Thanks
Any info on this?
Also, from what I have learnt - The body has 3 main fuel sources - Carbs, Fat, Protein.
How do I know what is being burnt at a specific time? I obviously want most of the burn to come from fat stores but is there a way to condition your body to burn fat and leave the other 2 sources.
Would doing cardio on an empty stomach tap into fat stores immediately?
I've also been lifting weights and I'm seeing some results from that. Is there a way to get your body to NOT burn muscle as a fuel source?
Much more complicated than that.
Carbs, fat and protein are macronutrient types that are used by the body for different things. Certain fats are called essential fatty acids because they are essential to the survival of the body. These include your omega 3 and omega 6 fatty acids. They aren't needed for energy (although essential fatty acids can be converted into energy if need be), they are needed for many essential body processes to function.
It's the same with essential amino acids. Protein is made up of amino acids, some of which are essential to our body because we cannot make them ourselves, and need them from our diet. Amino acids are then used for cell creation and repair. This is why bodybuilding diets are typically so high in protein - a lot of protein is needed to support the growth of muscle. Protein can be converted into glucose for energy, but that is only if there is nothing better for the protein to do (for instance, repair a muscle). Unused protein can be converted into glucose.
Carbohydrates are not needed except for energy - this is why they are not considered essential. Carbohydrates all end up converted into glucose. Glucose is the body's most immediate form of energy. Your blood glucose is deliberately kept in a certain range by your body - high blood glucose can cause a release of insulin, to shift excess glucose into your cells. A blood glucose concentration that is too high is actually harmful, which is why insulin is so important. Having a high blood glucose concentration after a meal is completely normal, as is the insulin response.
Excess glucose can be converted into glycogen, which is stored in the liver and muscles. Glycogen can be pretty quickly converted back into glucose to be used again. Carbo loading actually refers to stocking up on glycogen essentially. You can store up to around 24 hours worth of glycogen, as far as I know. This depends on your level of fitness. Glycogen is depleted for normal energy needs and obviously for exercise.
Your fat stores are then the last store of energy - long term storage. As far as I know, some fat can be oxidized into glucose, other kinds of fat must be converted into ketone bodies. I suppose that doesn't matter though.
What matters is that, if your body has sufficient glycogen, it has no need to start burning fat. And, muscle is a last resort energy source, only used if you have no glucose and no glycogen and no fat.
There is no way to condition your body to burn fat, no. The only thing you can do is keep your glycogen supplies low by not eating excess carbohydrates and by fasting. Low glycogen levels will mean your body has little choice but to burn fat. Bear in mind that having low glycogen also means you won't have as much endurance. You will get tired faster.