The Cause of Obesity Part 4: Eating Fats

If nutrients were celebrities, fats would constantly be in the news. In and out of the courtrooms trying to prove its innocence. Paparazzi swarming. Stating “no comment” to all questions. Driving off in tinted SUV’s.

Everyone seems to have an opinion but, most don’t have a solid grasp of the basics so let’s take a look at the convoluted world of fats. #nerdup

If you haven’t already, have a read of my prequel post on carbohydrates here.

So, what is a fat?

Triglycerides: You will never look at them the same

Fats can come in a number of different forms. The main ones are triglycerides (TAGs), phospholipids and cholesterol. Although it is not the focus of this post, it is worth knowing that fats play a much bigger role than simply causing people to develop love handles. They actually help to make up all cell membranes i.e. the outer layer of every single cell in our body.

“Yeeeer but, like so what?” – Simon Cowell.

Well Simon, they store and release energy, keep us warm, help to absorb nutrients, help to form hormones…the list goes on.

The majority of this post will cover TAGs. TAGs are made up of glycerol and fatty acid building blocks. In each TAG, the glycerol forms a backbone and 3 fatty acids join themselves to it. If you turn your head and squint a little bit, it almost looks like 3 sperms stuck to a Kit Kat. I dare you to tell me it doesn’t.

So, what happens when you eat fat?

You enter the drive through at McDonalds. You ask for a double cheeseburger happy meal. You thank the pre-pubescent 13 year old boy for serving you #minimum wage life. Along with a concoction of processed and mystery ingredients, fat enters your body. It’s game time.

TAGs are broken down into their building blocks by these magical things called enzymes. In other words, Kit Kat wafers and sperm everywhere. Once it is broken down, it is absorbed by the intestines and enters the blood.

So, what happens after fat enters the blood?

After absorption, the building blocks are converted back into fats or TAGs and carried in the blood.

Disclaimer: Fat is well, fatty. So it doesn’t mix well in the blood. It requires little transport vehicles called lipoproteins to help it mix and travel in the blood. Sort of a like a visa. Without it, you cannot travel. As an immigrant perhaps that’s why lipoproteins remind me so much of home.

A underappreciated chylomicron trying to impress Optimus Prime

Anyway, when fats are absorbed by the intestines, they are carried in the blood as little droplets containing mainly TAGs as well as cholesterol and phospholipids by lipoproteins called chylomicrons. Chylomicrons are better known as the little minion Transformers that don’t make the official cast but, instead help to bring water in between scenes and organise the snack table for the likes of Optimus Prime and Bumblebee.

These chylomicrons deliver fats to cells within the body. As the fats enter the cells, it is once again broken down into its fatty acid and glycerol building blocks. One of two things can happen; either they are used (e.g. for energy or other uses such as forming cell membranes, absorbing nutrients, forming hormones) or they are resynthesized and stored as TAGs.

So, where are fats stored and why?

Fat is stored mainly in 2 places: adipose (fat) tissue or the liver. Its major function is as a source of energy but, it also functions as insulation to keep you warm.

Remember, it is not only fat that gets stored as TAGs. Excess glucose is also converted and stored as TAGs. This happens for two reasons. Firstly, you can only store limited amounts of glycogen. In fact, whilst you can only store a few hundred grams of glycogen in the body, you can store kilograms and kilograms worth of fat (as you may have noticed). Secondly, fat is a super-efficient way to store energy. For the same weight of glucose, fat can hold more than twice the calories. This is discussed in more detail in my previous post “What Causes Obesity Part 3: Eating Carbohydrates.”

So, how do we breakdown our fats to make energy?

When fats are needed for energy, it’s time to go into breakdown mode. Adipose or fat tissue is made up of almost pure TAG. The TAG stores are broken down into fatty acids and glycerol and transported in the blood to cells that need the energy.

When do fats become the preferred energy source over carbohydrates?

Generally speaking, carbohydrates or in particular glucose, represent the preferred energy source. Fat becomes preferred when cells have little access to glucose. When would this happen?

It falls loosely into two main categories.

1) Not eating enough carbohydrates e.g. starvation, fasting, strict “no carb” or “high fat, high protein” diets.

2) There is glucose in the blood but the cells can’t access it because they don’t have enough insulin e.g. untreated Type 1 Diabetes

A quick word on the buzz word “ketosis”

At the same time that fatty acids are used as an energy source in times of low glucose availability (whatever the cause), the liver converts fatty acids into glucose in a process called gluconeogenesis. This is discussed in more detail in my carbohydrate post. A by-product of this process are ketone bodies or keto-acids. Hence why some low carb and high fat diets are called “ketogenic diets”.

Ketone bodies are actually a useful source of energy. The problem arises when the rate at which it is produced outweighs the rate at which is used. If it builds up, it makes the blood more acidic and this is not good! Everything in the body, including the pH of the blood and cells, is kept in a fine balance like the flavours in a chicken curry. Any changes affect how everything works and you can even potentially die!

Fun (not so fun) fact: Many type 1 diabetics find out they are diabetic when they become super sick from a severe case of ketoacidosis.


Summary of what happens to fats after you eat them

















The Cause Of Obesity: Part 1

The Cause Of Obesity: Part 2 Changing Bad Habits

The Cause of Obesity Part 3: Eating Carbohydrates

Weight Loss Solutions: Sustainability 

The whole (food) does not equal the sum of its parts

As always, stay in school, don’t do drugs and I will give you 1000 rupees if you name your next born child Chylomicron.

Thank you for reading and if you got any value from this, please share. If you would like to comment on this post or anything obesity related, I would love to hear it!

Dr G