The whole idea behind the fat-burning zone is that if you exercise at a particular heart rate (around 60-70%), you will burn a higher percentage of calories from fat. Although true, this is no good if I’m trying to lose fat. The lower your heart rate, the higher the percentage of calories burned will come from fat.
The key to this sentence is “higher the percentage”. You actually burn the highest percentage of calories from fat while you sleep! Your heart rate is at its lowest at that time. So in theory, if you believe in the fat-burning zone for the best fat loss, you should sleep the fat away. You do after all burn a higher percentage of calories from fat. The problem with this thinking is that while you burn a higher percentage of calories from fat, the total number of calories burned is lower.
That is why for maximum metabolic effect in terms of burning fat, an activity sustained for a shorter period of time at a higher intensity above the metabolic threshold, is preferred to consume the higher amount of calories even thou the higher percentage may not come from fat.
This fact is better explained when we understand how the Kreb cycle works. After glycolysis (oxidation of glucose to pyruvate) takes place in the cell's cytoplasm, the pyruvic acid molecules travel into the interior of the mitochondrion. Once pyruvic acid is inside, carbon dioxide is enzymatically removed from each three-carbon pyruvic acid molecule to form acetic acid. The enzyme then combines the acetic acid with coenzyme A, to produce acetyl coenzyme A, also known as acetyl CoA. Once acetyl CoA is formed, the Krebs cycle begins. The Krebs cycle, or citric acid cycle, was put forth to account for the oxidation of carbohydrates. Of course, later the acetyl derivative (a compound formed in fat degradation) was identical to the compound formed by the oxidative decarboxylation of pyruvate, proving that the Krebs cycle also serves for the oxidation of fats. Within the cell, the Krebs cycle takes place inside the mitochondria or "power plant" of the cell and provides the energy required for the organism to function.
In the absence of carbohydrates, Acetyl coa does not bind with oxaloacetate which is normally what occurs in those with adequate glucose. However, in those with ketosis (lacking glucose so fats are used to make energy as ketones ), there is a need for oxaloacetate to be converted into glucose by gluconeogenesis. With no oxaloacetate, the lonely acetyl coa becomes converted into ketones. These bodies are then released into the blood and used as energy during higher intensity exercise.
Strictly speaking, the terms "aerobic" and "anaerobic" refer to the presence and absence of oxygen, but most of our cells prefer to get their energy by using oxygen to fuel metabolism. During aerobic exercise, muscle cells can contract repeatedly without fatigue. During anaerobic or non-oxygen conditions (i.e., higher intensity exercise), muscle cells must rely on other reactions that do not require oxygen to fuel muscle contraction. This anaerobic metabolism in the cells produces waste molecules and result in fatigue.
The problem with the terms "aerobic" and "anaerobic" when applied to exercise is that we actually never switch from total aerobic to total anaerobic metabolic conditions. In reality, the more intensely we exercise, the greater the need for anaerobic energy production. Consequently, it is best to view the terms aerobic and anaerobic as transitions in metabolism, where the proportion between aerobic and anaerobic metabolism changes depending on exercise intensity.
At rest, we rely on aerobic metabolism to fuel almost all our body's needs for energy and as we start to exercise, the increased energy needs of muscle contraction require that we increase our breathing and oxygen intake. So long as we increase our exercise intensity slowly, we can maintain our muscles' dependence on aerobic metabolism, and we don't experience symptoms of fatigue.
However, as exercise intensity increases, the need for energy release eventually exceeds that which can be supplied by aerobic metabolism. Our muscles simply need more reactions to support the energy demand. Therefore, anaerobic contribution to metabolism increases. This metabolic threshold represents the exercise intensity where we start to produce those waste products of anaerobic metabolism that can eventually lead to fatigue.
Known for her ability to deliver highly effective and challenging workouts while making them feel enjoyable, this former elite fitness and bodybuilding competitor is an experienced Personal Trainer with a proven record of getting results! In addition to Personal Training and several other certifications and training through a number of professional organizations, Renita is a success story herself and continues to inspire and motivate everyone she meets! When you make a commitment and focus your mind on any endeavor, anything is possible. Being fit can make you feel alive and take you beyond your wildest dreams. Anybody, given the proper guidance, motivation and support can achieve anything they put their mind to! I couldn’t ask for a better career, I can’t imagine doing anything else! The feeling of knowing I’ve helped someone else. That’s about as rewarding as it gets! I am passionate about helping others achieve overall better health and fitness. When working with individuals and groups I’m so thankful for having the chance to do what I really love; to connect with people through exercise and nutrition. We all want to feel better about something and it can all start with you feeling good about yourself. Fitness and good nutrition have a huge impact on how we feel and that can transfer to our thoughts and choices we make in life. The satisfaction I get seeing people progress toward and then exceed their personal goals surrounding health and wellness is huge for me. It pains me to see so many people struggling with things like weight, fat and chronic low energy. It’s a choice and I’m happy to be the conduit for healthy choices people are making. I love working privately in the comfort of my client’s home – or with small groups to adapt movement to suit a person’s specific needs for optimum results.