbohydrate provides the substrate (glucose) needed for glycogen replacement.   Carbohydrate intake influences blood glucose levels and helps prevent premature fatigue if consumed during exercise.  Clients who perform moderate training are encouraged to eat carbohydrate diets that supply ~5 to 7 g carbohydrate per kilogram body weight and up to 10 g carbohydrate per kilogram body weight during periods of heavy training.  Athletes should also use carbohydrate-containing sport beverages and foods to supplement their diet as needed.

We can classify dietary carbohydrates in a few different ways.  This includes the type of carbohydrate in foods consumed, the level of processing of the food, and the glucose or glycemic responses to the carbohydrate within the body.  In the past, carbohydrate-containing foods comprising long complex chains of sugars linked together were typically referred to as complex carbohydrates.

Initially, it was thought that these long chains of sugar digested more slowly than the simple carbohydrates described next. We now know this is not true and therefore the term “complex carbohydrate” only refers to the structure of the carbohydrate but is not related to digestive properties.  In the field of nutrition, the term “complex carbohydrate” is generally used for carbohydrate-containing foods, including whole grains (breads, cereals, pasta), and legumes (beans, peas, lentils).  When you hear complex carbohydrate, it normally refers to digestible carbohydrate in these foods being starch.

Carbohydrates from processed foods (sweetened cereals, breakfast bars) or foods high in sugar (candy, sodas, and desserts) are typically termed simple carbohydrates.  These foods are primarily glucose, sucrose, fructose, and high-fructose corn syrup and as such are generally lower in vitamins, minerals, and fiber totals, provided they have not been fortified in processing.

Complex carbohydrates are usually comprised of a complex chemical structure; they are less processed, and normally contain more nutrients and fiber than simple carbohydrates. Referring to carbohydrates as “simple” or “complex” doesn’t tell the whole story, though – as research shows that the glycemic responses to both simple and complex carbohydrate foods can be very different.  Some complex carbohydrates can be hydrolyzed and absorbed as quickly as simple sugars.

Instead, we now see that carbohydrates are classified as foods resulting in a high, moderate, or low glycemic response. Foods that produce a high glycemic response—a large and rapid rise in blood glucose and insulin levels –will increase muscle glycogen more than foods that produce a low glycemic response

Foods classified as simple carbohydrates are made up of mono-, di, and oligosaccharides.  Most of these carbohydrates are present organically in foods, while others – such as high-fructose corn syrup (HFCS), are produced commercially for use in processed foods. The rate at which the different forms of carbohydrate are absorbed and oxidized varies within each of us and your client is no exception.

Carbohydrate Metabolism

The human body requires carbohydrate intake as a fuel source for basic physiological function and this includes physical activity as well. The amount of carbohydrate needed will depend on the frequency, intensity, duration, and type of the exercise and the environmental conditions in which the exercise is performed.  During exercise, carbohydrate used for work can come from any of the following sources:

  • Endogenous production of glucose by the liver (gluconeogenesis)
  • Blood glucose
  • Muscle and liver glycogen stores
  • Carbohydrate consumed during exercise (e.g., exogenous carbohydrate: sports drinks, etc.)

Endogenous Glucose Production During Exercise

The substrates for gluconeogenesis during exercise are lactate, alanine, glycerol, and pyruvate.  These substrates come mainly from skeletal muscle, with small amounts of glycerol coming from adipose cells. These substrates are transported to the liver, where they are used for glucose production.  This is a very complex pathway to making glucose in the liver.

The primary source of lactate during exercise results from the metabolism of glucose to lactate.  This process, called glycolysis, is active in both the working and nonworking muscles.  Lactate is either transported to the liver for glucose production or it might be used directly by cells as an energy source. As glycogen is depleted in a muscle, non-active muscles can also free up some of their stored carbohydrate after lactate is released.

A second major gluconeogenic precursor is alanine. Alanine is the primary amino acid released by working muscle during exercise.   In lab studies, the rate of alanine’s presence was seen to increase 60 to 95% after 40 minutes of strenuous exercise.  Alanine, released from the breakdown of amino acids in the muscles, is synthesized as nitrogen and can then combine with pyruvate for other reactions resulting in – you guessed it… more glucose.   Once pyruvate is returned to the liver, it can be used as a gluconeogenic substrate.  The resulting nitrogen is converted into urea and eliminated through the kidneys.

