In order to avoid being redirected here to read this, I'm going to post my question here since I've read the sticky several times already.
Can you explain how the fat burning process work[assuming diet and physical activity is in check]? This is what I understand from googling the subject... All physical activity aerobic or anerobic begins with the use of glycogen stores as energy? And it takes up to a certain time[say 20 mins] to use that up? Now this is where I begin to have difficulty finding a common ground between many opinions. Some say this is the point where fat burning begins, others say this is when your body goes into catabolism. So what exactly happens after 20 mins? What's the criteria to optimally set your body into fat burning mode? Specifically, what does a body have to do before it begins utilizing fat? Thanks in advance.
Let's see if I can first clarify some things for you. When you begin exercising, your body utilizes the phosphagen pathway, then the glycolytic pathway (carbs only), and then the oxidative pathway (carbs and fats). The oxidative pathway starts up after about ONE minute of exercise. That means fats begin to get burned almost as soon as you start exercising. During physical activity after that, you will burn a skew of both fats and carbohydrates - at lower intensities, you'll mobilize more fat and use that while at higher intensities, you'll utilize almost entirely carbohydrates.
There's a huge problem with thinking that, if you work out a lower intensities, you'll burn more fat. In all technicality, you will. However, there are many several sources of fats, primarily free fatty acids, muscular fat stores, and then finally adipose tissue (which is typically what people are concerned about). If you're eating at caloric maintenance, all fat stores and glycogen stores utilized will be restored. If you're eating in a caloric deficit, there's a order or priority for the body to restore certain compounds before others. Typically when recovering from endurance exercise, glycogen is the first to be restored, then fat stores, and then muscle tissue is repaired. If an individual is only doing aerobic exercise, then both the glycogen and fat stores will be restored first and foremost. This is why people CAN lose so much muscle while only doing cardio. Muscle repair is a low priority compared to fat stores and glycogen availability, since these are so necessary for good cardio.
However, if you engage in strength training, the load initiates genetic pathways for hypertrophy. This skews the order of priority quite a bit. Glycogen restoration is still very important, but muscle repair becomes one of the body's main focuses. Body fat restoration is less important at that point since there is no benefit for it during strength training. This sounds like I'm saying the body recognizes what's best during each situation: it's not that simple. As you engage in certain activities, there are specific genetic markers, enzymes, and compounds that are expressed that benefit development in response to a stress. This is why I mention to start on a strength training program while losing weight. It will help with fat loss a great deal more, while cardio's effects depend a bit more on genetics.
Now to approach which zone to work in. I feel everybody should work at high, moderate, and low intensities to mix things up. All of them will work to decrease the body fat percentage of an individual in a caloric deficit, especially if the individual is on a strength training program. Eating enough protein, being in a caloric deficit, and working out will be more than enough to burn fat. In my experience, cardio isn't typically where body fat % is decreased the quickest - strength training is. Hope that helps.
Six pack is starting to show, and riding up hill feels slightly easier.
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