Carbohydrates are chemical compounds made of differing amounts of carbon, hydrogen and oxygen, as their name suggests carbon (carbo) combined with water (hydrates). These chemical compounds are principally an energy source for the body and are usually termed as a non essential nutrient, however to the bodybuilder they provide a variety of beneficial effects to both training and how the body looks.
Why are carbohydrates beneficial
As stated carbs are nutrients that we can obtain energy from (four kcals per gram), but what’s more important is that the bodies stored carbs (glycogen) are a vital fuel for high intensity activities like weight training. This ability to provide energy during high intensity training sessions will have a two-fold effect upon your workout, but only if the body’s glycogen stores are high enough. The first benefit of having a high glycogen store is that you will be able to maintain higher intensities towards the end of your workouts and therefore provide greater stimulus for growth. The reason that low glycogen levels causes early fatigue, even though you have nearly unlimited potential for energy from fat is related to three factors. Firstly fat is a much slower energy source than carbohydrate metabolism, secondly Carbs act as a primer for fat metabolism (due to the old adage ‘fat burns in a carbohydrate flame’ which relates to the krebs cycle and insufficient levels of oxaloacetate) and lastly the role of glucose and the central nervous system. Since the brain uses blood glucose as a fuel nearly exclusively, low glucose levels will cause central fatigue (in other words the brain can not send as many signals to the muscles).
The second benefit of having higher glycogen levels is that you will recover between workouts faster, meaning you will be able to train harder and more often! It has been reasoned for a while that recovery between workouts is not just about the healing and addition of muscle, but also about refuelling and it has been shown in numerous studies that higher carb diets refuel glycogen levels better than low carb diets.
In addition storing carbs in the muscle will also draw in water to the muscle to be stored as intracellular fluid. This increase in intracellular fluid will make your muscles feel harder as well as increasing the pump when in the gym. The benefits of increased intracellular fluids are not all cosmetic, as an increase in cellular hydration will also promote protein synthesis.
It has been known for a while that carbs cause an insulin response – but only a few realise that this insulin is responsible for helping to drive those vital amino acids into the muscle. Producing a high insulin response causes several changes within the body such as glucogenosis (replacing glycogen stores) and increasing protein synthesis. What’s also beneficial about insulin after a workout is that it opposes catabolic reactions and over a long-term period (eighteen to twenty four hours) can promote growth through mitogenosis and cell replication.
Having a high glycogen store going into a workout will provide more anticatabolic effects than just the ones insulin provides. Higher glycogen stores will cause protein sparring effects, meaning that the protein you eat and your hard-earned muscles won’t be catabolised for energy. During intense workouts glycogen levels fall and to meet the energy demand it will use your muscle’s amino acid to fuel the activity. As glycogen levels fall BC Oxacid dehydrogenase levels rise, which is the enzyme that breaks down the branched chain amino acids within your muscles. So unless you want to use your muscles as energy it would be advisable to make sure you eat a carb rich diet during your bulking phases. The use of an isotonic drink will also aid in preventing high levels of BC Oxacid dehydrogenase.
The rise in BC Oxacid dehydrogenase may also play a part in causing fatigue. BC oxacid dehydrogenase will take up the circulating branched chain amino acids, which in turn allows higher levels of tryptophan in the brain (branched chain amino acids oppose tryptophan through competitive inhibition). These higher levels of tryptophan then go onto convert into 5HT (serotonin), which during exercise may cause central fatigue and therefore decrease your work capacity.
Carbohydrates can be broken down into two categories; simple sugars termed monosaccharides or complex sugars such as disaccharides, trisacchirides, oligiosacchardies and polysaccharides.
Monosaccharide
The most common simple sugars or monosaccharides are glucose, fructose and galactose.
Glucose – glucose is what most carbohydrate gets broken down into to after digestion. It causes a rise in the hormone Insulin which acts as a catalyst for glucose, amino acids and lipids to be taken into the bodies tissues glucose is a major source of energy during exercise especially higher intensities. Glucose is stored within the muscle and liver as glycogen which I a more complex carbohydrate.
