Carbohydrate Metabolism

We saved the best macro for last: Carbs! In this article, we’ll go over carbohydrate metabolism and how we utilize carbs for physique and performance enhancement.

Carbohydrate types

Let’s start with the basics of carbohydrate nutrition. Just like protein and fats, carbohydrates come down to being made of molecules. The three main types of carbohydrates are monosaccharides, disaccharides, and polysaccharides.

Monosaccharides are the simplest form of sugar and include glucose (an essential energy source for nerve cells, red blood cells, brain cells, etc.), fructose (sugar found in most fruits), and galactose (a derivative for lactose).

Disaccharides are essentially pairs of monosaccharides but are often named maltose, sucrose, and lactose.

Polysaccharides are the most complex in structure out of all the carbohydrate types: glycogen (the storage form of glucose in the body), starch (storage form of glucose in plants), and fiber (structural parts of plants).

Each of these three classes of carbohydrate vary by size and structure. Monosaccharides are what we would call the simplest form of carbohydrate, that is very quick and easy for our bodies to break down and are the best forms of quick energy. Polysaccharides are the most complex form of carbohydrate and take the longest time for our bodies to break down and digest (if they can at all). This is why foods that are high in fiber are often very satiating as fiber is largely not digested and delays gastric emptying. We encourage our clients to hit a certain fiber goal along with their carbohydrate goal because fiber can help to improve cholesterol, control blood glucose, improve digestion, and manage weight through improved satiety. A polysaccharide that you have probably heard of before would be glycogen. Glycogen is simply the storage form of glucose. Each gram of glycogen is stored with 3 grams of water. Two major sites of glycogen storage are the liver, and the skeletal muscle. The breakdown of glycogen is how we access carbohydrates for energy during periods of exercise or fasting.


Maintaining blood glucose homeostasis

Our bodies have a robust regulatory system for maintaining blood sugar regularity. However, if used and abused too much this regulatory system can “wear out,” and often lead to insulin insensitivity and in worst cases, type 2 diabetes.

Glucose enters the blood stream, insulin is signaled to leave the pancreas and regulates blood sugar levels by moving the glucose to be delivered to the liver, skeletal muscle, and brain for energy. Instances of chronic overfeeding can downregulate the sensitivity of the signal to insulin, requiring more glucose in the blood to get insulin to do its job. In instances where insulin stops responding, is where individuals run the risk of developing type 2 diabetes.


Glycemic response

Glycemic response refers to the speed of glucose absorption. Carbohydrates are ranked on an index called the glycemic index based on their ability to increase blood glucose levels. Foods that are high on the glycemic index are often simple carbohydrates that are quickly broken down by the body and are often low in fiber. Low glycemic foods do not elevate blood glucose levels as much, take longer for the body to break down, and are often high in fiber.

So, should you be eating carbohydrates that are low on the glycemic index? At face value, it seems like a great idea because we want to avoid chronically high levels of blood glucose to mitigate the possibility of developing type 2 diabetes. However, the research shows that within a caloric deficit, and with enough exercise you can consume high glycemic index carbohydrates and still be perfectly healthy. A study that looked at 3 different diets (high glycemic, low glycemic and high fat) found that all groups lost weight and improved insulin sensitivity independent of diet composition. Therefore, in this instance, lowering glycemic load and index did not provide added benefit to energy restriction in promoting weight loss. However, in any case, context is key. If you are not very active, then it is likely in your best interest to manage your blood sugar levels through low glycemic carbohydrates.


Is sugar as bad as we think?

Anything in excess is as bad as we think. Therefore, the answer here is dependent on context. Athletes who have high demanding performance schedules may benefit from higher glycemic carbohydrates that are often found as simple sugars. However, someone who lives a more sedentary lifestyle and sits at a desk for 8 hours a day should be weary of consuming high amounts of sugar, as high sugar intake in sedentary populations is linked to obesity and chronic disease.


Carbohydrates for Physique Athletes and Performance Athletes

The performance athlete relies on carbohydrates for energy and recovery throughout training sessions, races, competitions, and meets. During high intensity exercise, carbohydrates are the body’s primary source for energy. Fat breakdown and mobilization is a slow process, therefore if an athlete is running a 200m sprint their body is going to tap into the quickest energy source it can perform in 35 seconds or less. Fat oxidation typically cannot support muscular contract that requires more than 60% of someone’s VO2 max (the maximal ability your body can utilize oxygen during exercise). Therefore, power athletes, strength athletes, and endurance athletes often benefit from the consumption of carbohydrates for higher intensity exercise.

The physique athlete also relies on carbohydrates for energy and recovery during training sessions. However, the physique athlete also relies on carbohydrate manipulation for body re -composition and fat loss. As it was mentioned in the fat metabolism article, insulin serves as a gate keeper for fat loss. If circulating levels of insulin (the hormone released when blood glucose increases with carbohydrate intake) are high, then lipolysis (fat breakdown) and fat oxidation (fat burning) are inhibited. Therefore, the physique athlete must play the balancing act of keeping carbs high enough to support their training regimen but not too high as to inhibit fat loss. This is where a great coach who understands metabolism can really shine for the body building athlete, as maintaining muscle and losing body fat to be competitive on stage is a dance between having enough calories to maintain muscle for as long as possible but manipulating macronutrient targets to elicit fat loss without muscle loss.


Having a coach that not only understands how carbohydrates effect a client’s goals, but how the specific diet history, genetic make-up, and lifestyle impact the macronutrient composition that each client needs is key to being successful. Luckily, all the coaches on Team LoCoFit are well versed, well-educated, and well-practiced on understand the nutritional needs for each client.


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