Lessons in fat

It dawned on me the other day that I have named myself the fat doctor, but I am write a blog post about fat. Epic fail!

So today I am going to rectify that and try and explain the science behind fat. I’m also going to challenge some of the common myths that I hear from patients time and time again, whenever I broach the subject of weight gain.

And before anyone asks, yes this is going to be another one of those science-y type posts. And no, I make no apologies for it.

Lessons in fat number 1: Where does fat come from?

Well that’s obvious. It comes from your diet, right?

Actually, not necessarily.

Myth number one: A high fat diet is the number one cause of obesity.

To understand the science behind fat, you first have to go back to basics. Lets start with eating (my favourite part of the process). First the food needs to break down into small molecules (a process we call digestion). Then it travels through the blood and is used up by the body.

Most people know that everything we eat is made up of three main macronutrients – carbohydrates, proteins and fat. Carbohydrates break down into sugar molecules. Sugar (or glucose) is the main source of energy for all living cells.  Without it, our body cannot function.

[The problem is that most of us eat too much of it. But I’m getting ahead of myself.]

Back to digestion. It actually starts the moment food enters our mouth, when an enzyme called amylase starts to break down the carbohydrates. Once the food reaches the stomach, proteins start to break down.  By the time food reaches the small intestine, the body begins to digest fat.

As you can see, carbohydrates start breaking down first, then protein, then fat. That explains why foods that are high in fat and protein make us feel fuller for longer.

Lessons in fat number 2: Insulin and fat

You have probably heard of insulin but you may not know what it actually does. Don’t worry, I still struggle to get my head round it and I actually prescribe it to my patients on a regular basis!

When we start eating, the pancreas releases a hormone called insulin.  I like to think of insulin as a key that fits inside a lock. The lock opens the door of the cells, and lets the sugar in.

Once inside, the sugar can do one of two things. It either gets turned into energy or it gets stored as fat. See where I am going with this? We don’t need to eat fat to feed our fat cells. We can make fat from sugar.

Myth number two: diabetics can not produce insulin.

Whilst type I diabetics do not produce any insulin of their own, the majority of people with diabetes are Type II and they are still able to make insulin.  The problem is that their cells have become resistant to it.  High levels of insulin in the blood over time leads to insulin resistance. This is why diabetes is linked to obesity.

Lessons in fat number 3: Lipogenesis

So, lets recap. First, food is broken down and absorbed. Then it travels through the blood and gets absorbed in to cells. Any excess sugar that is not used by our cells gets turned into fat

The technical term is Lipogenesis, and it literally means “creation of fat”. The more unhealthy your diet, the better you become at turning sugar in to fat. It becomes your body’s superpower and before you know it, your waistline starts expanding!

So whilst a lot of people are under the impression that we get fat by eating too much fat in our diet, it is perfectly possible to gain weight on a low fat diet. Why? Because we still eat too many carbohydrates.  Especially simple carbohydrates such as sugary food and drinks.

Lessons in fat number 4: Glycaemic Index (GI)

You may have heard of the GI index.  This rates food in terms of how quickly they raise our blood sugar.  Pure sugar scores 100. The higher the score, the quicker your blood sugar rises. 

As I said already, spikes in sugar levels are dangerous for a couple of important reasons.  Firstly, we turn the sugar into fat and we start to gain weight.  Secondly, the body has to produce lots more insulin in response, and this leads to insulin resistance which in turn leads to type II diabetes.

Low GI foods, on the other hand, are absorbed at a much slower rate.  Examples of low GI foods include vegetables, wholegrains and pulses.  Foods high in protein and fat also have a very low glycaemic index.  

Myth number three: low GI foods are good for you

On the whole, we should be choosing low GI foods over high ones. But beware – many low GI foods still contain a lot of calories. It all depends on the portion size. If you want to know more about the GI index, check out the information on the Diabetes UK website.

Lessons in fat number 5: Gluconeogenesis

This all sounds very depressing, but the good thing about the science of fat is that it works both ways. If you consume less energy than you need to each day, your body will need to find a way to make more energy.  So what does it do? It breaks down fat and protein, and turns them in to sugar.

This process is called gluconeogenesis.  It literally means “creation of glucose”.  Note that I said fat and protein.   Most of us are desperate to lose fat but understandably want to keep the muscle.

Myth number four: all weight loss is good

The problem is that when we start eating less and exercising more and begin to lose weight, only 75% of it is fat. The rest is lean (muscle) mass. And that can be dangerous for a number of reasons. Getting rid of visceral abdominal fat has a whole host of benefits, but going the other way and losing too much weight leads to muscle wasting. And that is never a good thing.

There are ways around this, but some degree of muscle loss is unavoidable.

Lessons in fat number 6: Energy deficit 

To sum it all up, sugar is the main source of energy for our cells.  If we eat more than we need to, our body turns sugar in to fat.  If we eat less food than we need, our body turns our fat stores into sugar. 

Foods that cause spikes in our blood sugar will not only increase our fat stores, but they will lead to excessive insulin production which increases our risk of diabetes

I am a big believer in ditching the diets. Whilst I believe that most weight loss programs have their merits and have been shown to be effective in the short term, I think they all have their downsides as well. And I don’t think there is any real evidence that they benefit most people in the long term.

I’d much rather promote the benefits of eating a healthy diet. If we understand the science behind fat, I think we can make healthy choices on our own, without the need to follow a prescribed set of rules. It’s like buying shoes – you’ve got to find the the pair that fits your feet.

Photo by Alexandra Maria

We just need to use a bit of common sense. We clearly need to limit the amount of high fat, sugary foods that we eat. That goes without saying. Fat is not necessarily bad for you, but it is highly calorific so we also need to limit the amount you eat.

Carbohydrates are not the villains of the macronutrient world that they are often portrayed as nowadays. But they are not necessarily the healthy option either. Lean protein is a good choice but man does not live by meat alone (unless you’re doing keto, in which case…)

The main thing to remember is that our body is able to turn energy into fat, and it is also able to turn fat in to energy. So why not join me and #ditchthediet and #eathealthyfood instead?

Got any questions or comments about the Fatdoctor’s mini science lesson? Then why not leave a comment below. If you want to find out more about me or subscribe to my website, then click here.

2 thoughts on “Lessons in fat”

  1. Pingback: How fat saved my family - The Fat Doctor

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