Fructose – fructose is found in many sweet fruits maize and honey. Fructose is different from glucose in the fact that it is metabolized differently . Fructose doesn’t need Insulin as it preferentially metabolized within the liver and can either be converted to glucose or into triglycerides. Most natural sources of fructose also come with a high degree of fibre as well, unfortunately many diets are composed of overly processed High fructose corn syrup which doesn’t have this beneficial effect and creates an unnaturally dosage of fructose.
Frctose has been associated with gastrointestinal distress when consumed in great quantities.
Galactose –this is a monosaccharide found in yeast liver and dairy products such as milk.
Oligiosaccharides
These involve thwo or more monosaccharides combined together to create a more complex carbohydrate. The can be classed as either disaccharides (two units), trisacchardies (three units) and tetrasaccharides (four units).
Disaccharides
Sucrose – this is a combination of glucose and fructose units. Sucrose is commonly refered to as table sugar and is derived from cane.
Lactose – this is the sugar found within milk and dairy products and is composed of the monosaccharides glucose and galactose. Some indivudals lack the necessary enzymes to be able to effectively breakdown lactose and suffer with lactose intolerance which is categorized as gas and diarrhea from the undigested carbohydrate fermenting within the gastrointestinal track. Some diary products do not cause this due to either fermentation in the processing of the product or natural enzymes present in the food which aid digestion.
Maltose – this is a disaccharide which is two units of glucose.
Tri and tetrasaccharides
These multiple unit carbohydrates are not very common within most diets but can be found in peas, beans and some root vegetables.
Polysaccharides
These are very long chained carbohydrates and can be broken down into glucose. They are sometimes termed starches. Heating polysaccharides can create smaller compounds which are termed dextrins or glucose polymers.
Amylose - this is a polyglucose molecule that’s structure is composed on long straight links of glucose units. Amylase is a resistant starch which doesn’t break down as easily as amylopectin.
Amylopectin – amylopectin is another polyglucose molecule but instead of being straight like amylase the structure is one composed of a branched chain structure.
Glycemic index, Glycemic load and insulin response
Whilst its important to understand the chemical structure of carbohydrates they don’t paint an exact picture of how they respond in the body when consumed. It was originally thought that the more complex the structure the more slowly the carbohydrate would break down and release into the blood stream. However this is not the case and differing foods increase blood glucose at differing rates. This has lead to a formulation of a scale to rate how quickly a carbohydrate is released and to what extent it causes a rise in blood sugar levels which is termed the glycemic index.
The glycemic index (GI) is derived by comparing a carbohydrate source against a test carbohydrate such as glucose and comparing the rate of blood glucose rise between the two. Glucose is given a rating of 100 and the rise of the carbohydrate source is ranked against this. For instance if a food raised blood glucose levels to 65% of that of glucose the foods score would be 65. figure 6.? Shows a range of glycemic indices for a variety of foods.
(Glycemic index.com 2005)
The problem with the glycemic index is that it gives a value for the same amount of carbohydrate per food which is typically fifty grams of carbohydrate for testing purposes. Whilst this is a good way to standardize testing its not helpful to the individual choosing foods according to glycemic responses. For example it would be very easy to obtain fifty grams of carbohydrates from pizza which have a glycemic indice of thirty, yet oranges have a glycemic index of 48 but would be harder to consume fifty grams of carbohydrate as the carb content is lower per portion and as such would not have the same glycemic consequence.
Considering this a second tool was developed which was called the glycemic load. The glycemic load takes into account both the glycemic quality (GI) of the food as well as the carbohydrate content. The glycemic load can be calculated from the following equation.
GL = GI/100 x Net Carbs
This allows the total blood sugar impact to be calculated from a food specifically from a normal sized portion. A single GL point is considered to be the metabolic equivalent of one gram of glucose.
