The Science Behind a Short Term Lower Carb Diet

 The creation of energy involves a complex series of chemical reactions- in simple terms the macronutrients (carbohydrate, protein and fat) can all be broken down to make energy. It is important to note that both protein and fat are essential for energy production, growth and mainatainance of the body’s structures.

Why something happens in the body as a result of training and nutrition has always been the key factor when I look to access the best way that I work with people to reduce body fat. One such popular way is low carbohydrate dieting. Now lots of diets work for different reasons but in this post I wanted to examine why reduced carbohydrate intake is an effective dieting strategy as well as the science behind this approach.

Carbohydrate is the only macronutrient not essential for life though its role in the upkeep of a healthy metabolism means that severe restriction over a prolonged period is unadvisable. Carbohydrate is utilized through a process called glycolysis where after dietary carbohydrate is broken down to glucose it is available to be used for energy. Protein can also be utilized for energy from dietary sources as well by catabolism (breaking down) of lean muscle tissue in to amino acids that can be utilized as energy. This is not the body’s primary mechanism of energy as it involves a high amount of energy to breakdown protein; therefore carbohydrate and fat are the predominant sources of energy for the body.

When energy supplies become sparse in your bloodstream, the body detects this and fat reserves are utilized. The burning of body fat is traditionally termed oxidation as the body produces energy when fuel is reacted with oxygen to create energy. At rest and very low intensity exercise approximately 70% of the energy produced is derived from fats. Most tissues in the body can use triglycerides as an energy supply apart from the brain (though it can use ketones manufactured in the liver from triglycerides).

Under periods of sever calorie restriction (especially carbohydrates) production of ketones to use as fuel increases. When high amounts of fat is being broken down (usually due to severe calorie depravation) there may be no immediate use of these (this can be associated with an acidic smell or bad breath). This is important, as fat cannot be converted into glucose, but it can provide fuel for the muscle and brain in the form of these ketones- it shows that energy can be produced by the body when limited carbohydrate is unavailable. It also highlights that in the short term this can be an effective mechanism to invoke an increased rate of fat breakdown in the body.

Published by ianmellis

Ian Mellis MSc. CSCS is the co-founder of Results FAST ( in Ware, Hertfordshire. Specialising in athletic development, physique improvement and injury rehabilitation he provides personal training, strength and conditioning and nutrition coaching for motivated exercisers and those looking to make a long term change to their health, fitness and performance.

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