Metabolism is defined as all of the chemical processes that occur in the body, and is broken down into two categories: anabolism, or the building phase, and catabolism, or the breaking down phase. Energy metabolism ultimately utilizes a series of chemical reactions to breakdown the foodstuffs we consume, such as carbohydrates, fats and proteins which are ultimately used for energy, or stored in the body. Understanding which metabolic processes use fat more efficiently is useful in achieving both your body composition goals and the necessary energy processes that will get you there.
ATP and Energy
ATP stands for adenosine triphosphate, and is a molecule in the body that stores energy. The body relies on the rebuilding of ATP molecules once they are catabolized for energy needs to continue. During exercise, the rebuilding of this molecule is necessary to facilitate the desired training intensity, time and frequency, so that the body creates different metabolic pathways to accomplish this while providing a continuous supply of energy.
The Oxidative Pathway
The oxidative pathway is the only pathway that results in fat catabolism. Beta oxidation is the commonly referred to as the term for the catabolism of fat, and it is a long process. ATP is ultimately produced in the electron transport chain of the body, through the oxidation of coenzymes and ADP, or adenosine phosphate. Once this process is complete, 38 molecules of ATP are produced to be used for fat catabolism.
The Respiratory Quotient
The respiratory quotient is a method that was developed to specifically help you target which substrate of energy you are using, whether it be carbohydrates, protein or fat. Simply put, the respiratory quotient is a measure of the ratio of the volume of carbon dioxide expired, to the amount of oxygen consumed. This method is useful in determining fat catabolism and ATP expenditure because the amount of oxygen used will be different for fat versus other macronutrients. The respiratory quotient for fat catabolism is 0.7, where the volume of carbon dioxide expired is divided by the volume of oxygen utilized. Fat has a lower value than other macronutrients since fatty acids require oxygen for catabolism.
Training Intensity
Training intensity also affects fat catabolism. As your physical conditioning improves, your respiratory quotient is lowered, which will mean more fat catabolism for a longer period of time. This is why understanding your necessary dietary intake, along with the right combination of exercise is important depending on your body composition goals, or the chosen sport or activity you are training for. New technologies have emerged which test various elements of your metabolism, including the balance of protein and nitrogen, which is necessary for growth and repair, along with hormone levels such as testosterone and cortisol, two key players in fat catabolism, muscle growth and energy expenditure.
References
- "Fitness: The Complete Guide"; Dr. Frederick Hatfield; 2009
- "Exercise Physiology: Basis of Human Movement in Health and Disese"; Stanley P. Brown, Wayne C. Miller, Jane M. Eason; 2006
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