Carbohydrates: Role and Function in Fitness and Strength Training

Geschatte leestijd: 28 minutenCarbohydrates, or sugars, play a very important role in metabolism. They are nowadays the main source of fuel for the body. It is therefore important that the body continuously has enough sugar available to provide it with energy. Insulin plays an important regulatory role in this process to prevent too much or too little sugar from circulating in the blood.

Table of Contents

• Different types of sugars
• Slow carbohydrates and fast carbohydrates
• Dietary fibers
• Glucose
• Glycemic index and glycemic load
• Glycemic load
• Insulin
• Blood sugar
• The influence of insulin on “blood sugar”, muscle growth and increase in body fat
• Liver and muscles: Absorb more glucose
• Increase “glycogenesis”
• Lower “gluconeogenesis”
• Increase protein synthesis in muscles (muscle growth!)
• Increase synthesis of fatty acids, “lipogenesis” (increase in fat!)
• From carbohydrates to fat?
• Main tank and reserve tank
• How many carbohydrates to eat?
• Too many carbohydrates nowadays?
• Diabetes in short
• Diabetes, strength training and muscle growth
• “Strength training reduces the risk of diabetes”
• “Strength training as a treatment for diabetes (type II)”
• “Bring on the heavy weights!”
• The effect of diabetes on strength training
• Dividing carbohydrates
• Especially slow carbohydrates
• When fast sugars?
• Hyper
• Important for the exercising diabetic!
• Go see the doctor!
• Diabetes and protein supplements
• Diabetes and the kidneys
• Proteins and the kidneys
• Insulin as doping
• Insulin dangerous as doping
• Types of carbohydrates
• “Hydrate of carbon”
• The function of carbohydrates in nature
• Glucose
• Different types of carbohydrates
• Carbohydrates from one or more saccharides (simple and complex)
• The number of (chains of) saccharides forming the carbohydrate.
• Digestible and non-digestible carbohydrates
• Number of carbon atoms
• Isomers Alpha and beta (α & β), L and D
• Summary

Different Types of Sugars

There are many different types of carbohydrates, also known as sugars or saccharides. These are molecules formed by a chain of oxygen, hydrogen, and carbon atoms.

There are sugars that consist of:

• One chain: monosaccharides. For example, glucose, fructose, and galactose.
• Two chains: disaccharides. For example, lactose (glucose+galactose).
• A few chains (3 to 9): oligosaccharides. For example, raffinose (found in beans, consisting of one galactose, one glucose, and one fructose chain).
• Many chains: polysaccharides. For example, starch (multiple glucose chains).

As sources in nature, you can think of the carbohydrate lactose found in milk, which is a disaccharide composed of the monosaccharides glucose and galactose. Another example is starch, such as in potatoes, which is a polysaccharide composed of multiple glucose chains. A final example is sucrose (or “saccharose”) which is extracted from sugar beets and is known as the table sugar we use to sweeten our food. Sucrose is a disaccharide composed of a glucose and a fructose chain.

Slow Carbohydrates and Fast Carbohydrates

You can distinguish carbohydrates from each other in various ways, but in practice, the speed at which they cause an increased blood sugar level is the most important difference for most people.

There is also a difference in chemical composition. The above-mentioned mono- and disaccharides are called “simple carbohydrates” and the oligo- and polysaccharides “complex carbohydrates.”

Confusingly, the term “simple carbohydrates” is also used to indicate monosaccharides, which are distinguished from “complex carbohydrates,” namely the di-, oligo-, and polysaccharides. Because it mainly concerns the rate of absorption, I find the classification simple/complex more convenient because both mono- and disaccharides are quickly digestible.

The simple carbohydrates are absorbed more quickly in the intestines and are therefore often called “fast carbohydrates,” while the complex carbohydrates, which are absorbed more slowly, are called “slow carbohydrates.”

In short, you can say that complex, slow carbohydrates are always preferred except when there is an immediate need for an increase in blood sugar level (see further).

Dietary Fibers

Then there is the difference between “digestible” (or glycemic) and “non-digestible” (or non-glycemic) carbohydrates. Digestible carbohydrates usually include various sugars and starch. “Non-digestible” carbohydrates refer to dietary fibers. The term “non-digestible” refers to the fact that these cannot be absorbed and broken down into glucose in the small intestine like digestible carbohydrates.

Non-digestible carbohydrates are dietary fibers. These are broken down in the large intestine by the intestinal flora (bacteria). The term “non-digestible” is not entirely accurate. These dietary fibers can also be divided into digestible or non-digestible. The digestible fibers can be partially digested by fermentation and thus provide energy. Moreover, digestible fibers have been shown to have a beneficial effect in preventing diabetes (36-40).

Glucose

In the gastrointestinal tract, di-, poly-, and oligosaccharides are broken down by enzymes (called carbohydrases) into the monosaccharides glucose, fructose, and galactose. Only glucose can be transported through the intestinal wall into the bloodstream. Fructose and galactose are therefore converted into glucose in the liver by specific enzymes. In the first article about milk, I already wrote about the problems and lactose intolerance when the body does not have enough enzymes to convert galactose into glucose.

Once broken down or converted, glucose can be absorbed into the bloodstream. The amount of glucose in the bloodstream must be closely regulated. Especially the brain consumes a lot of the energy that glucose provides. Both too much (hyper) and too little glucose (hypo) can lead to dangerous side effects ranging from headaches to, in severe cases, a (potentially fatal) coma. To ensure that the amount of glucose in the blood (“blood sugar level”) does not rise too high, or later drops too low when carbohydrates have not been eaten for too long, the body relies on insulin.

