Sources of Energy: Carbohydrates and Lipids

So we’ve covered the star of macronutrients – proteins. But what about carbs and fat? They seem to be the scarecrows of fitness efforts. In fact, they are much needed energy sources. We wouldn’t want to go to the gym, for example, without the proper nutrients to get and keep us going, right? However, we need to be mindful of the kinds of carbs and fat we eat. So let’s dive in and see what we should and should not eat, and of course, why.

Carbohydrates – or sugars and sugar polymers – are carbon (C) molecules bonded to hydrogen (H) and hydroxide groups (OH). They act as energy storage with the potency of 4 calories (or approx. 17.5 kJ) of energy per 1 gram of carbs.

There are four major categories of carbohydrates:

  • Monosaccharides;
  • Disaccharides (composed of two monosaccharides bonded through a glycosidic linkage), such as sucrose, lactose, maltose and cellobiose;
  • Oligosaccharides (composed of 3 up to 20 monosaccharides);
  • Polysaccharides (macromolecules composed of hundreds up to hundreds of thousands monosaccharides), such as cellulose, starch, and glycogen;

The monosaccharide glucose appears in all living cells. It is a monosaccharide with 6 carbon atoms (a hexose), together with fructose, mannose and galactose. Glucose is found in the form of a straight chain or in the form of a ring. The latter is the prevalent form of glucose, and it goes by the name of dextrose.

Some examples of foods with high dextrose contents are honey, corn syrup, sweets and processed foods, as dextrose is a commonly used artificial sweetener. Moreover, try to avoid starch-rich foods (a polysaccharide of glucose), such as white bread, cereals (processed grains), white pasta, white rice and potatoes. If you do eat white rice or potatoes, soak them in cold water for 30 minutes before cooking, as this is said to eliminate the starch.

Lipids are yet another class of organic macromolecules that serve as energy storage (fats and oils), thermal insulation and hormones and vitamins. For every 1 gram of lipids burned approx. 37.5 kJ (9 cal.) of energy are released.

 Vitamins A, D, E and K

Liposoluble (fat-soluble) vitamins such as Vitamin A (cell maintenance), Vitamin D (calcium absorption), Vitamin E (antioxidant), and Vitamin K (normal blood clotting) are essential vitamins, meaning that it is necessary to obtain them from our diets, since they cannot be synthesized in the human body.

Natural sources of these essential vitamins include:

Vitamin ACarrots, baked sweet potatoes, kale, beef liver, cantaloupe, mangos, boiled spinach, (carotenoids);

Vitamin DShiitake and button mushrooms, eggs, salmon, herring, sardines, tuna, catfish, solar light;

Vitamin E – Almonds, sunflower seeds, pumpkin seeds, sesame seeds, hazelnuts, pine nuts, avocado, Swiss chard, spinach, kale, broccoli, parsley, papaya, olives;

Vitamin KKale, spinach, fermented soy, Brussels sprouts, broccoli, scallions, prunes, cabbage and cucumbers;

Fatty acids and Lipid Oxidation

Fats and oils are triglycerides, composed of 3 fatty acids molecules and 1 glycerol molecule.

  • Glycerol is a 3-carbon molecule with a hydroxyl group for each carbon atom.
  • Fatty acids are hydrocarbons with a carboxyl group at one end. Fatty acids can be saturated or unsaturated.

Saturated fatty acids are animal fats. They are saturated because they have the maximum number of hydrogen atoms attached to the carbon chain.

Unsaturated fatty acids derive primarily from plants. They are unsaturated because they contain one or multiple double bonds (monounsaturated or polyunsaturated) which are formed by removing hydrogen atoms from the carbon chain, leading to the formation of free radicals. The higher the degree of unsaturation, the higher the rate of lipid oxidation. This is where antioxidants come into play, fighting the free radicals and preventing oxidation.

Goji and blue berries, pecans, dark chocolate, cinnamon, and turmeric are just a few powerful antioxidants. Other measures include using olive or palm oil for a more stable unsaturated oil, using vacuum-sealing food packaging, and storing your food in a low-temperature and dark environment.

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  1.  MITOpenCoursewear – Chemistry of sports, p. 21-36
  2. Global healing center
  3. Lipid oxidation

Proteins and the 20 proteinogenic amino acids

What’s an athlete’s favorite word? It’s probably protein, right? We all know proteins are fundamental to muscular development. They provide the necessary support, protection, transport, regulation, and movement to the human body.

Stressed for time? If you can only have the quickest read, you can go directly to Summary.

 The birth of a protein

Proteins are macromolecules which are formed through dehydration synthesis reactions leading to covalent bonds between monomers; a multitude of monomers forms polymers. Proteins are polymers of amino acids. Different compositions of amino acids form different types of proteins, with diverse structures and functions.

Proteins are also called polypeptides. Amino acids are covalently bonded by peptide linkages (e.g., a dipeptide is formed of two amino acids). As polypeptides, proteins are multiple-peptide chains of proteinogenic amino acids.

Proteinogenic amino acids are those organic compounds containing the amino (NH2) and the carboxyl (COOH) groups which are capable of producing proteins. There are twenty proteinogenic amino acids, eleven of which are non-essential (i.e., they can be synthesized by the human body and therefore are not imposed in our diets), leaving nine of them, the essential amino acids, as dietary requirements given they cannot be synthesized by the human body.

Protein sources – complete and incomplete proteins

Foods containing the nine essential amino acids are known as complete proteins. These include animal sources (meat, fish, milk, yogurt, whey, eggs), quinoa, buckwheat, hemp seeds, chia seeds, and spirulina.

On the other hand, plant foods are considered incomplete proteins that cannot provide all the essential amino acids. However, specific combinations will complement each other, so just adjust for complementary protein sources in your meal or throughout the day. The rule of thumb when it comes to complementary proteins is combining grains, cereals, nuts or seeds with beans, peas, lentils or peanuts (e.g., peanut butter on wheat bread).



Proteins are macromolecules as polymers of amino acids. Proteinogenic amino acids are those amino’s capable of producing proteins. There are twenty proteinogenic amino acids: eleven non-essential ones and nine essential ones (essential amino-acids are not synthesized by the human body and therefore need to be supplied through diet). These essential protein-builders are most easily obtained through animal products (meat, dairy, whey), quinoa, buckwheat, hemp seeds, chia seeds, and spirulina.

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  1. MITOpenCoursewear – Chemistry of Sports p. 11-16
  2. University of Massachusetts – Nibble Directory