Taking Control of Your Dietary Composition Part 9

Three chemical compounds provide the energy in the foods and beverages we consume. These substances are called macronutrients because we need them in large amounts in order to achieve growth and maintain health. The three macronutrients are protein, carbohydrate and fat with the distinction depending on the compound's chemical structure. Carbohydrates contain carbon, hydrogen and oxygen in a 1:2:1 ratio whereas fats contain the same elements in a combination that favors carbon and hydrogen. For example, the fat stearic acid has 18 carbon atoms and 36 hydrogen atoms, but only two atoms of oxygen. The potential energy in macronutrients becomes available in the body when bonds between carbon and hydrogen are broken, so this structural difference means that fats are more densely energetic compared to carbohydrates. In fact, fats contain no less than nine kilocalories per gram compared to carbohydrates, which only provide four. Proteins are formed from combinations of 22 amino acids that comprise the same three elements, but unlike the other macronutrients, amino acids also contain nitrogen. This element is essential for building body proteins necessary for immune function and tissue repair (for example, after resistance training when increased muscle protein breakdown creates the need for additional synthesis) and is also involved in the making of enzymes, hormones and nucleic acids that hold our genetic blueprint. However, nitrogen does not contribute energy to the diet, so when protein (either dietary or bodily) is broken down for energy, only the carbon-hydrogen bonds are accessed. Much like carbohydrates, protein provides four kilocalories per gram.

In previous installments, I have stressed that changes (or lack thereof) in body fat stores are solely due to energetic balance (i.e., how many kilocalories you consume compared to how many you expend). With this in mind and given the aforementioned differences in energetic density, if your goal is to operate at a caloric deficit that facilitates fat loss without being hungry, it's logical to ingest the least amount of energy with the most bulk intake, which means that carbohydrates and protein are better options. This forms the basis for the common recommendation of the low-fat diet for fat loss. What is more, high intake of certain types of fat has been linked to heart disease, cancers and diabetes, so this fat-loss dietary strategy also appears to make sense for health purposes. However, ingesting too few kilocalories in the form of fat is also unhealthy because dietary fat is important for promoting the absorption of fat-soluble vitamins and forming hormones and cell membranes. Furthermore, the right types of fat can protect your heart from the damage that the wrong kinds inflict, so drastically restricting all fat intake (for example, as was the case with popular diets of the '80s) is not the way to go. More recently, the prevailing belief has shifted and diets that involve low carbohydrate intake along with higher protein and fat ingestion have become popular for fat loss. The extreme carbohydrate restriction that characterizes these diets results in depletion of body carbohydrate stores (i.e., reduced liver and muscle glycogen), which prevents the complete breakdown of fatty acids. This results in a condition known as ketosis, which is characterized by the accumulation of acidic metabolic byproducts (ketones) in body tissues and fluid.

Ketosis carries a negative stigma because it is associated with a life-threatening condition in patients with type I diabetes. These individuals lack the hormone insulin which, when uncontrolled, results in an imbalance that leads to increased glycogen breakdown and fatty acid mobilization. This causes ketone formation. However, being that blood glucose is excessively high in this circumstance and insulin-related feedback loops that prevent excessive ketone formation are absent, ketone accumulation is much greater during this type of ketosis (diabetic ketoacidosis) compared to that which occurs when ketosis is purposely induced via dietary manipulation (dietary ketosis). Consequently, extending the negative stigma to the latter, at least in this regard, is unwarranted. But whether this strategy is a superior alternative for fat loss compared to one with more balanced intake (for example, as per U.S.D.A. recommendations of 10-35% of energy from protein, 45-65% from carbohydrates and 20-35% from fat) remains a matter of contention.

Given that body fat will only be reduced if an energetic deficit is present, there is no justification for the belief that a ketogenic diet that provides the same amount of energy as a more balanced approach will be more effective for promoting fat loss. In other words, if your current caloric maintenance level is 2,000 kilocalories per day, no diet that provides 2,000 kilocalories per day can facilitate fat loss even if macronutrient balance causes ketosis to occur. Conversely, given that there are 3,500 kilocalories of energy in a pound of fat, a diet that provides 1,500 kilocalories per day will bring fat loss to the tune of one pound per week regardless of whether ketones are produced. This means that ketogenic diets should offer no advantage when trying to lose body fat. But anecdotal evidence suggests that there are individuals who have found success with this approach and recent research by Johnstone et al. in the Journal of Clinical Nutrition helps to explain why this might be the case. 

This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.




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