Glycemic Index and Glycemic Load

Carbohydrates thus cause an increase in the amount of glucose in the blood. How quickly this happens depends on the type of carbohydrate and the amount eaten. The glycemic index is an indicator of the speed at which certain carbohydrates raise blood sugar levels compared to glucose itself. Glucose therefore has a score of 100 as a benchmark. Besides, you can see a table with the glycemic index of some sugars, but every product with digestible carbohydrates has a glycemic index.

The glycemic index was developed in Canada in the early 1980s to determine which foods are suitable for diabetics (2).

However, the glycemic index (GI) has limitations:

• The speed at which the consumption of certain carbohydrates leads to an increase in the amount of glucose in the blood can vary depending on the cooking method. For example, the same type of potato can have a moderate GI (56-69) or a high one (70 and higher) (3,4).
• The speed at which the consumption of certain carbohydrates leads to an increase in the amount of glucose in the blood can vary depending on the individual due to differences in insulin sensitivity (see further). Moreover, it can vary from day to day in the same person depending on the blood sugar levels before carbohydrate intake (4).
• The glycemic index does not consider the rise in blood sugar levels longer than two hours after intake (4).
• The glycemic index does not take into account the amount of carbohydrates consumed (see glycemic load).

As you can see, the glycemic index of carbohydrates is not a fixed value. It is only an indication of how quickly a certain product can raise blood sugar levels.

Glycemic Load

As mentioned, the glycemic index does not take into account the quantity of carbohydrates eaten. The glycemic load does. The glycemic load is: The number of grams of digestible carbohydrates in the food multiplied by the GI of that type of carbohydrate, divided by 100.

A good example often given in this regard is watermelon. Watermelon has a glycemic index of 72 (= high). However, watermelon contains only 7.5 grams of digestible carbohydrates (sugars). So, the glycemic load is: (7.5 X 72) / 100 = 5.4 (= low).

For glycemic load, you can consider anything above 20 as high, 11-19 as average, and below 10 as low.

The glycemic index of watermelon, 72, is high. However, the glycemic load, 5.4, is low. A banana has a glycemic index of 52. If you only looked at this, you would judge that a banana raises blood sugar levels more slowly than a comparable amount of watermelon. However, looking at the glycemic load (18.8 X 52 /100 = 9.8), this provides a better picture, clearly showing that the banana raises blood sugar levels faster.

Insulin

Insulin regulates the amount of glucose in the blood. The name insulin comes from the discoverer Paul Langerhans (1847 -1888). This German, then a medical student, discovered the cells in the pancreas that release various hormonal substances, including insulin. These cells were called the islets of Langerhans because they were clustered together (Latin for island = insula). It was only after his death that the function of insulin became known.

Insulin is a polypeptide hormone. Peptides are small chains of amino acids, polypeptides are formed by several of these peptides. So, insulin, being composed of chains of amino acids, is a protein. Proteins eaten are broken down in the stomach before reaching the blood. Diabetic patients who need to take insulin (more on that later) must inject it into the blood and not take it orally. The fact that it is a hormone means that it has a messenger function. It gives various cells in the body certain commands.

Blood Sugar

When we eat (digestible) carbohydrates, they raise the amount of glucose in the blood. We also say “the blood sugar level rises.” The pancreas responds by instructing the cells in the islets of Langerhans to produce insulin.

This ensures that besides glucose, insulin also enters the blood. Insulin then tells the various cells in the body how to use certain substances to produce or store energy. These cells have different receptors. A cell with its receptors can be seen as different doors with different keyholes. The insulin receptor responds only when there is enough insulin present and will only accept the message with instructions then.

The Influence of Insulin on “Blood Sugar,” Muscle Growth, and Increase in Body Fat

Insulin mainly ensures that the amount of glucose in the blood is not too high or too low. In case of a large increase, such as when eating a meal with a lot of sugars, insulin reduces the glucose in the blood. When the amount present is very low due to not having eaten sugars for a long time, insulin ensures that the body produces the necessary glucose itself.

Insulin regulates the blood sugar level by issuing various instructions to various cells. For example, when there is too much glucose in the blood, the following instructions are given:

Liver and Muscles: Take up more glucose

Glucose itself cannot be stored as an energy source but must be converted into glycogen. This happens in the liver and muscles. Insulin instructs the liver and muscles to take up more glucose. So when a lot of glucose enters the blood, insulin ensures that part of it is stored as a reserve and thus disappears from the blood.

Increase “Glycogenesis”

In the muscles, glucose must be converted into glycogen to be stored and used. This conversion into glycogen is called glycogenesis. Insulin ensures that more glucose is converted into glycogen, reducing the amount of glucose in the blood. The storage capacity for glycogen is limited. It is stored in the liver (about 100 grams), but most of it in the muscles (5,11). The more trained you are, the greater the storage capacity of the muscles (because the larger the muscles, the greater the storage capacity), although there is a maximum limit to this.

Various studies on this maximum capacity come with various results ranging from 500 grams to 1.1 kilos, with the differences caused, among other things, by the fitness of the test subjects (5-11). In practice, the storage of glycogen is sufficient to provide only 30 to 40 minutes of truly intensive exercise (12). Suppose you were training heavily for muscle mass without stopping, with minimal rest. Your glycogen stores would be empty within 40 minutes, and your body would stop storing glucose/glycogen and producing muscle proteins and start breaking down fats and muscle proteins to provide enough glucose.

Lower Gluconeogenesis

With the instruction to convert more glucose into glycogen, follows the step to conversely convert less glycogen into glucose. Conversion of glycogen into glucose occurs when there is insufficient glucose in the blood. Stored energy in the liver and muscles can thus be used for essential functions such as the brain and the cardiovascular system.

Glycogenesis is the creation of new glucose (from glycogen, among others) while glycogenolysis means the breakdown of glycogen into glucose. Glycogenolysis and glycogenesis both have the opposite effect of gluconeogenesis. Just to keep it simple.