Another gluconeogenic precursor used in the liver is glycerol,   a three-carbon backbone of triglyceride. When adipose tissue or muscle triglycerides are broken down, the result is three fatty acids and glycerol.  Fatty acids from adipose tissue are then able to be transported to skeletal muscles for energy production, but the glycerol is transported to the liver after being broken down in the process of gluconeogenesis. During prolonged exercise, especially when no exogenous carbohydrate is available or consumed, gluconeogenesis becomes a major source of glucose for active (working) skeletal muscles.  In fact, nearly 60% of glucose made available in longer duration events (greater than three hours) is a result of the uptake of lactate, pyruvate, and glycerol by the liver.

The rate of endogenous glucose production is changed if exogenous carbohydrate is available (consumed) by your client while they are exercising.  When the body has a way to supplement carbohydrate during times of need (exercise), the body can use this exogenous carbohydrate as an energy source.   Therefore, the need to synthesize new glucose from gluconeogenic precursors – such as protein – is reduced.

Carbohydrate Metabolism and Hormonal Control

During exercise, hormonal changes in the body signal the break down stored energy fuel.  This fuel is then used by skeletal muscles for energy. These hormonal responses are unique for each of us and depend on many different factors including the intensity and duration of the exercise, the individual’s level of physical fitness, and the client’s overall health.  Generally, clients with rigorous training regimens are likely to have different responses than someone who does not do regular fitness training or physical activity.

Two hormones of note – norepinephrine and epinephrine – increase their concentration in the circulatory system within minutes of the onset of physical activity.  These hormones stimulate the breakdown of stored fat and carbohydrate and in doing so, make these fuels available to the working muscles. Insulin levels decrease or are maintained at a low concentration during exercise yet glucagon levels increase. Glucagon stimulates glycogenolysis and gluconeogenesis and both metabolic processes help maintain blood glucose levels.   This is accomplished by increasing the release of glucose into the blood. Exercise is also believed to increase the sensitivity of skeletal muscle to the action of insulin.

Hormonal changes during exercise are aimed at creating an optimal environment for the breakdown and oxidation of both fat and carbohydrate for energy.  Interestingly, the acute hormonal response to exercise is similar to what is observed with fasting states.   In both exercise and fasting, the body still has to provide energy to working muscles from the body’s stored energy reserves, requiring that energy be broken down and provided to cells and tissues that require it.

The body’s carbohydrate reserves are primarily in liver and muscle glycogen. Glycogen concentrations are highest in the liver, ranging from 60 to 120 g (250-500 kcal), depending on the time of day and the amount of carbohydrate in the last meal consumed. During sleep, liver glycogen plays a major role in maintaining blood glucose levels throughout the night. Consuming breakfast is the best way to replenish blood glucose after sleep.

The amount of carbohydrate stored in muscle is lower than that in the liver.  Muscle tissue typically accounts for 20 to 30% of total body weight and the amount of glycogen stored in the muscle can range from roughly 300 to 400 g (1200-1600 kcal), depending on your client’s size. Muscle glycogen levels can be increased when certain conditions require doing so.  This is done by consuming a meal high in carbohydrate after exercise has depleted the stores of muscle glycogen.

Our bodies naturally maintain glycogen stores within a desirable range.  This means that the body balances carbohydrate oxidation to carbohydrate intake as a form of homeostasis.  After consuming a meal, about 25% of carbohydrate consumed is converted to liver glycogen; about 30-50% is converted to muscle glycogen.  The remainder is left to be oxidized for energy needed later.

Use of muscle glycogen during exercise will depend on several factors, including the amount of glycogen available before exercise begins, the exercise intensity and duration, the environmental conditions, and whether endogenous carbohydrate is consumed.

A client with higher glycogen stores at the beginning of a workout will fatigue later than one who begins the event with lower glycogen stores.  It’s also important to acknowledge that depletion of muscle glycogen is not the only factor involved with the onset of fatigue during exercise.  Physiological, psychological, and environmental factors also affect fatigue.

