A Discussion on Carbohydrate Continues…

Image Source: https://www.fmtv.com/watch/carb-loaded

A Discussion on Carbohydrate Continues…

Carbohydrates

By: Jared Miller

 

Introduction

It was established in the previous article that there is an optimal range of carbohydrate consumption in the diet. For optimum function of the human body, one must adequately provide glucose for the red blood cells and brain cells. In addition, glucose is a usable source of energy for muscle cells, and the remainder of the cells in the human body. For a detailed overview of carbohydrate metabolism read the whole article, or begin at ‘Recommended Carbohydrate Intake’ for a quicker read.

 

A Brief Overview of Metabolism

Formally, metabolism is the sum of all chemical processes taking place in the body. Further, the basal metabolism is the baseline necessary to maintain bodily functions in warm-blooded animals at rest, such as while taking a nap. Basal metabolic rate is affected by many factors such as gender, body composition and age. There are catabolic (breaking down) processes that occur in the body, and there are anabolic (building up) processes that occur in the body. Therefore metabolism is all of those combined, which means that someone with a ‘fast’ or ‘high’ metabolism has a high rate of breaking down and building up processes taking place in their body, while a person with a ‘slow’ or ‘low’ metabolism has a lower rate of breaking down and building up processes taking place in their body which is affected by hormones primarily. Catabolism + Anabolism = Metabolism

 

Catabolism and Anabolism Exemplified

An individual eats a piece of bread. The bread made of starch will be catabolized into glucose during digestion. The glucose will be absorbed into the bloodstream and travel to the liver. The liver will perform metabolic processes that will allow for some of that glucose to continue its journey in the bloodstream to reach the rest of the body, where it can be utilized for energy by cells such as the muscle cells, which will store glucose as glycogen for when it is needed for activity. As well, some of the sugar will also be converted into glycogen in the liver, which is also an anabolic process. If the person eats too many carbohydrates for the needs of their body at that time, excess glucose will be used to synthesize triglycerides (fat) to be stored as fat in the adipose tissue, this is an anabolic process as well. Indeed, if that person then goes to the gym and runs intervals on the treadmill, their body will begin to catabolize the glycogen stored in their liver and muscles primarily, until their body begins to shift more toward breaking down (catabolizing) triglycerides for energy.

Overall, it is clear that there are a lot of processes taking place in the human body all at once, and this means that the human body is not a rigidly functioning entity, but is actually ‘fluid’ or ‘transient’ in nature. Considering this, it is possible to move onto the topic of Carbohydrate metabolism and how that affects other areas of the body.

 

Glycemic Load and the Internal Environment

Remember the concept of glycemic load? (If not, refer to this article) Well, glycemic load is a paramount concept in regards to carbohydrates in the diet. As mentioned earlier, the internal environment of the human body is in a constant state of flux, meaning at one time of day the processes occurring in the body can be different from the processes occurring at another time of day, and it does not take long to shift drastically. For instance, an individual could be utilizing primarily fat stores for energy production, and then consume a spoonful of sugar with a high glycemic load and within seconds, their body progressively begin to shutdown ‘fat burning’ processes, in favour of fat storage processes. Let’s have a more detailed examination of this concept using a case scenario, followed by an explanation.

 

Case Scenario

Bob is a male, 35 years old, and 180 lbs., 5’7’ and his body fat percentage is 19%. Bob spends two hours per week on his self directed resistance training and two hours per week on his self directed aerobic exercise per week, he has researched on the internet and interprets for himself that he exceeds the criteria to be considered an active male according to Health Canada (Health Canada, 2014). Bob has decided he needs to lose some weight, and so he has cut his calorie intake to approx. 2000 Calories per day, a reduction from his previous intake of approx. 2900 Calories.

For breakfast, Bob eats 3 eggs, two packets of oatmeal, and a tablespoon of brown sugar on top and glass of orange juice. This meal contains roughly 18grams (g) of fat, 20g of protein, and 100g of carbohydrates (5 g of fiber, 60 g of starch, 35g of sugar)

For lunch, Bob eats a chicken Caesar wrap containing approx. 10g of fat, 25g of protein and 35 g of carbs (2 g of fiber, 31 g of starch, 3 g of sugar).

For afternoon snack, Bob eats an apple containing approx. 25 g of carbs (4g of fiber, 2g starch, 19g of sugar)

For dinner, Bob eats two lean beef hamburgers on whole wheat buns with ketchup, mayo, tomato, iceberg lettuce, containing approx. 24 g of fat, 50g of protein, 65 g of carbs (4g of fiber, 49g of starch, 12 g of sugar)

For a late night snack Bob eats a piece of whole wheat toast with a tablespoon of peanut butter and a glass of milk containing approx.11g of fat, 15g protein, 34 g carbs (3g of fiber, 17 g of starch, 14g of sugar).