Increase Protein Synthesis in the Muscles (Muscle Growth!)

Protein synthesis is the creation of protein from various amino acids. This creation of new protein in the muscles leads to muscle growth. Eating enough carbohydrates plays a role in signaling for muscle growth.

Eating enough protein is important because the consumed protein is broken down into amino acids needed as building blocks to later be rebuilt into protein in the muscles. When these are not present, the instruction to increase protein synthesis yields little result.

Increase Synthesis of Fatty Acids, “Lipogenesis” (Increase in Fat!)

This is the step that causes you to gain weight from eating too many carbohydrates. With an excess of glucose, insulin instructs the body to produce more fatty acids from glucose to store the excess energy when the glycogen supply is saturated (5, 13). This is (especially historically) necessary for survival. Glycogen can only be stored for a few hours (or, as mentioned above, only 30-40 minutes during intensive exercise).

In theory, fat can be stored for years. In practice, this results in people weighing over 200 kilograms. For illustration: The heaviest bodybuilder who stood dry on stage (Ronny Coleman) weighed almost 136 kilograms. The heaviest person ever according to Guinness weighed 550 kilograms! The average person has an energy supply consisting of fatty acids that is 200 times greater than that of glycogen. The choice of fuel depends on the intensity level. When you exert yourself to the point where you are utilizing more than 70% of your maximum oxygen intake (VO2max), your body switches to glycogen (11).

From Carbohydrates to Fat?

The image next shows the results of a study from 1988 on the processing of ingested carbohydrates (5). In this study, they first emptied the glycogen stores of their test subjects by eating relatively high-fat and low-carbohydrate diets for several days and following a training program. They then looked at how much carbohydrates were ingested (carbohydrate intake), how much of it was stored as glycogen (glycogen storage), how much of the stored glycogen was used (carbohydrate oxidation), and what portion of the stored glycogen was converted into fatty acids (de novo lipogenesis).

Main Tank and Reserve Tank

The storage in the muscles can be seen as your main tank and the liver as a reserve tank. When the muscles are “empty,” glycogen in the liver (liver glycogen) can be converted back into glucose to be transported in the blood. Upon reaching the muscles, it is converted back into glycogen. This does not work the other way around. Once in the muscles (muscle glycogen), glycogen cannot be converted back into glucose.

The enzyme glycogen-6-phosphatase that is responsible for the conversion of glucose to glycogen is not present in the muscles. The main tank and reserve tank thus provide the same type of energy. When the reserve tank is also empty, the body has the option to burn fats for energy. These provide more energy per gram (making them more effective for long-term storage), but can release this energy less quickly. Running a sprint or bench pressing heavily becomes difficult, but at least you have the energy to cycle home after the workout.

How Much Carbohydrates to Eat?

Over the approximately 2.5 million years in which many of the characteristics of modern humans (Homo sapiens) evolved in their predecessors, people were much more dependent on protein and fats. Because agriculture was not yet practiced, but people relied on hunting and gathering, relatively more meat and nuts, etc., were eaten (14-16). Also, for most of the 150 to 200 thousand years of modern human existence, hunting and gathering was the way people obtained food. This resulted in relatively more proteins and fats.

Only in the last 7,000 to 10,000 years has agriculture been practiced and carbohydrates became a larger source of energy. Nowadays, the advice usually is to get 50-55% of the total required energy from carbohydrates, 30-35% from fat, and 10-15% from protein. Although the ratio of fats and proteins is often discussed, and bodybuilders and strength athletes would get more protein and less fat, you see that carbohydrates provide at least half of the total required energy for most people (see calculator!). This can differ from region to region, but also from time to time.

Too Many Carbohydrates Nowadays?

Today, we get half or more of all required energy from carbohydrates. As mentioned, these can provide energy for only a few hours, or less during intensive exercise. Because carbohydrates are easily available (you buy bread at the bakery and don’t have to spear a mammoth first), this is not a problem. In prehistory, a good fat reserve was more valuable because it was always uncertain when you would see your next meal hanging in a tree or quickly run away because you forgot to “walk under the wind” and were smelled by your prey.

You can easily calculate how many calories you need and thus the number of carbohydrates (and proteins and fats) with my nutrition calculator.

Keep in mind the differences between fast and slow carbohydrates. If all your carbohydrates are fast sugars, chances are you’ll unintentionally create unwanted fat mass. Use fast carbohydrates only when they add value, such as directly before, during, and/or after training when your blood sugar level is lowered or has been lowered by your efforts during training (see also further).

Diabetes in Brief

The above mainly describes what should happen when everything goes well. In the case of diabetes, however, too little insulin is produced or insulin does not react to increases in glucose as it should. There are plenty of websites that provide detailed explanations of diabetes. Here, I will only briefly describe the characteristics of the two most common types and then go on to discuss their influence on strength training, muscle growth, and fat loss.

Type I Diabetes

• Occurs mainly in young people and was therefore also called “juvenile diabetes”.
• No insulin is produced at all.
• The “islets of Langerhans,” the cells that produce insulin, are destroyed by the body’s own immune system or an infection.
• Due to the lack of insulin, people with type I diabetes must inject insulin a few times a day (or wear an insulin pump).
• About 10% of all diabetics have type I.

Type II Diabetes

• Insulin is produced, but insufficiently.
• In addition, the body does not respond adequately to insulin (insulin resistance).
• Previously called “adult-onset diabetes,” but is increasingly occurring in young people.
• Overweight and lack of exercise, but also older age and genetic predisposition, increase the risk of type II diabetes.
• For treatment, dietary and exercise advice is often given. In some cases, insulin injections may also be necessary.
• About 90% of all diabetics have type II.