Dietary Carbohydrate Intakes of Active Individuals

Physically active people will usually have carbohydrate intakes similar to those who are generally inactive; 45 to 55% of total energy generally comes from carbohydrate.  For active people these intakes may only be adequate to meet the carbohydrate demands of exercise for 1 h or less per day. These carbohydrate intake levels may be too low, however, for an endurance athlete who performs intense training most days of the week.  For this client, glycogen stores need to be replenished strategically – and acutely.

The positive relationship between dietary carbohydrate intake, muscle glycogen levels, and the ability to perform endurance exercise is now  well known through documented research.   Most personal trainers, athletic trainers, and sport dietitians believe that consuming a high-carbohydrate diet during periods of intense training is a best practice.

While these general recommendations are similar to those for the general population (45-65% of energy from carbohydrate), most clients will want dietary and carbohydrate recommendations specific for the day of training or competition.  This also affects the eating habits in the hours immediately before training or competition.

Pre-Exercise Meals

For active clients, trainers also need to focus on what our clients eat between training sessions.  This is to encourage glycogen synthesis, to supply the body with glucose for use during exercise, and to minimize fatigue during exercise.  As a goal of a pre-exercise meal, any foods consumed just before competition can become important for energy production.

For clients who believe in training after a period of fasting (as in, overnight), lower liver glycogen levels need to be replenished and a pre-exercise meal helps liver glycogen production and provides the body with additional carbohydrate to help prevent or delay the onset of fatigue while training. Consumption of carbohydrate before exercise is also believed to improve performance for individuals who may not have fueled their body in preparation of training or competition.

Researchers have also examined whether the form of the carbohydrate fed (food vs. beverage) alters blood glucose responses and exercise performance. A number of studies have now addressed these issues and have shown that carbohydrate feeding immediately (30-60 min) before exercise has no adverse effect on performance or perceived exertion.

The type of fiber in this oat bran may help protect your client from diseases of the GI tract, among them – diverticulosis and colon cancer.

Carbohydrate Intake During Physical Activity

Since a client will fatigue when they engage in moderate exercise of long duration, a decrease in blood glucose and a depletion of muscle and liver glycogen stores is likely.   Once used, there is an increased need for the liver to provide the glucose needed to support exercise.

Consuming exogenous carbohydrate can delay fatigue but it will not prevent it entirely. Researchers have suggested that they see exogenous carbohydrates consumed during exercise to reduce fatigue and improve performance through a combination of events, including the sparing of muscle glycogen, maintaining blood glucose, and oxidation of carbohydrate and synthesizing glycogen during low-intensity exercise.

Naturally, these events may vary, depending on the intensity and duration of the exercise bout. Individual responses to exogenous carbohydrate during exercise depend on the nutritional and health status of a client when they begin their exercise routine.

Practical Guidelines for Carbohydrate Intake  During Exercise

The following guidelines may be helpful to active individuals and athletes who consume carbohydrate during exercise.

  • People respond differently to various types of carbohydrate foods or drinks. To avoid unexpected gastrointestinal disturbances during competition, athletes should use the carbohydrate supplement during training that they will use during competition.
  • Athletes should ingest carbohydrate early in an exercise session to prevent the decrease in blood glucose often seen during endurance events. This practice is especially helpful for those who come into an exercise event with poor glycogen stores (e.g., people who are involved in very heavy training or who have followed a low-kilocalorie or a high-fat diet).
  • Sport drinks or other carbohydrate-containing drinks should have a concentration of 6 to 8% carbohydrate (60-80 g/1000 mL). Drinks with a higher concentration of carbohydrate are not absorbed well and do not replace lost fluids during exercise as efficiently. An additional advantage to sport drinks is that they contain sodium, which helps in the absorption of carbohydrate across the gut mucosa and helps prevent dehydration and hyponatremia.

Athletes should drink enough fluid to provide between 40 and 75 g of carbohydrate per hour. Exercise events of long duration or during extreme temperatures may require higher fluid and carbohydrate intakes.

Carbohydrate Intake – Post-exercise

After an exercise session, it is important to replenish muscle glycogen stores – and for some who have a higher frequency of training – refuel the body for the next exercise event. In general, a client who has approximately 24 hours or more before the next activity can replenish glycogen stores more easily than if they exercise sooner. For exercise enthusiasts, it is rare for 24 hours to pass between exercise sessions and therefore post-exercise feeding is much more critical. The types and amounts of food consumed – paired with the timing of the meals after exercise – depend somewhat on when the next exercise bout will occur.  Apart from refueling the body, post-exercise feeding should provide sufficient energy and nutrients to repair muscle tissues broken down by muscular work  from resistance training.   It also needs to include fluids to rehydrate our client’s body.

