Dietary Fats and Barbell Training

Fat is a word whose mention is a double-edged sword in today’s society. We love it in our food, we hate it on our bodies. Like most nutrients, it does not suffer from a lack of information, but rather a lack of correct information. The wordfat originates from the Old English verb “fættian,” which means to cram or stuff, with the past participle “fætt” defined as “fatted,” “plump,” or “well fed.” Today the term “fat” is commonly used to describe both bodyfat or dietary fat. The more precise term to use in that context is triacylglycerol (TAG), commonly referred to as triglyceride. This paper will focus primarily on dietary fat, its role in human physiology, and its impact on barbell training.

Lipids

Unlike carbohydrates and proteins, which are terms that define entire classes of macromolecules, the term “fat” refers to a subclass of the molecules known in chemistry as lipids. Unlike carbohydrates and protein, lipids are chemically diverse molecules, making their classification difficult. Their ability to dissolve in organic solvents is the most notable feature that differentiates them from other macronutrients. Unfortunately, other molecules share this feature, making it incorrect to rely solely on this classification. Several other classification methods exist but are subject to similar issues. Consequently, the simplest approach is to restrict lipids to those of nutritional relevance and organize them based on structural and functional similarities.

Fatty Acid Classification

Fatty acids are the simplest of lipids. Chemically, they have a methyl group (CH3) on one end and a carboxylic acid (COOH) group on the other end of a chain of carbon/hydrogen units. They are similar to amino acids in that some are produced endogenously, and others must be obtained from dietary sources. Just as amino acids are necessary to form proteins, three fatty acids are required to form a triglyceride, the more stable storage form of fat. Fatty acids serve as the primary energy source within the triglyceride molecule. They can be oxidized for energy or bound to glycerol and stored as triglyceride for later use.

There are four methods of classifying fatty acids: degree of chain length, saturation, essentiality (the inability to synthesize a necessary fatty acid makes it necessary to ingest it), and geometric isomerism or shape (i.e. cis or trans – the geometric configuration of the molecule).

• There are short- (≤4 carbon), medium (6-12 carbon), long-chain (13-21 carbon), and very long chain (≥22 carbon) fatty acids, with medium- and long-chain being more abundant in dietary sources.

• Since the late 1980s, the term saturated fat became familiar to everyday consumers. Fatty acids are either saturated (no double bonds between carbon and hydrogen atoms) or unsaturated (double bonds are present), with unsaturated fats further classified as mono- or polyunsaturated (i.e. having a single double bond vs multiple double bonds). Think of a double bond as a place where another hydrogen atom can fit to one of the carbon bonds: a fully “saturated with hydrogen” fatty acid has no room for any more hydrogen atoms. Fats with a high ratio of saturated fatty acids are solid at room temperature and fats with a higher proportion of unsaturated fatty acids are liquid at room temperature.

• Essential fatty acids (EFAs) must be obtained from food, and non-essential fatty acids can be synthesized in the liver. Linoleic acid and alpha-linolenic acid are the two primary essential fatty acids that must be obtained from the diet, since they cannot be synthesized.

• Lastly, unsaturated fatty acids can be further classified as cis- or trans-isomers, with most naturally occurring unsaturated fatty acids existing in the cis configuration. Put simply the makeup is identical but the three-dimensional arrangement differs. A trans fatty acid is geometrically straight, while a cis fatty acid is bent.

Since trans fatty acids were a hot topic years back, they are worthy of further discussion. Trans fatty acids exist as the result of biohydrogenation by gut microbes, or commercial hydrogenation by food manufacturers. Briefly, hydrogenation refers to the process of treating a cis unsaturated fatty acid with hydrogen gas to either shift the geometric configuration (partial hydrogenation) to form a trans fatty acid or remove all of the double bonds (full hydrogenation), resulting in a saturated fatty acid. The end result is that a liquid oil, high in unsaturated fatty acids, becomes a solid at room temperature. This increases the hardness, plasticity, and melting point of the product and enhances the stability, thus extending shelf-life and making food production more cost-effective.

Trans fatty acids exist naturally in small amounts in plant oils, as well as dairy products, lamb, and beef. They are more commonly found in processed foods, although now in trace amounts due to regulatory changes. Specifically, a food label may say “trans-fat free” but may still have partially hydrogenated oils listed on the food label because the amount is below a target threshold.

Essential Fatty Acids

Unsaturated fats can be classified by the number of double bonds present and the location of the first double bond. The most familiar system in the nutritional sciences uses a “trivial” or common name and includes the term “omega” to designate the position of first double bond when counting the number of double bonds from the end of the molecule containing a methyl group, or omega, end of the fatty acid. Omega-3, omega-6, and omega-7, and omega-9 fatty acids naturally occur in the food supply, with omega-6s accounting for the majority of fatty acids in the American diet.

Linoleic acid (omega-6) and alpha-linolenic acid (ALA, omega-3) are two essential fatty acids that must be acquired from dietary sources (see Table 1). Humans lack the necessary enzymes to desaturate (i.e. add additional double bonds/remove hydrogen atoms) fatty acids beyond the 9th double bond. However, humans can lengthen fatty acid chains via enzymatic reactions (e.g. the omega-6 and omega-3 pathways).

For example, linoleic acid can be converted to arachidonic acid (20 carbons, 4 double bonds) and ALA can be converted into eicosapentaenoic acid (EPA, 20 carbons, 5 double bonds) or docosahexaenoic acid (DHA, 22 carbons, 6 double bonds), which are omega-3 fatty acids found in marine fish. Arachidonic acid is the predominant fatty acid in cell membranes, which means that the structural integrity of our cells depends on it. Consequently, deficiencies resulting from chronic exposure to a very low-fat diet can include poor growth in children, skin abnormalities, and hair loss to name a few. Arachidonic acid and EPA are released from the cell membrane and used to produce eicosanoids, which are molecules that signal a variety of physiological responses.