 

Total Nutrition Breakdown for Bob

Fat Protein Carbs total Fiber Starch Sugar
Grams (g)63g110g259g18g159g83g
Calories (kcal)564 kcal440 kcal968 kcal0 kcal636 kcal332kcal
Calories from source/Calories total564kcal/

1972 kcal

440kcal /

1972 kcal

960kcal/

1972kcal

Percent of Calorie Intake29%23%48%

 

Discussing Metabolic Patterns

Without discussing Calorie intake (requires an article of its own), let us take a look at what is happening inside Bob’s body. During sleep, Bob’s blood sugar has been maintained by slow release of glycogen from his liver. As the liver glycogen levels become increasingly lower over the course of the night, his body is beginning to mobilize his fat stores to provide energy to his cells. Glycerols from the triglycerides molecules in his fat are being converted into glucose to supplement the remaining liver glycogen, and fatty acids are also being utilized for energy by cells that can do so.

As the morning approaches, his liver glycogen is virtually non-existent. His body needs to further supplement the remaining liver glycogen and glycerol with another source of energy. Where does this supplemental supply of energy come from? It comes from small amounts of proteins, primarily sourced from muscle cells that travel to the liver to be converted into glucose (a process called gluconeogenesis, literally, ‘generating new sugar’), to be circulated in the blood stream.

At breakfast time, the orange juice, oatmeal and brown sugar will be digested in the Gastro-intestinal tract, will be processed in the liver and distributed in the blood stream. The protein from the egg white will be processed and distributed, and the fat from the egg yolk too. Clearly the liver is very important in the processing of nutrients, but let us introduce another influential organ known as the pancreas. The pancreas and the liver are highly involved in maintaining blood sugar and they work in concert.

The carbohydrates in Bob’s breakfast have entered the blood stream, and the pancreas will ‘taste’ the blood and release a hormone called insulin in relative proportion to the rise in blood sugar levels. Therefore, the major spike in blood sugar bolsters a major spike in insulin secretion, influenced by a food’s glycemic load. Insulin will travel in the blood stream and it will affect all cells that have receptors for insulin, such as the muscle cells and the fat cells. When insulin binds to these receptors, the cells will ‘open the gates’ and let glucose and other molecules such as amino acids, fats or other compounds into the cell.

One consequence of insulin binding to receptors on the cells is signaling the cells to slow down or cease the creation of ‘cellular machinery’ that are needed to utilize fat for energy, thereby slowing or halting the process of catabolizing fat, and in turn, promoting the storage fat. In the healthy human body, many processes are relatively proportionate; therefore, a 10g serving of carbohydrates would cause a tenfold increase in insulin levels when compared to a 1g serving of the same carbohydrate.

It is likely that much of the carbohydrates in his breakfast became glycogen in his liver, and some may have become glycogen in his muscles. However, since he shutdown a large proportion of his fat burning machinery, his body will reduce its dependence on burning fat for energy and he will be slowing down the process of losing fat weight. It is likely that the fat from the eggs will either add to his fat stores, or approximately ‘replace’ fat lost during the night.

This same cycle of processes will continue to varying degrees for the rest of the day, but ultimately, even in the midst of a Caloric deficit (i.e. taking in less energy than he is expending) he will preferentially be maintaining or even storing fat with every meal. What often happens with this type of diet is that the person loses weight, but it is not only fat that they lose, but also lean body mass. Recall the concept of basal metabolic rate and consider that a relatively high amount of Calories are required to maintain muscle. Therefore, after losing both fat and some muscle, his basal metabolic rate is now lower than it was before. This means he has just reset his body to a lower baseline level. This is a negative outcome as it is a major contributing factor to ‘yo-yo’ dieting, where the individual loses weight, eventually gains some back, loses some more weight (and more muscle), lowers their basal metabolic rate again, and the cycle continues unless there is some kind of clear, evidence-based intervention.

Review the article again and keep in mind that the body is never purely burning fat, nor purely utilizing carbs. It is however, constantly responding to its external and internal environment, by adapting its processes to maintain homeostasis or balance. In terms of gaining, losing or maintaining weight, it is the blood sugar levels that are the easiest part of the equation to consider, since a rise in blood sugar above normal levels is going to signal anabolic processes to take place (could be fat storage or muscle growth, depending on the person’s overall nutrition and activities), while lower range blood sugar levels will signal catabolic processes to take place (could be fat burning or muscle wasting depending on the person’s overall nutrition and activities). As well, it is impossible for anybody to explain the absolute truth about human biochemistry because it is so complex, nevertheless, it does accurately describe the principles behind the biochemistry, because the principles are relatively simple and predictable.

 

Recommended Carbohydrate Intake

My personal recommendation for overweight individuals trying to lose fat without professional supervision:

  • 0.5g – 1g of carbohydrates (excluding fiber) per pound of the target bodyweight per day.

