So there’s a lot of talk about how much fat we should eat, or counting our carbs, or making sure we get enough protein in our diets — but what does this all really mean? Before you try to understand nutrition and how your diet will affect your daily life, it might help to break down just WHAT these different chemicals are that we ingest. So, without further ado, let’s begin:
The three materials listed above (carbs, fats, and proteins) are common terms used to describe the three primary energy substrates (fuel sources) in the body. Quite simply put, they’re the things that we actually break down for energy to do work and keep our bodies functioning. All three of these fuels (which I will often call macronutrients) are comprised of varied arrangements of the elements Carbon (C), Hydrogen (H), and Oxygen (O) — in addition to Nitrogen (N) in the case of proteins, but that will be covered later. I’ll give an overview of the different macronutrients below:
(~ 4 Calories per gram)
Carbohydrates are sugars formed from a combination of Carbon, Hydrogen, and Oxygen atoms, with chemical formulas generally carrying a ratio of 1:2:1 (e.g. Glucose, or blood sugar, has a formula of C6-H12-O6). You will find between 3 and 7 carbon atoms in any simple sugar. Carbohydrates are often categorized by the number of simple sugars contained within them: Monosaccharides (1), Disaccharides (2), Oligosaccharides (2-10), and Polysaccharides (3+, up to thousands). Glucose would be a monosaccharide. Sucrose (table sugar) would be a disaccharide since it is composed of two sugars, Glucose and Fructose. Examples of others will be examined later.
The majority of carbohydrates in the human diet come from plant sources. One notable exception is lactose (milk sugar), which obviously has animal origins.
It is important to know that while we get most of our carbohydrate intake from plants, we don’t store them the same way. In plants, carbohydrates are stored in the form of starch. When you hear diet experts use the term “complex carbohydrate,” that’s generally what they are referring to. Humans (and animals in general) store carbs in a molecular form known as glycogen. Simply put, glycogen is a branched chain that can contain hundreds and hundreds of glucose molecules. More information on glycogen and its metabolic function will come in the future.
Fiber is the structural polysaccharide (remember, MANY simple sugars linked together) that is not classified as starch. It’s the most commonly found organic substance on earth! But more important to us at this point is its role in diet. It’s divided into two main categories: water-soluble and water-insoluble. Soluble fiber is known to have some ability to lower LDL cholesterol and improve digestive health, and it is found in foods such as peas, brown rice, carrots, oats, and many fruits. Insoluble fiber includes structural cellulose such as that found in wheat bran, and while it has not been linked to the same health benefits as its water-soluble cousin, it HAS been suggested that insoluble fiber may help with sugar and insulin sensitivity. Note that many source foods contain both categories of fiber, so one cannot really oversimplify by classifying one food as ONLY one or the other. As a final note — there are different types of fiber within these subsets that I can get into in further detail later!
Energy Metabolism – Carbohydrates are the most quickly utilized of the three macronutrients. That is to say, carbs can be burned more quickly for energy than either fats or proteins, which carries important implications for exercise performance at higher degrees of intensity. They are readily broken down and utilized for energy through a process known as GLYCOLYSIS (which I will explain later). While all three substrates are important for a number of processes in the body, including producing energy for exercise, carbohydrates are uniquely suited for the most intense jobs.
Glycogen is a long, branched-chain polysaccharide that comprises the majority of the carbohydrate stores in our bodies. With the exception of a few grams of glucose that are floating around in our blood at any given time, the vast majority of the ~500 grams we store is found in our liver and muscle cells. Glycogen’s role in energy production and exercise will be explained later.
(~ 9 Calories per gram)
(~ 4 Calories per gram)