Diabetes, Strength Training, and Muscle Growth

Diabetes and strength training will be discussed here in two ways:

1. The effect of strength training and nutrition for muscle mass on diabetes.
2. The effect of diabetes on strength training, muscle growth, and fat loss.

In other words: Does strength training have a positive or negative effect on the different forms of diabetes? And vice versa: What effect does diabetes have on your results when you want to gain muscle mass or lose fat?

“Strength Training Lowers the Risk of Diabetes”

Regarding the first question, we can state that strength training has positive results for people with diabetes, particularly type II, the majority.

Various studies have shown this. A study published last year used data from a large-scale follow-up study in which over 32,000 men were followed for 18 years to provide information for various research purposes (17). During this time, 2,278 new cases of type II diabetes occurred. The researchers compared the amount of strength training the men had done and observed a negative correlation between strength training and the risk of type II diabetes. That is to say: The more strength training was done, the lower the risk of type II diabetes.

From two independent measurements, it was found that at least 150 minutes of strength training per week reduced the risk of type II diabetes by 34% and 52%, respectively. The combination of cardio and strength training (at least 150 minutes per week) was found to reduce the risk of type II diabetes by as much as 59%. The researchers do note that further research is needed to confirm their results and determine if these results also apply to women.

CONCLUSIONS Weight training was associated with a significantly lower risk of T2DM, independent of aerobic exercise. Combined weight training and aerobic exercise conferred a greater benefit.

A. Grøntved, Harvard School of Public Health

“Strength Training as Treatment for Diabetes (Type II)”

There are several reasons why strength training has a positive effect on reducing the risk of diabetes. One important reason is the increase in muscle mass. As mentioned, the risk of type II diabetes increases with age. This is partly explained by the decrease in muscle mass (as well as lack of exercise and increase in fat) (18-23). The muscles are, as mentioned, the largest storage place for glucose in the form of glycogen (19). A decrease in this muscle mass has been shown to increase the risk of insulin resistance and decrease glucose uptake. Conversely, good glycogen storage through training reduces the risk of type II diabetes (11).

The reduction of skeletal muscle glycogen after exercise allows a healthy storage of carbohydrates after meals and prevents development of type 2 diabetes.

J. Jensen, Norwegian School of Sport Sciences

Because the muscles become depleted more often (glycogen stores empty) through strength training, the body may also learn to process glucose more effectively (18). It has been found that strength training increases insulin sensitivity and improves glucose tolerance by increasing receptors responsible for glucose uptake in muscles and adipose tissue (“glut4 receptors”) (24-26). Many of the beneficial effects of strength training on the risk of diabetes are therefore mainly attributed to the increase in lean body mass that strength training can lead to.

“Bring on the Heavy Weights!”

The association between overweight and diabetes has been demonstrated in many studies. Therefore, many treatment methods for people with diabetes are aimed at weight management. This is partly because the combination of diabetes and overweight increases the risk of cardiovascular disease (27).

Researchers from the School of Exercise and Sport Science (University of Sydney) in Australia looked at weight training as an alternative treatment for elderly people with type II diabetes in a study called: “Battling Insulin Resistance in Elderly Obese People With Type 2 Diabetes. Bring on the heavy weights” (18). Besides proper nutrition, cardio is usually recommended for weight management. However, cardio is not always possible for older people with overweight and other

complaints. Strength training is a safer alternative for them (18).

Including PRT* in their treatment regimen, if successful, should improve physiological and psychological function, change body composition, and improve glucose homeostasis, resulting in improved quality of life.

*Progressive Resistance Training

K. Willey, School of Exercise and Sport Science, the University of Sydney

Researchers at Syracuse University in the U.S. came to the same conclusion (28):

Resistance exercise offers an alternative to aerobic exercise for improving glucose control in diabetic patients. To realize optimal glucose control benefits, individuals must follow a regular schedule that includes daily exercise.

L.M. Fennichia, Syracuse University, N.Y.

The Effect of Diabetes on Strength Training

So, strength training has a positive effect on how your body handles glucose and insulin. What about the reverse? What if you have diabetes and want to do intensive strength training because you want to do bodybuilding? Should you take into account, for example, your blood sugar levels because they are heavily depleted by training and therefore train less intensively? And what about nutrition?

Ironically, the diet of a bodybuilder seems more like that of a diabetic than that of the average person. A diabetic tries to avoid high peak levels of sugar in the blood because there is too little or no insulin to process it in time (or the body does not respond sufficiently to insulin), leading to a hyper (too high blood sugar level). On the other hand, a diabetic also pays attention to not letting blood sugar levels drop too low because the lack of (sensitivity to) insulin does not promptly cause the body to produce glucose.

Distributing Carbohydrates

A bodybuilder essentially does the same thing. By evenly distributing the total carbohydrate needs over many meals, a bodybuilder ensures that:

• There is always sufficient energy available, keeping the body in an “anabolic state.” Anabolic means that the body builds new tissue from existing building blocks such as muscle mass, but also fat. In the absence of carbohydrates and thus energy, the body switches to a catabolic state in which tissue in the body is broken down to provide energy.
• Not too much sugar enters the body at once, preventing the body from creating extra fat tissue (lipogenesis as discussed above).

Especially slow carbohydrates

For both diabetics and bodybuilders, quick, simple, refined sugars should normally be avoided as much as possible, and slow, complex carbohydrates should be chosen instead. Complex carbohydrates provide a more gradual release of sugars into the blood and therefore do not lead to a rapid increase in blood sugar levels like simple, quick carbohydrates. The exception to this also applies to both. Specifically, quick, simple carbohydrates should be consumed when the blood sugar level is very low, for example, because most of the fuel has been consumed due to heavy exertion.

When to use fast sugars?