Ex. A 160lb. woman who would need to lose 30lbs of fat to be optimally healthy would eat between 65g and 130g of carbohydrates per day, with a maximum of 15g coming from sugar and at least an additional 25g coming from fiber.

Preferably consuming no carbs until at least lunch, to not shut down fat burning processes during the morning. Eat a serving of meat, fish or eggs and ¼ cup of nuts for breakfast, and 500ml of water (coffee doesn’t count).

Preferably consuming majority of carbs post workout. The sooner the better because this is the time that carbs will be preferentially stored as muscle glycogen for your next workout.

In addition, consuming between 1g and 1.5 g of protein per pound of the target bodyweight to promote satiety and muscle maintenance or growth during a period of fat loss, to prevent lowering their basal metabolic rate.

Drinking at least 1.5- 2 L of water per day.

 

My personal recommendation for normo-weight individuals trying to maintain bodyweight:

  • 1g -1.5g of carbohydrates (excluding fiber) per pound of bodyweight per day.

Ex. A 150lb. lean male, would eat between 150g and 225g of carbohydrates per day, with a maximum of 25g coming from sugar and at least an additional 25g coming from fiber.

Preferably consuming no carbs until at least lunch, to not shut down fat burning processes during the morning. Eat a serving of meat, fish or eggs and ¼ cup of nuts for breakfast, and 500ml of water (coffee doesn’t count).

Preferably consuming majority of carbs post workout, the sooner the better because this is the time that carbs will be preferentially stored as muscle glycogen for your next workout.

In addition consuming 1g of protein per pound of bodyweight to maintain or encourage muscle mass.

Drinking at least 1.5- 2 L of water per day.

 

My personal recommendation for underweight individuals who need to gain body lean body mass:

  • 1.5g – 2g of carbohydrates per pound of the target bodyweight per day.

Ex. 95lb. female who would have to gain 20 pounds of body mass to be optimally healthy would eat between 175g and 230g of carbohydrates per day, with a maximum of 25g coming from sugar and at least an additional 25g of fiber.

Preferably consuming minimal carbs until at least lunch, to not shut down fat burning processes. Eat a serving of meat, fish or eggs and ¼ cup of nuts for breakfast, and 500ml of water (coffee doesn’t count).

Preferably consuming the majority of carbs post workout. The sooner the better because this is the time that carbs are preferentially stored as muscle glycogen for your next workout.

In addition, consuming between 1g and 1.5 g of protein per pound of the target bodyweight to promote lean growth of lean mass without gaining much fat (which may be a concern that caused these individuals to be underweight).

Drinking at least 1.5- 2 L of water per day.

 

Method of Calculating

Dosing coefficient in grams per pound X target bodyweight in pounds = Recommended Daily Intake

Ex. 1.5g/lb. X 100lbs = 150g.

 

Summary of General Recommendations

Overweight individuals who need to lose fat to be optimally healthy should be eating less carbs because this will allow their body to shift towards fat breakdown for energy. The extra protein will help stave off hunger, promote muscle growth or maintenance and if necessary, will provide the liver with materials to create glucose in the relative shortage of carbohydrates in the diet.

Normoweight individuals maintaining their weight can consume a moderate amount of carbs preferentially after workouts, since this will be less likely to contribute to fat storage. The regular protein consumption will help them maintain their muscle mass.

Underweight individuals who need to gain weight to be optimally healthy should still be consuming their relatively high amount of carbs post workout to help them build lean mass, while minimizing storage of fat. The extra protein in their diet will help to promote muscle growth.

In all populations there is always a need to consume lots of water and lots of vegetables.

In all populations there is always the freedom to adjust intake based on necessity, hence why there were ranges provided. Consume in the lower ranges when you expend less energy in your daily activities, and closer to the upper range when you expend more energy. Listen to your body.

 

Conclusion

Similarly to protein and fat, carbohydrates are a vital nutrient that should be consumed with consideration for the needs of the body. In this era of increasing knowledge about the human body it is possible to tailor nutritional needs to meet specific goals such as weight gain, maintenance or loss, as well as treatment of diseases. However, in the search for the perfect diet, do not become overly greedy, picky or even fearful of certain foods, which is a problem in itself that can lead to disgruntled dining companions or disordered eating behaviours. There is no such thing as the perfect diet, but it is possible to be mindful about eating every day until it becomes natural to know how much and what type of food to eat and that will help you to know what your body is ‘telling’ you about what is healthful.

 

References

Lieberman, M. A. (2008). Marks’ Basic Medical Biochemistry: A Clinical

Approach. Lippincott Williams & Wilkins.

Whitney, E., & Rolfes, S. R. (2007). Understanding nutrition. Cengage Learning.

 

 

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