Have you ever wondered what happens when you lose weight? What happens to the fat and where does it go?
The answer is actually quite interesting!
Your body’s favorite energy source comes from carbohydrates. This doesn't mean you have to be eating loads of bread, pasta or even rice to get your energy, vegetables are also an excellent carbohydrate and energy source! When ingested, carbohydrates get converted into glucose, and then glycogen, which is then used by all your cells and organs as life-sustaining energy.
However, any energy that is not used gets transferred to your adipose tissue, or fat cells, where it will remain until such a time that you burn it off. This is done with the assistance of the hormone, insulin, which is responsible for metabolising and storing fat.
* Did you know that the number of fat cells you have is determined in late childhood and that the number remains constant all for the rest of your life? It is only the size of the fat cells that changes, as more and more glycogen, is deposited and stored in your adipose tissue, for ‘later use’.
When your body is deprived of carbohydrates, which means there isn’t a ready supply of glycogen to feed your cells, your body turns to your fat stores as an energy source. Triglycerides, the main constituents of body fat, are broken down into fatty acids and glycerol. This is where it gets a little more technical. From here, any tissues using fatty acids for fuel (such as your muscle fibres), break down the fatty acids to form acetyl CoA in the mitochondria (think of the mitochondria as being your cell’s digestive systems) through the catabolic process beta-oxidation.
So this explains how the energy is created, but what happens to the bulk of the fat?
During the beta-oxidation, many ATP molecules are formed, this is the energy that is used by the cells. The rest of the fat is broken down into H2O and CO2 using the citric acid cycle and the oxidative phosphorylation.
In simplified terms: Fat gets broken down into ATP which is the energy source that fuels your muscles and all the other cells in your body. The rest of it is either exhaled in the form of carbon dioxide (this makes up about 84%) and the rest is excreted through your body fluids.
Kind of cool huh? The human body really is a complex and wonderful thing, isn’t it?