Even with the glycemic load there is stil problems using this method in that the original principle of the glycemic ratings was to determine the extent of blood sugar rise and the subsequent insulin response related to a given carbohydrate source. However blood glucose is only one factor in determining the insulinotropic effect of a food. The other factors which can effect the rate of insulin release to a given food include specific proteins and fats as well as certain gastrointestinal foods (krezowksi et al 1986)
Considering this there has been a move to try and devise an insulin index instead which rates the insulin response to a meal based upon its energy value. The problem comes with the fact that at present this is still in its infancy and there is limited data compared to glycemic indices.
So with the issues of different carbohydrate and food resonses on raising blood sugar levels, does this have an effect on fat storage? From a direct standpoint it appears no as fat oxidation is not changed significantly between meals of differing GI (Diaz EO et. Al 2006). Does this mean that the GI or the GL isn’t important in weightloss or positive body composition changes – no its just that fat oxidation isn’t the mechanism that’s important. When carbohydrates are eaten insulin is produced and differing GI’s will possibly influence total insulin release but any insulin release is likely to blunt fat oxidation.
As such the influence that GI has on weight loss is probably due to its effect on satiety and how much total calories have been eaten at the meal or later in the day.A second effect which may be more cumulative than the acute effect mentioned above is that the hormonal changes that occur with consumption of lower GI foods may have a greater effect on long term glucose tolerance and therefore promote greater post prandial absorption of foods and allow greater nutritent portioning which relates to where the calories are stored (lean tissue vs fat accumulation).
How much and when
Carbohydrates are not an essential nutrient so when looking at requirements the answer is actually zero. However having said that and the benefits espoused above it would seem that some dietary carbohydrates would aid a hard working bodybuilder directly and in addition would be a carrier for other micronutrients and sources of fiber.
There are several issues with the total amount of carbohydrates a trainee needs in order to register the benefits from the carbohydrates and other consideration in terms of avoiding the negative aspects that carbohydrates can potentially cause.
The first issue is that of carbohydrates offering a protein sparing effect. When there is lack of energy and carbohydrates protein will be used for gluconeogenosis but intakes of around fifty grams of dietary carbohydrates a day appear to prevent this.
One issue is that of having full glycogen levels as this both allows high intensities of work to be carried out for the maximum duration as well as aiding in the decrease of protein utilizarion duiring exercise and the subsequent catabolic state (lemon and mullin 1980). The levels required to maximise glycogen depends upon the metabolism of the individual through the workloads they employ. Different activities usually require different levels of carbohydrate intake due to their overall energy expenditure and the fuel used. The more active an individual is the greater there need for carbohydrates to adequately replace glycogen stores. Typically it is recommended that hard training athletes consume anywhere between six to ten grams of carbohydrates per day depending upon energy needs. For a typical eighty kilogram bodybuilder this would result in 480g to 800g a day if they were to be performing extensively high volumes of training.
However carbohydrate consumption is not as simple as protein consumption in assigning a gram per kilogram recommendation as an individual will respond to carbohydrates differently than another individual due to genetics, prior activity levels and other nutritional and environmental factors that might affect glucose tolerance. When determining an individuals total diet typically the protein content can be worked out as well as the total energy, what ever proportion of energy is left should then be assigned to carbohydrates and fat, the relative contribution of each will be dependant upon their glucose tolerance which can be either done objectively through an oral glucose tolerance test or through subjective analysis of body composition and other signs and symptoms after consuming the given quantities of carbohydrates.
The timing of carbohydrates is as vital as the quantity as post exercise the repletion of glycogen raises from the normal rate of five to six percent up to seven to eight percent (Williams and Devlin 1992) and in addition the fact that the large dosage of carbohydrates does not appear to effect fat oxidation during this period compared to how it does in a rested state (Kimber NE et. al 2003).