Many bodybuilders choose to ingest a lot of fast sugars at once (such as dextrose or maltodextrin) so that glycogen stores can be filled immediately, and the insulin produced can instruct the muscles to increase protein synthesis (muscle growth) (although some bodybuilders wait half an hour to avoid inhibiting the production of growth hormone. More on this in a separate article).

After training, quick carbohydrates may also be necessary for diabetics to replenish depleted glycogen stores regarding muscle growth, but especially to quickly raise blood sugar levels for more important functions such as the brain. In “normal bodybuilders,” the body still has the ability to sacrifice muscle mass for brain functions. Not so for diabetics.

Hyper

Bodybuilders may also choose to consume fast carbohydrates before training to provide energy during the training. As a diabetic, you should be careful if your blood sugar level is already high at that time. It may take a while for it to start to decrease due to your efforts. You have read above what the consequences of a hyper, when your blood level is too high, can be. Things like fatigue, nausea, and vomiting are the last things you want when you walk into the gym. So you’d better choose to eat complex carbohydrates a little earlier rather than throwing in fast carbohydrates just before training.

Important for the training diabetic!

Measure your blood sugar level before, after, and possibly during training. Someone who does not have diabetes can afford to train too long while glycogen stores are empty and blood sugar levels are low. The worst that can happen then is that muscle mass is broken down to provide you with energy to continue training to grow your muscles (mopping with the tap open). This must be carefully monitored for a diabetic.

In addition, it is even more important for a diabetic to be consistent with the meals before and after training and to adjust them to each other. This way, you learn how many carbohydrates you need and when, and what influence a certain intensity of training has on your blood sugar level.

Go see the doctor!

Many articles on training and exercise in general, as well as the information on almost every fitness device, will advise you to consult your doctor before starting to train. Since this site often writes articles for people who already have more experience with training, you will not have come across such a warning here yet. However, if you have diabetes, it is advisable to consult your doctor first. He or she knows your specific situation and can assess the pros and cons and any limitations (if any) well.

Diabetes and protein supplements

“(Extra) Protein is good for diabetics to replace carbohydrates that fluctuate blood sugar”

“(Extra) Protein is bad for diabetics because it overloads the kidneys too much

Nice isn’t it when everyone agrees with each other.

The maximum amount of protein that you can take daily without complaints such as the effect on the kidneys on the one hand and the added value in terms of muscle growth on the other hand, is the subject of the next article that I will write. For and by diabetics, concern about an excess of protein is often expressed because this would burden their (they say) already heavily loaded kidneys even further.

Diabetes and the kidneys

Damage to the kidneys due to diabetes is called diabetic nephropathy (nephron = kidney, pathy = disease). Patients with diabetes who have been injecting insulin from a young age are at the highest risk. But even in patients who are diagnosed with diabetes at a later age, nephropathy can occur. With diabetic nephropathy, the function of the kidneys gradually deteriorates over a period of years. Ultimately, kidney function can deteriorate to such an extent that
chronic kidney failure (insufficient kidney function) occurs.

Source: “Kidneys, kidney diseases and treatment: Kidneys and Diabetes”. Dutch Kidney Foundation

Proteins and the kidneys

Protein is often said to burden the kidneys too much if intake is too high. The question then, of course, is: “What is too much?”. Anticipating an article yet to appear on protein, I can already state here that the amount normally used by bodybuilders should not pose a risk, even for diabetics. Most bodybuilders use between 2 and 2.5 (sometimes 3) grams of protein per kilogram of body weight daily, but excesses of 400 grams per day occur (29-31).

Various studies show that 2 to 2.5 grams of protein per kilogram of body weight should be able to be ingested without risks (32) also by most diabetics (33). In fact, researchers at the Harvard Medical School recommend keeping protein intake below 1 gram per kilogram of body weight only when there are specific kidney problems as discussed above. In cases of kidney problems, they recommend getting 0.8 to 1 gram of protein per kilogram of body weight per day (33).

Be careful! Diabetes does indeed pose a higher risk of kidney disease and kidney failure. It is therefore important for a diabetic to have their kidney functions checked regularly so that you know in time when this needs to be taken into account.

Insulin as doping

You have read above about various beneficial

effects of insulin on muscle growth. It is therefore not entirely surprising that some athletes, competitive bodybuilders in particular, misuse insulin to achieve better performance. Especially the anti-catabolic effect, the fact that it inhibits or even stops muscle breakdown, makes it attractive for some bodybuilders. However, the fact that the muscles fill up with glycogen and thus have fuel for longer, makes them “attractive” for a very broad group. For example, cyclist Michael Rasmussen confessed earlier this year that he used insulin.

The same effects are attributed to insulin as to certain anabolic steroids. Most anabolic steroids work “much better” than insulin when it comes to added muscle mass. However, insulin has a half-life of only 4 to 6 minutes (34,35). It leaves the blood entirely within a week. Until 2007, laboratory technicians could not even distinguish between chemically manufactured insulin and endogenous insulin. This made detection much more difficult or even impossible, making it seen as an interesting alternative for certain competitive athletes.

Insulin dangerous as doping

However, insulin is much more dangerous than anabolic androgenic steroids (AAS). Even the most hardcore anabolic gurus who try everything often advise against using insulin. AAS generally only pose the more threatening situations in the longer term. However, a single overdose of insulin can already lead to a fatal coma. The blood is then so “robbed” by the muscles that fill up with glycogen that there is insufficient left for the brain. Due to personal differences, it is very difficult to determine how much insulin someone could safely use. On forums, you sometimes hear advice on dosages that might work for the person themselves, but could immediately lead to a severe hypo in someone else.

Insulin is therefore mainly abused by athletes who are willing to take these risks because the chances of getting caught are smaller.

If you train as a “hobbybuilder” just to look good and insist on using doping to achieve more or faster results, there are many “better mistakes” you can make than insulin.