Determining Overall Carbohydrate Intake for Individuals

Although it is frequently recommended that athletes follow an eating plan containing 55% (or for some, up to 65%) of the energy from carbohydrate, this might be unrealistic for some individuals. Making carbohydrate recommendations based on grams of carbohydrate per kilogram body weight may be more accurate, easier, and a more realistic approach. The total amount of carbohydrate consumed in a diet containing 65% of its energy from carbohydrate varies dramatically with total calories consumed. For many male athletes this level of carbohydrate intake would be a more realistic and achievable goal and would easily replace muscle glycogen during heavy training periods. For many female athletes, who typically report consuming 2,200 to 2,500 kcal/day, it is almost impossible to consume the 500 to 600 g of carbohydrate per day frequently recommended for adequate glycogen replacement in men.  Athletes who are dieting might be able to consume a high-carbohydrate diet (60-70% of energy from carbohydrate), but the amount of carbohydrate per kilogram of body weight will be disproportionately low. The goal is to prevent premature fatigue during prolonged endurance exercise and to adequately replace muscle glycogen daily during periods of intense exercise training. Carbohydrate recommendations are more accurate when based on grams of carbohydrate per kilogram body weight than on percentage of total energy from carbohydrate.

Practical Guidelines for Carbohydrate Replenishment

The following recommendations on post-exercise carbohydrate consumption assume that the client is in training (or competition) and therefore, requires maximum glycogen replacement.

Over a two-hour period, feed ~5 to 7 g of carbohydrate per kilogram body weight for individuals doing moderate training and up to 10 g carbohydrate per kilogram body weight for individuals doing heavy training routines. Male athletes consuming more than 3,500 kcal/ day should be able to consume 500 to 600 g carbohydrate per day. Smaller individuals or those who need fewer calories will realize how difficult it is to consume this amount post-exercise. A diet providing 6 to 8 g/kg body weight should be adequate for glycogen replacement for these people.

  • Provide a carbohydrate replacement beverage containing 40 to 80 g of carbohydrate per serving immediately after exercise if athletes are eating self-selected diets, are unable to eat within two hours, or do not feel hungry after strenuous exercise. The beverage should provide enough additional carbohydrate to replace muscle glycogen when added to the carbohydrate and protein consumed in the self-selected diet. This recommendation is very useful to coaches or trainers who have little control over athletes’ diets, since it promotes adequate glycogen replacement even if athletes have poor diets.
  • Consider individual athletes’ dietary preferences. You can set carbohydrate recommendations and goals, but they will not be achieved if they do not fit well into an individual’s daily diet. Your recommendations must be acceptable in relation to the athletes’ time and financial constraints as well as their cooking abilities. Great diet plans are useless if they are not implemented.
  • If you need a more specific post-exercise recommendation, try the following: suggest that clients consume 1.0 to 1.2 g of carbohydrate per kilogram body weight the first 30 to 60 min after exercise. For a 176-pound (80 kg) man, this would be approximately 80 to 96 g of carbohydrate; for a 121-pouond (55 kg) woman, it would be 55 to 66 g.

Summary

Carbohydrate is an important component in the eating plans of active individuals because it is required for glycogen synthesis and for the maintenance of blood glucose levels during exercise. During intense daily exercise training, the client food intake must include levels of carbohydrate to match their kcal expenditure and for clients who have a goal to lose weight, a kcal deficit still has to be maintained.  This is challenging for both the client and the trainer or coach.

Learning specifics pertaining to carbohydrate, glucose, and energy will help inform your suggestions to clients.

The exact level of carbohydrate intake will depend on the client, their level of energy intake, body size, and goal(s).  In addition, carbohydrate consumption before and during exercise will help improve performance and prevent fatigue, especially in endurance events lasting longer than 60 minutes. During exercise, carbohydrate-containing drinks can provide optimal gastric emptying and absorption.

You have choices for nutrition education and certifications:

NESTA Lifestyle and Weight Management Specialist Certification
NESTA Sports Nutrition Specialist Certification
NESTA Fitness Nutrition Coach Certification

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