Why are carbohydrates beneficial
As stated carbs are nutrients that we can obtain energy from (four kcals per gram), but what’s more important is that the bodies stored carbs (glycogen) are a vital fuel for high intensity activities like weight training. This ability to provide energy during high intensity training sessions will have a two-fold effect upon your workout, but only if the body’s glycogen stores are high enough. The first benefit of having a high glycogen store is that you will be able to maintain higher intensities towards the end of your workouts and therefore provide greater stimulus for growth. The reason that low glycogen levels causes early fatigue, even though you have nearly unlimited potential for energy from fat is related to three factors. Firstly fat is a much slower energy source than carbohydrate metabolism, secondly Carbs act as a primer for fat metabolism (due to the old adage ‘fat burns in a carbohydrate flame’ which relates to the krebs cycle and insufficient levels of oxaloacetate) and lastly the role of glucose and the central nervous system. Since the brain uses blood glucose as a fuel nearly exclusively, low glucose levels will cause central fatigue (in other words the brain can not send as many signals to the muscles).
The second benefit of having higher glycogen levels is that you will recover between workouts faster, meaning you will be able to train harder and more often! It has been reasoned for a while that recovery between workouts is not just about the healing and addition of muscle, but also about refuelling and it has been shown in numerous studies that higher carb diets refuel glycogen levels better than low carb diets.
In addition storing carbs in the muscle will also draw in water to the muscle to be stored as intracellular fluid. This increase in intracellular fluid will make your muscles feel harder as well as increasing the pump when in the gym. The benefits of increased intracellular fluids are not all cosmetic, as an increase in cellular hydration will also promote protein synthesis.
It has been known for a while that carbs cause an insulin response – but only a few realise that this insulin is responsible for helping to drive those vital amino acids into the muscle. Producing a high insulin response causes several changes within the body such as glucogenosis (replacing glycogen stores) and increasing protein synthesis. What’s also beneficial about insulin after a workout is that it opposes catabolic reactions and over a long-term period (eighteen to twenty four hours) can promote growth through mitogenosis and cell replication.
Having a high glycogen store going into a workout will provide more anticatabolic effects than just the ones insulin provides. Higher glycogen stores will cause protein sparring effects, meaning that the protein you eat and your hard-earned muscles won’t be catabolised for energy. During intense workouts glycogen levels fall and to meet the energy demand it will use your muscle’s amino acid to fuel the activity. As glycogen levels fall BC Oxacid dehydrogenase levels rise, which is the enzyme that breaks down the branched chain amino acids within your muscles. So unless you want to use your muscles as energy it would be advisable to make sure you eat a carb rich diet during your bulking phases. The use of an isotonic drink will also aid in preventing high levels of BC Oxacid dehydrogenase.
The rise in BC Oxacid dehydrogenase may also play a part in causing fatigue. BC oxacid dehydrogenase will take up the circulating branched chain amino acids, which in turn allows higher levels of tryptophan in the brain (branched chain amino acids oppose tryptophan through competitive inhibition). These higher levels of tryptophan then go onto convert into 5HT (serotonin), which during exercise may cause central fatigue and therefore decrease your work capacity.
Carbohydrates can be broken down into two categories; simple sugars termed monosaccharides or complex sugars such as disaccharides, trisacchirides, oligiosacchardies and polysaccharides.
Monosaccharide
The most common simple sugars or monosaccharides are glucose, fructose and galactose.
Glucose – glucose is what most carbohydrate gets broken down into to after digestion. It causes a rise in the hormone Insulin which acts as a catalyst for glucose, amino acids and lipids to be taken into the bodies tissues glucose is a major source of energy during exercise especially higher intensities. Glucose is stored within the muscle and liver as glycogen which I a more complex carbohydrate.
Fructose – fructose is found in many sweet fruits maize and honey. Fructose is different from glucose in the fact that it is metabolized differently . Fructose doesn’t need Insulin as it preferentially metabolized within the liver and can either be converted to glucose or into triglycerides. Most natural sources of fructose also come with a high degree of fibre as well, unfortunately many diets are composed of overly processed High fructose corn syrup which doesn’t have this beneficial effect and creates an unnaturally dosage of fructose.