Types of carbohydrates

Carbohydrates are sugars, or saccharides. Chemically, carbohydrates are molecules consisting of compounds of carbon (C), hydrogen (H), and oxygen atoms (O). Of course, this applies to many molecules. However, for most carbohydrates, there is a specific ratio between the carbon and hydrogen atoms, namely 1:2.

“Hydrate of carbon”

The word “carbohydrate” comes from “carbon” and “hydrate.” Originally, what we now consider as “carbohydrates” were seen as “hydrate of carbon”. A hydrate is a molecule to which a water molecule has been added. The most important carbohydrate, glucose, was thought to be a hydrate with the structure C₆(H₂O)_6. That is, six carbon atoms coupled with six water molecules. For this reason, it was wrongly called “carbohydrate” (English: carbohydrate, hydrate of carbon). However, the correct structure turned out to be C₆H12O₆ (figure right), the same atoms but formed differently.

Before you break your head trying to understand this: It is only important here that the word carbohydrate is actually incorrect. Often the ratio of 1:2 applies to the number of carbon atoms compared to the number of hydrogen atoms as seen in the formula of glucose (twice as many hydrogen atoms as carbon atoms), but this does not apply to all types of carbohydrates.

The function of carbohydrates in nature

In the following sections, the role of carbohydrates in nutrition will be extensively discussed. For now, I will limit myself to naming the supply of energy as the most important function of carbohydrates in nature. Plants form carbohydrates as a source of energy in the form of starch. They do this by converting carbon dioxide into glucose with the help of photosynthesis (light energy). Humans and animals obtain carbohydrates from food, but also form them themselves in the body from more complex carbon compounds. Thus, other types of carbohydrates can be converted into glucose in the body, but fats and amino acids can also be used for this purpose.

Glucose

Specifically, glucose is important for us because it is the only carbohydrate that can be absorbed into our bloodstream for transport to provide the various parts of the body with the necessary energy. In the following sections, glucose, glycogen (the stored form of glucose in the body), and the speed at which glucose is absorbed into the blood (glycemic index and load) will be discussed separately. The latter is important for things like available energy for activity, muscle mass synthesis and breakdown, and body fat synthesis and breakdown.

Different Types of Carbohydrates

Carbohydrates can be classified in various ways. The most relevant in this context are:

• Consisting of one or more saccharides (simple or complex)
• The number of saccharides forming the carbohydrate
• Simple & complex
• Digestible and non-digestible carbohydrates (fibers)
• Number of carbon atoms
• Isomers: alpha and beta (α & β), L and D

Carbohydrates from One or More Saccharides (Simple and Complex)

As mentioned, there are different types of carbohydrates, or saccharides. Some saccharides together form another type of carbohydrate. When a carbohydrate consists of one type of saccharide, it is called a simple carbohydrate. If the carbohydrate consists of multiple saccharides, it is called a complex carbohydrate.

Examples of simple carbohydrates:

• Glucose
• Fructose
• Galactose

Examples of complex carbohydrates:

• Lactose. The carbohydrates in milk formed by glucose and galactose
• Sucrose. What we know as the (cane) sugar you buy in the store, is formed by glucose and fructose

The Number of (Chains of) Saccharides Forming the Carbohydrate

So there are carbohydrates that consist of one or more saccharides. Another classification is based on the number of saccharides forming the carbohydrate, which also distinguishes between the different complex carbohydrates.

• Monosaccharide: Glucose, as mentioned, is a simple carbohydrate and consists of one saccharide. According to this classification, this is called a monosaccharide. A simple carbohydrate is always a monosaccharide.
• Disaccharide: Consists of two (chains of) saccharides. The examples above of the complex carbohydrates sucrose and lactose are both disaccharides.
• Oligosaccharides: These consist of 3 to nine chains of saccharides. An example of this is kestose (found in onions), which is formed from 2 fructose molecules and 1 glucose molecule.
• Polysaccharides: Formed by more than nine chains of saccharides. Starch, for example, is formed from the two polysaccharides amylose and amylopectin, both of which consist of hundreds to thousands of glucose chains.

Digestible and Non-digestible Carbohydrates

A completely different subdivision is the way carbohydrates are processed in digestion (or not processed) into glucose. Most carbohydrates are digested in the small intestine before they reach the large intestine. However, some cannot be digested in the small intestine. These “non-digestible carbohydrates” (enlignins) are called dietary fibers.

However, the term “non-digestible” only refers to processing in the small intestine. Once in the large intestine, some of these dietary fibers can still be digested by bacteria in the large intestine (“intestinal flora”) in a process called fermentation. This still provides energy. So only a portion of the “non-digestible carbohydrates” cannot be digested.

Number of Carbon Atoms

Then two more, possibly less interesting, ways to classify carbohydrates. I mention them only so that you know the terms and understand to what extent they are (not) relevant when researching the role of carbohydrates in achieving your goals.

The first is based on the number of carbon atoms:

• Triose: three carbon atoms
• Tetrose: four carbon atoms
• Pentose: five carbon atoms
• Hexose: Glucose, C₆H₁₂O₆, has six carbon atoms and is therefore called a hexose (hexa = 6)
• etc

Isomers Alpha and Beta (α & β), L and D

The last subdivisions will hardly be addressed in the following articles on carbohydrates and I will therefore describe them very briefly. This concerns the different isomers. Isomers are molecules with the same atoms but in a different arrangement. I will briefly explain this with glucose as an example.

Alpha and beta: α-glucose (left) and β-glucose (right) are so-called anomers of each other. They are actually the same carbohydrate with one small difference. The OH group at the first position (C¹) points downwards in alpha, while in β-glucose it is on the other side.

