Thread by @akhileshutup, You can ignore this thread if you are aware of how our [...]

You can ignore this thread if you are aware of how our body uses, stores and burns energy.

Energy Metabolism 101 ↴

Weight management becomes easy, fun and interesting if we know how our body uses the food we eat. I will try to cover in short my learnings from @PowerDNS_Bert's lessons. ( https://berthub.eu/metabolism/index.html).

This thread is divided into 4 parts:

1. Food and Fuel
2. Transport and storage of fuels
3. Conversion of energy
4. Expenditure of energy

1. Food and Fuel
Our body is like a machine which needs some form of energy to run. Energy comes from fuel. The food we eat contains metabolically active(reactions occurring in cells) ingredients that can be used as fuel.

Metabolically active ingredients from the foods are:
- Fat
- Fibers
- Long carbohydrates
- Shorter carbohydrates ('sugars')
- Proteins

With the exception of fibers, all these carry energy. Fat contains 9 kcal per gram, carbohydrates and proteins in the order of 4.

Fibres do not directly energy but here are indications that they may power intestinal bacteria which help you digest other food. In other words, they can be used to extract 'fuels' from the food we eat.

Your body can extract at least the following three kinds of fuel from what you ingest as food:

- Fatty acids
- Glucose
- Amino acids

The conversion of previously mentions ingredients to these 3 fuels is:

- Fat -> fatty acids
- Long carbohydrates -> shorter -> glucose
- Shorter carbohydrates ('sugars') -> glucose
- Proteins -> Amino acids

2. Transport and storage of fuels

Let us now look at how they are stored and transported to the places actually expending energy. To reiterate, once digested, the following fuels are available:

- Fatty acids
- Glucose
- Amino acids

Fatty acids: Almost all cells can store fatty acids and be transported into bloodstream. In absence of enough cells, your body can easily generate special 'adipocytes' - building blocks of adipose tissue - store fatty acids in the form of triacylglycerol in thighs and stomach.

Fun-fact: Our body easily stores tens of kilos of fat each kilo of fat can power an adult enough energy to survive for a month.

Glucose: It is a very small molecule and is easily transported from cell to cell throughout the body.

This motility - the ability of an organism to move independently, using metabolic energy - is not very well suited for actually storing sugars so for storage sugars are converted to glycogen(which consists of lots of smaller glucoses).

As glycogen, sugar is stored in the liver and in muscles. The glucose travels rapidly into the bloodstream so this makes is it easy for the body to utilise the glucose. However, this comes with a limit.

Average weight people will generally have in the order of 5 grams of glucose in their blood at any one time. Levels above 10 grams are considered too high. This means that a regular candy bar, which contains in the order of 30 grams of sugar, poses a great challenge to the body.

When glucose arrives in excess of the aforementioned 10 grams the body releases insulin which instructs the liver and muscles to absorb glucose from the blood. Furthermore all parts of your body which can run on glucose start doing so. The burning of fatty acids is reduced.

Longer(also called as complex) carbohydrates cannot transfer to the bloodstream and must be converted first, which can take quite some time.

The delay thus incurred is actually a good thing because it makes sure that the blood isn't flooded with glucose, obviating the need for insulin release and other measures.

Amino Acids: Can be converted into muscles or cells or lots of other things, which can also be broken down again into proteins or even amino acids.

Proteins are broken down to amino acids in the intestine and then brought to the liver, where they are partly reassembled and partly released into the bloodstream. Compared to glucose, a lot of protein is available in the blood. Around 100gms.

3. Conversion of Energy
Once the energy ingredients are converted into fuels and stored, they are available for expenditure or conversion. The actual energy currency is ATP.

Nearly all bodily processes do not run on the fuels mentioned earlier. They run on the conversion of ATP to ADP. So why ATP? Why not store energy as ATP directly skipping what we discussed in 3? ATP might be too active to be suitable for long term storage.

4. Expenditure of energy

Even if we are doing nothing, we are constantly spending energy. This is called Basal Metabolic Rate (BMR). Eg. Pumping of blood around. Then there is the brain, which always requires a lot of energy, even when not thinking.

The body spends this energy with a 'strategy.' It likes when the source of fuel/energy is continuous. It sees the already stored energy(read fat) as the last resort. This is the reason why we feel hungry if we skip a meal and have a tough time losing weight.

Another way body spends energy is when we exercise. Actually exercising requires surprisingly little energy compared to the BMR.

However, you can easily raise your BMR by exercising - while the exercise itself does not really cost a lot of energy, the bodily infrastructure created for it will. For 24 hours a day onwards.

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