Frctose has been associated with gastrointestinal distress when consumed in great quantities.
Galactose –this is a monosaccharide found in yeast liver and dairy products such as milk.
Oligiosaccharides
These involve thwo or more monosaccharides combined together to create a more complex carbohydrate. The can be classed as either disaccharides (two units), trisacchardies (three units) and tetrasaccharides (four units).
Disaccharides
Sucrose – this is a combination of glucose and fructose units. Sucrose is commonly refered to as table sugar and is derived from cane.
Lactose – this is the sugar found within milk and dairy products and is composed of the monosaccharides glucose and galactose. Some indivudals lack the necessary enzymes to be able to effectively breakdown lactose and suffer with lactose intolerance which is categorized as gas and diarrhea from the undigested carbohydrate fermenting within the gastrointestinal track. Some diary products do not cause this due to either fermentation in the processing of the product or natural enzymes present in the food which aid digestion.
Maltose – this is a disaccharide which is two units of glucose.
Tri and tetrasaccharides
These multiple unit carbohydrates are not very common within most diets but can be found in peas, beans and some root vegetables.
Polysaccharides
These are very long chained carbohydrates and can be broken down into glucose. They are sometimes termed starches. Heating polysaccharides can create smaller compounds which are termed dextrins or glucose polymers.
Amylose - this is a polyglucose molecule that’s structure is composed on long straight links of glucose units. Amylase is a resistant starch which doesn’t break down as easily as amylopectin.
Amylopectin – amylopectin is another polyglucose molecule but instead of being straight like amylase the structure is one composed of a branched chain structure.
Glycemic index, Glycemic load and insulin response
Whilst its important to understand the chemical structure of carbohydrates they don’t paint an exact picture of how they respond in the body when consumed. It was originally thought that the more complex the structure the more slowly the carbohydrate would break down and release into the blood stream. However this is not the case and differing foods increase blood glucose at differing rates. This has lead to a formulation of a scale to rate how quickly a carbohydrate is released and to what extent it causes a rise in blood sugar levels which is termed the glycemic index.
The glycemic index (GI) is derived by comparing a carbohydrate source against a test carbohydrate such as glucose and comparing the rate of blood glucose rise between the two. Glucose is given a rating of 100 and the rise of the carbohydrate source is ranked against this. For instance if a food raised blood glucose levels to 65% of that of glucose the foods score would be 65. figure 6.? Shows a range of glycemic indices for a variety of foods.
Food |
GI |
Peanuts |
14 |
Bean sprouts |
25 |
Grapefruit |
25 |
Pizza |
30 |
Lowfat yogurt |
33 |
Apples |
38 |
Spaghetti |
42 |
Carrots |
47 |
Oranges |
48 |
Bananas |
52 |
Potato chips (crisps) |
54 |
Snickers Bar |
55 |
Brown rice |
55 |
Honey |
55 |
Oatmeal |
58 |
Ice cream |
61 |
Macaroni and cheese |
64 |
Raisins |
64 |
White rice |
64 |
Sugar (sucrose) |
68 |
White bread |
70 |
Watermelon |
72 |
Popcorn |
72 |
Baked potato |
85 |
Glucose |
100 |
(Glycemic index.com 2005)
The problem with the glycemic index is that it gives a value for the same amount of carbohydrate per food which is typically fifty grams of carbohydrate for testing purposes. Whilst this is a good way to standardize testing its not helpful to the individual choosing foods according to glycemic responses. For example it would be very easy to obtain fifty grams of carbohydrates from pizza which have a glycemic indice of thirty, yet oranges have a glycemic index of 48 but would be harder to consume fifty grams of carbohydrate as the carb content is lower per portion and as such would not have the same glycemic consequence.
Considering this a second tool was developed which was called the glycemic load. The glycemic load takes into account both the glycemic quality (GI) of the food as well as the carbohydrate content. The glycemic load can be calculated from the following equation.