In addition, there is the difference between D-Glucose and L-Glucose. D-Glucose is the form most commonly found in nature (grape sugar). The difference between L- and D-glucose is the hydroxymethyl group at the fifth position (C⁵) (not shown).

There are therefore 4 possible isomers of glucose:

• α-D-glucose
• β-D-glucose
• α-L-glucose
• β-L-glucose

The two different carbohydrates maltose and lactose are also isomers of each other. They both have the same molecular formula, C₁₂H₂₂O₁₁, and thus have the same atoms. However, these are arranged in a different structure (structural formula).</p >

Summary

• There are various types of carbohydrates/sugars/saccharides. You can classify them based on the number of sugar chains connected to each other (mono-, di-, oligo-, and polysaccharides).
• Other ways to classify carbohydrates include: Slow vs. fast, simple vs. complex, and simple vs. complex.
• A final distinction is digestible and non-digestible (sugars and dietary fibers respectively). Sugars form glucose via the small intestine. Fibers provide energy through fermentation in the large intestine.
• Of the various sugars, only glucose can pass through the intestinal wall and be absorbed into the bloodstream. Other sugars are therefore converted into glucose in the body. Glucose is stored in the form of glycogen.
• The glycemic index provides insight into the speed at which a certain type of carbohydrate can raise the amount of glucose in the blood.
• Glycemic load does the same as the glycemic index, but also takes into account the amount of carbohydrates in a certain type of food.
• Insulin regulates the amount of glucose in the blood.
• More insulin in the blood causes: – More glucose to be converted into glycogen stored in the liver and muscles. – More glucose to be converted into fat that can be stored. – Protein to be formed from amino acids, leading to muscle growth.
• Carbohydrates can only be stored as glucose/glycogen to a limited extent. At full exertion, glycogen provides energy for a maximum of 30 to 40 minutes. Fat provides energy much more slowly but can be stored in much larger quantities.
• Normally, the advice is to get 50-55 percent of the required amount of calories from carbohydrates. Historically, people ate much fewer carbohydrates. It is important to eat slow and fast carbohydrates at the right times.
• In the case of diabetes, too little insulin is produced or insulin does not respond to an increase in glucose as it should.
• Strength training reduces the risk of diabetes.
• Strength training improves the way glucose can be processed in diabetics.
• The diet of a bodybuilder and that of a diabetic need not differ much. Both distribute sugar intake throughout the day to prevent high peak values and deficiencies.
• The increased protein intake by bodybuilders and strength athletes does not pose a risk to the kidneys of diabetics unless there are already kidney problems.
• Insulin is used by some athletes as doping because it is difficult to detect in doping controls. However, the benefits are smaller than with anabolic use while the dangers are greater.

