This is When Your Body REALLY Burn Fat

The Role of Digestion System in this story is

Digestion breaks down the large pieces of ingested food to the size optimal to reside outside the cell. Digestion starts in the oral cavity where enzymes start to work on metabolism of carbohydrates and fats.

Food gets transformed into bolus with the help of saliva and enters the stomach. Stomach acid further dissolves the bolus transforming it into chyme (just imagine how this looks like… I saw it couple of times, not a pleasant picture to say the least).

Chyme gets broken into the elements in intestine and finally absorbed into the bloodstream.

This is the initial stage of the metabolic processes inside the body or enzymes driven catalytic chemical reaction. It is what enables the body to develop, propagate, remains its structure and to respond to the environment.

What is the metabolism anyway?

Metabolism is comprised of two main categories of chemical processes: catabolism and anabolism.

Catabolism is using a series of metabolic pathways to break down the organic matter (amino acids, glucose and fatty acids) to be used in energy production through cellular respiration and other similar mechanisms.

Anabolism on the other hand is using that energy to create cellular structure, for example proteins, while one part of the glucose is used as brain energy and for the locomotive system.

Through a series of chemical reactions inside the cell (metabolic pathways), one chemical substance is being transformed into another using the case specific enzymatic sequence where each individual enzyme acts as a catalyst.

In other words, the process that will naturally occur in 70 million years lasts only few milliseconds when enzymes are added to the process.

The body uses macronutrients (amino acids, carbohydrates and lipids) and micronutrients (vitamins and minerals) for everything. When it comes to energy production, it uses polysaccharides, proteins and lipids.

How The Body Produces Energy

 As we said, anabolic processes can be observed as structural while catabolic ones as destructible. Catabolic processes provide with necessary energy used in anabolism, for example in cellular development.  

How that works is pretty simple. Large molecules are residing outside the cell and being broken on even smaller pieces (polymers) to be absorbed by the cell. Inside the cell, polymers are broken to even smaller fragments (monomers). Example of monomer is acetyl-coenzyme-A, a molecule responsible for the process of releasing the chemical energy.

Cells are using monomers to create new polymers (building blocks) or to break them through the process of oxidation to release the energy. One part of that energy is lost in heat but most of it is used in a synthesis of adenosine-triphosphate (ATP) – the monetary currency of energy in body.

But ATP cannot be stored. In any given time there are approx. 5 grams of ATP in the body. However, body will keep recycling the molecule and use the equivalent of the entire body mass of it in one single day.

Activation of stored fat

Fatty acids stored in adipose (fat) tissue acts as energy reserves. Since they cannot breach the blood/brain barrier, the excess, not used directly, is being converted into the lipid drops within the adipocytes.

Now the trick is simple. Body will always keep the essential levels of stored glucose for brain. So liver and muscles will use stored fatty acids when body is in a state of rest. In other words, stay low with ingestion of carbohydrates (low carb diet) and you’ll force the body to use fat instead.

This is why we are collecting fat tissue because the body prefers carbohydrates and glucose in particular for energy production. And when glucose (glycogen) levels are low and body needs energy, epinephrine and glucagon will be dispatched to connect with their specific receptors on a membrane of adipocyte. This will activate specific enzymes on that same membrane which in turns activates messengers (caffeine is a known messenger).

At the end, these triglycerides (triacylglycerols) are being metabolized into fatty acids and glycerol. Fatty acids are used for energy and glycerol goes to the liver to re-synthesize triglycerides. 

So you see…you can lie down and burn fats. Why sun tanning? Energy is needed in a production of vitamin D in your skin. Two flies with one stroke!