The Physiology of Fat loss

Have you ever thought how fat loss happens. I mean if you lose 5 kgs weight where does it go. Do you poop, pee, or sweat? Tiny bit of it yes. Most of it you breathe out. Yes, every breath you take out you lose some fat. Let’s understand how we lose fat by breathing.
The very basic prescription for fat loss is diet and exercise. When we exercise, we start to breathe heavy. If you, do it enough, consistently and if you are patient, you are going to lose fat. Let’s understand how breathing makes us lose fat.
Say you eat some mixed macro nutrient meal. Food that has Carbohydrate, Protein, and fat. The food is not the actual food we eat when it leaves your gut and get into your blood. It will be some form of these macronutrient. If you take your blood out, you don’t see the food but there is protein, fat, or glucose in the blood. Our gut breaks down the food into individual macros. We get some energy doing this process. The blood glucose floating around in the blood is chain of carbons.
Carbohydrates is 6 carbon chain. Glycolysis breaks the 6 carbon molecules to two 3 carbon molecules. Which will further break to two 2 carbon molecules. So, from 6 carbons now we have 4 carbons and lost 2 carbons. In a simple process of breaking down the carbohydrate we lost two carbons. As you breath in Oxygen it mixes with the free-floating Carbon and makes Co2, and we breathe it out. The two 2 carbon molecules further break down through a process called Krebs cycle and at the end we are left with no carbon. If we have oxygen available, you will breathe it out all. So, when we metabolize Carbohydrate all we are left with some energy, Water and Co2 which we breathe out.
Fat works a bit differently. Fat is broken down to triglycerides and fatty acids. A triglyceride is exactly what it sounds like – three glycerides. The backbone of triglycerides is three carbon glycerol. And a bunch of fatty acids. Fatty acids are chain of carbons. The length of the chain determines what type of fatty acid is it. The three carbon goes through the same process as carbohydrates mentioned above. Break down further to two 2 carbon molecules and Krebs cycle and end as Co2 and Water and energy. The long chain of fatty acids goes through process and ultimately breaks down to 2 carbon molecules. Eventually it goes through the Krebs cycle, and we get the same output – lots of energy, water and Co2. The process to burn fat is aerobic. The process to burn Carbohydrate is anaerobic to start with and aerobic to end.
Protein breaks into Amino acids. And further into three carbon chains and two carbon chains. Biproduct of this process is NH2 which we excrete through urine. Breaking protein is also aerobic process. You need oxygen.
When we start to utilize this information and fuels to optimize our exercise, understand carbohydrate is coming directly from the active muscle but fat is coming mostly from the entire body. In other words, say if you are running and start to feel the burn in your calf, you are using the energy coming from carbohydrate in your calf. Energy coming from fat does not happen this way but comes from the entire body. This explains why spot reduction is not possible. If you are doing crunches the fat energy maybe coming from your face or fingers and not just waist. So, when you are, say running, and start to run short of fuel source of carbohydrate from your calf, your energy from fat is not coming from calf but all around your body. So, when fat is needed as a fuel it burns from everywhere. As you can make out logically it takes time for fat to reach the place where you need energy. In other words, carbohydrate in your calf is readily available but for energy coming from fat it takes some time to reach the effected muscle. Knowing this you can decide with related to your exercise protocol when to eat little more carbohydrate or when to go low and eat more fat. 75 kg men with 20% body fat can survive 30-40 days of not having fat as his body will have that much but carbohydrate will be a limiting factor, as you can store only so much within your cell.
Illustration by Kanupriya Singh (Twitter :@_KanupriyaS)from Dr Andy Galpins classroom
Illustration by Kanupriya Singh (Twitter :@_KanupriyaS)from Dr Andy Galpins classroom
Ending it in simple terms, if any excess carbons are there in your body it will accumulate and make you fat. If you breathe out more carbons than you have or intake you will lose fat. Knowing this information how fat and carbohydrate works ca help you design your food and exercise. And always remember you can never outrun a bad diet. So, if your goal is to lose fat remember anything that makes you breathe, makes you lose weight.

November 14, 2021

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