References

1. F. Smet, P. Lambers. Biochemie. WKB Diegem, 6th edition
2. Jenkins DJ, Wolever TM, Taylor RH, et al. (March 1981). “Glycemic index of foods: a physiological basis for carbohydrate exchange”. Am. J. Clin. Nutr. 34 (3): 362–6. PMID 6259925.
3. “GI Database”. Web.archive.org. Retrieved 2012-08-01.
4. Freeman, Janine (September 2005). “The Glycemic Index debate: Does the type of carbohydrate really matter?”. Diabetes Forecast. Archived from the original on February 14, 2007.
5. Acheson K. J., Schutz Y., Bessard T., Anantharaman K., Flatt J. P., Jequier E. (1988). Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man. Am. J. Clin. Nutr. 48, 240–247. [PubMed]
6. Bergstrom J, Hermansen L, Hultman E, Saltin B. Diet, muscle gly- cogen and physical performance. Acts Physiol Scand l967;7 1: 140-50.
7. Hultman E, Nilsson LH. Liver glycogen in man. Effect of different diets and muscularexercise. Adv Exp Med Biol 1971; 11:143-51. 3. Nilsson LH. Liver glycogen content in man in the postabsorptive
8. Hedman R. The available glycogen in man and the connection between rate ofoxygen intake and carbohydrate usage. Acta Physiol Scand l957;40:305-2l. 22.
9. Bjorntorp P, SjostromL. Carbohydrate storage in man: speculations and some quantitative considerations. Metabolism l978;27(suppl 2): 1853-65.
10. Olsson KE, Saltin B. Variations in total body water with muscle glycogen changes in man. Acts Physiol Scand l970;80:1 1-8.
11. Jørgen Jensen, Per Inge Rustad, Anders Jensen Kolnes and Yu-Chiang Lai. The Role of Skeletal Muscle Glycogen Breakdown for Regulation of Insulin Sensitivity by Exercise. Front Physiol. 2011; 2: 112. doi: 10.3389/fphys.2011.00112
    PMCID: PMC3248697
12. van Loon LJC. The effects of exercise and nutrition on muscle fuel selection. Maastricht:
    Universitaire Pers Maastricht, 2001.
13. Jensen J., Lai Y. C. (2009). Regulation of muscle glycogen synthase phosphorylation and kinetic properties by insulin, exercise, adrenaline and role in insulin resistance. Arch. Physiol. Biochem. 115, 13–21. doi: 10.1080/13813450902778171.
14. Eaton, S.B., S.B.(3rd) Eaton, and M.J. Konner. Paleolithic nutrition revisited: A
    twelve year retrospective on its nature and implications. Eur. J. Clin. Nutr. 1:207-216,
    1997. Issues of Dietary Protein Intake in Humans 147
15. Cordain, L., J. Brand-Miller, S. Eaton, N. Mann, H.A. Holt, and J.D. Speth. World wide hunter gatherer (Plant:Animal) subsistence ratios: relevance for present day macronutrient recommendations. Am. J. Clin. Nutr. 71:682-692, 2000.
16. Mann, N. Dietary lean red meat and human evolution. Eur. J. Nutr. 39:71-79, 2000.
17. Grøntved A, Rimm EB, Willett WC, Andersen LB, Hu FB. A prospective study of weight training and risk of type 2 diabetes mellitus in men. Arch Intern Med. 2012 Sep 24;172(17):1306-12.
18. Willey KA, Singh MA. Battling insulin resistance in elderly obese people with type 2 diabetes: bring on the heavy weights .Diabetes Care. 2003 May;26(5):1580-8.
19. De Fronzo RA, Jacot E, Jequier E, Maeder E, Wahren J, Felber JP: The effect of insulin on the disposal of intravenous glucose: results from indirect calorimetry and hepatic and femoral venous catheterization. Diabetes 30:1000–1007, 1981
20. Vaag A, Henriksen JE, Beck-Neilsen H: Decreased insulin activation of glycogen synthase in skeletal muscles in young nonobese Caucasian first-degree relatives of patients with non-insulin-dependent diabetes mellitus. J Clin Invest 89:782–788, 1992
21. Nyholm B, Qu Z, Kaal A, Pedersen SB, Gravholt CH, Andersen JL, Saltin B, Schmitz O: Evidence of an increased number of type 2b muscle fibers in insulin-resistant first-degree relatives of patients with NIDDM. Diabetes 46:1822–1828, 1997
22. Albright A, Franz M, Hornsby G, Kriska A, Marrero D, Ullrich I, Verity LS: American College of Sports Medicine position stand: exercise and type 2 diabetes. Med Sci Sports Exerc 32:1345–1360, 2000 Medline
23. Nina Hovanec, Anuradha Sawant, Tom J. Overend, Robert J. Petrella, Anthony A. Vandervoort. Resistance Training and Older Adults with Type 2 Diabetes Mellitus: Strength of the Evidence. J Aging Res. 2012; 2012: 284635. Published online 2012 September 4.
24. Miller J, Pratley RE, Goldberg AP, Gordon P, Rubin M, Treuth MS, Ryan AS, Hurley BF: Strength training increases insulin action in healthy 50- to 65-yr-old men. J Appl Physiol 77:1122–1127, 1994
25. Fluckey JD, Hickey MS, Brambrink JK, Hart KK, Alexander K, Craig BW: Effects of resistance exercise on glucose tolerance in normal and glucose-intolerant subjects. J Appl Physiol 77:1087–1092, 1994
26. Tesch P, Colliander E, Kaiser P: Muscle metabolism during intense heavy-resistance exercise. Eur J Appl Physiol Occup Physiol 55:362–366, 1986 CrossRefMedline
27. Tresierras MA, Balady GJ. Resistance training in the treatment of diabetes and obesity: mechanisms and outcomes. J Cardiopulm Rehabil Prev. 2009 Mar-Apr;29(2):67-75.
28. Fenicchia LM, Kanaley JA, Azevedo JL Jr, Miller CS, Weinstock RS, Carhart RL, Ploutz-Snyder LL. Influence of resistance exercise training on glucose control in women with type 2 diabetes. Metabolism. 2004 Mar;53(3):284-9.
29. Lemon, P.W. Beyond the zone: protein needs of active individuals. J. Am. Coll. Nutr. 19:513S-521S, 2000.
30. Forslund, A.H., A.E. El-Khoury, R.M. Olsson, A.M. Sjodin, L. Hambraeus, and V.R. Young. Effect of protein intake and physical activity on 24-h pattern and rate of macronutrient utilization. Am. J. Physiol. 276:E964-E976, 1999.
31. Poortmans, J.R., and O. Dellalieux. Do regular high protein diets have potential health risks on kidney functions in athletes? Int. J. Sport. Nutr. Exerc. Metab.10: 39-50, 2000.
32. Bilsborough S, Mann N. A review of issues of dietary protein intake in humans. Int J Sport Nutr Exerc Metab. 2006 Apr;16(2):129-52.
33. Hamdy O, Horton ES. Protein content in diabetes nutrition plan. Curr Diab Rep. 2011 Apr;11(2):111-9.
34. Duckworth WC, Bennett RG, Hamel FG (October 1998). “Insulin degradation: progress and potential”. Endocr. Rev. 19 (5): 608–24.
35. Palmer BF, Henrich WL. “Carbohydrate and insulin metabolism in chronic kidney disease”. UpToDate, Inc.
36. Chandalia, M., Garg, A., Lutjohann, D., von Bergmann, K., et al., Beneficial effects of high dietary fiber intake in patients with type 2 diabetes mellitus. New Engl. J. Med. 2000, 342, 1392 – 1398.
37. Jenkins, D. J. A., Geoff, D. V., Leeds, A. R., Wolever, T. M. S., et al., Unabsorbable carbohydrates and diabetes: Decreased postprandial hyperglycaemia. Lancet 1976,I, 172 – 174.
38. Jenkins, D. J. A., Leeds, R., Gassul, M. A., Cochet, R., Alberti, K. G. M. M., Decreased post prandial insulin and glucose concentration by guar and pectin. Ann. Int. Med. 1977, 86, 20 – 23.
39. Jenkins, D. J. A., Goff, D. V., Leeds, R., Gassul, M. A., et al., Dietary fibres, fibre analogues, and glucose tolerance: importance of viscosity. Brit. Med. J. 1978,I, 1392 – 1394. [20] Jenkins, D. J. A., Wolever, T. M. S., Taylor, R. H., Barker, H. M., Fielden, H., Exceptionally low blood glucose response to dried beans: comparison with other carbohydrate foods. Brit. Med. J. 1980, 281, 578 – 570.
40. Jenkins, D. J. A., Wolever, T. M. S., Kalmusky, J., Giudici, S., et al., Low glycaemic index carbohydrate foods in the management of hyperlipidaemia. Am. J. Clin. Nutr. 1985, 42, 604 – 617.