GL = GI/100 x Net Carbs
This allows the total blood sugar impact to be calculated from a food specifically from a normal sized portion. A single GL point is considered to be the metabolic equivalent of one gram of glucose.
Even with the glycemic load there is stil problems using this method in that the original principle of the glycemic ratings was to determine the extent of blood sugar rise and the subsequent insulin response related to a given carbohydrate source. However blood glucose is only one factor in determining the insulinotropic effect of a food. The other factors which can effect the rate of insulin release to a given food include specific proteins and fats as well as certain gastrointestinal foods (krezowksi et al 1986)
Considering this there has been a move to try and devise an insulin index instead which rates the insulin response to a meal based upon its energy value. The problem comes with the fact that at present this is still in its infancy and there is limited data compared to glycemic indices.
So with the issues of different carbohydrate and food resonses on raising blood sugar levels, does this have an effect on fat storage? From a direct standpoint it appears no as fat oxidation is not changed significantly between meals of differing GI (Diaz EO et. Al 2006). Does this mean that the GI or the GL isn’t important in weightloss or positive body composition changes – no its just that fat oxidation isn’t the mechanism that’s important. When carbohydrates are eaten insulin is produced and differing GI’s will possibly influence total insulin release but any insulin release is likely to blunt fat oxidation.
As such the influence that GI has on weight loss is probably due to its effect on satiety and how much total calories have been eaten at the meal or later in the day.A second effect which may be more cumulative than the acute effect mentioned above is that the hormonal changes that occur with consumption of lower GI foods may have a greater effect on long term glucose tolerance and therefore promote greater post prandial absorption of foods and allow greater nutritent portioning which relates to where the calories are stored (lean tissue vs fat accumulation).
How much and when
Carbohydrates are not an essential nutrient so when looking at requirements the answer is actually zero. However having said that and the benefits espoused above it would seem that some dietary carbohydrates would aid a hard working bodybuilder directly and in addition would be a carrier for other micronutrients and sources of fiber.
There are several issues with the total amount of carbohydrates a trainee needs in order to register the benefits from the carbohydrates and other consideration in terms of avoiding the negative aspects that carbohydrates can potentially cause.
The first issue is that of carbohydrates offering a protein sparing effect. When there is lack of energy and carbohydrates protein will be used for gluconeogenosis but intakes of around fifty grams of dietary carbohydrates a day appear to prevent this.
One issue is that of having full glycogen levels as this both allows high intensities of work to be carried out for the maximum duration as well as aiding in the decrease of protein utilizarion duiring exercise and the subsequent catabolic state (lemon and mullin 1980). The levels required to maximise glycogen depends upon the metabolism of the individual through the workloads they employ. Different activities usually require different levels of carbohydrate intake due to their overall energy expenditure and the fuel used. The more active an individual is the greater there need for carbohydrates to adequately replace glycogen stores. Typically it is recommended that hard training athletes consume anywhere between six to ten grams of carbohydrates per day depending upon energy needs. For a typical eighty kilogram bodybuilder this would result in 480g to 800g a day if they were to be performing extensively high volumes of training.
However carbohydrate consumption is not as simple as protein consumption in assigning a gram per kilogram recommendation as an individual will respond to carbohydrates differently than another individual due to genetics, prior activity levels and other nutritional and environmental factors that might affect glucose tolerance. When determining an individuals total diet typically the protein content can be worked out as well as the total energy, what ever proportion of energy is left should then be assigned to carbohydrates and fat, the relative contribution of each will be dependant upon their glucose tolerance which can be either done objectively through an oral glucose tolerance test or through subjective analysis of body composition and other signs and symptoms after consuming the given quantities of carbohydrates.
The timing of carbohydrates is as vital as the quantity as post exercise the repletion of glycogen raises from the normal rate of five to six percent up to seven to eight percent (Williams and Devlin 1992) and in addition the fact that the large dosage of carbohydrates does not appear to effect fat oxidation during this period compared to how it does in a rested state (Kimber NE et. al 2003).
