Fat Trucks are an easy way to help illustrate the complex but fascinating world of fat metabolism.

Every animal cell contains cholesterol. Every animal cell makes cholesterol. The liver, which makes the majority, regulates and maintains our cholesterol levels.

Yet, after more than 2,000,000 years of evolution, many of us are being told that our levels of cholesterol are too high. And that we need to take medications called statins daily for the rest of our lives. It has even been suggested that statins should be added to our drinking water.

As a retired GP with 40 years of experience, I am well aware that there are problems with the way we metabolise fat.

Cholesterol and Atheroma

Levels of obesity and type 2 diabetes are rising rapidly. Atheroma is the proper name for hardening and blocking of the arteries. It contains cholesterol and is the leading cause of heart attacks and strokes.

There is a link between cholesterol and atheroma, but that doesn’t make cholesterol the cause. It is important, when reading scientific literature, to recognise that correlation and cause are not the same.

Fat metabolism is a complicated and difficult process. But there is a real need in the community to understand it better.

What follows is my attempt to take some serious science and make it more understandable. Based on solid science, with some lighter moments to make it more easily understood. I hope it expands your understanding of this complex and important subject.

Fat Metabolism – Is there a difference between fats?

I’ve recently refined my thoughts on questions that have exercised my mind for some time. Is there a difference between the fat we eat and the fat found in and around the liver? We think of them as one substance, but are they? Why should fat from such widely different sources be the same? Might they have different functions? And does eating fat make us fat?

Let’s look at some of the differences

The fat we eat is absorbed through the small bowel and has many day-to-day functions throughout the body. The fat around the liver is a long term energy store for times when food is scarce. It is converted by the liver from excess carbohydrate in our diet.

It is well known that a high grain (carbohydrate) diet fattens the livers of geese and ducks. Check out how to make pate de fois gras. (Warning, this video may cause distress to some viewers.)

It is also well known that a high alcohol diet leads to fatty liver disease and a ‘beer gut’.

But does eating fat makes us fat?

There is plenty of evidence that it does not.

A high fat, low carbohydrate diet reduces abdominal obesity. This is compared with the same calorie intake from a low fat, high carbohydrate diet.

Carbohydrate makes us fat but dietary fat does not.

Dr. John Beaney

As we know, fat is stored in many other parts of the body apart from around the liver. The majority of this fat consists of triglycerides.

A slim 68 kilogram male would have about 7 kilogram of fat. Only a tiny proportion of this fat is cholesterol; according to Wikipedia, about 35g, contained mostly within the cell membranes.

There is one fat that can help us distinguish between dietary fat and fat found in and around the liver. It’s called palmitoleic acid. There is very little of this fat in our diet unless we eat lots of avocados and macadamias.

In the absence of these foods, large amounts of it can still be found stored around the body. It is produced by the liver from carbohydrates as described by Jeff Volek and Stephen Phinney in ‘The Art and Science of Low Carbohydrate Living‘.

It is the chronic overconsumption of carbohydrates that results in excessive fat production. This leads to visceral obesity, metabolic syndrome, and atheroma.

Dr John Beaney

We are also good at making cholesterol

Cholesterol is a fatty substance, found in every cell membrane and manufactured in virtually every cell in the animal kingdom. It is an essential component of many hormones. Cholesterol provides a protective sheath for nerve cells and is converted into vitamin D by sunlight. The list goes on and on.

There are sophisticated mechanisms for maintaining stable blood levels of cholesterol in the body irrespective of the amount ingested.

Cholesterol is an essential substance, not one to be avoided.

Because cholesterol is found at the site of atheroma it is assumed to be the cause of atheroma.

For 50 years we have been encouraged to limit our consumption of fat in general and cholesterol in particular. It is timely to review this hypothesis.

Nowadays, some prefer to regard the presence of cholesterol in arteries hardened with atheroma as akin to ambulance officers at the scene of a road accident. Just because they are at the accident, it doesn’t mean they caused it.

This is not a bad analogy. But if we change the ambulance for a truck loaded with fat, we can develop the idea to a more logical conclusion.

Understanding Fat Trucks

fat truck

To illustrate, let’s imagine there are two trucking companies that move fat around the body in the blood. One has the sole contract for the fats we eat and is based in the small bowel. Just for fun, let’s call that company ‘GoodFats’.

GoodFats doesn’t own the trucks. It just provides drivers and ensures that the fats absorbed in the small bowel get to their correct destination.

The other trucking company; let’s call that one Livermore’s. It has the sole contract for distributing fat manufactured in the liver – two different organisations to run very different operations.

Good Fats Fat Truck Driver

We’ll start by looking at the GoodFats bowel contract. I’ll tell you about Livermore’s and the liver contract further down.

Blood is water-based. And, because fats don’t dissolve in water, the trucks used for carrying fats in the blood are carefully designed.

All fat carrying trucks have the brand name ‘lipoprotein’. But the truck model exclusive to the bowel and used by GoodFats is called a chylomicron. The chylomicron truck is made in the cell wall of the small bowel and loaded with fat. It is then ready to start its unique journey.

The two main fats, triglycerides and cholesterol, are packed inside the lipoprotein truck. The outer shell, made of phospholipid, enables the fat to exist in water.

Special proteins called apolipoproteins are embedded in the outer shell. We are interested in one of them, called ApoB.

Stay with me – this is exciting….

The two other main foods, proteins and carbohydrates, diffuse straight into the blood from the bowel. They don’t need special trucks. However, before they can enter the general blood stream, they are whisked off to the liver in a special blood vessel. This is where they go through something akin to customs, immigration, and quarantine.

Meanwhile, the GoodFats chylomicron trucks loaded with fat from the bowel start an entirely different journey.

In addition to the blood there is another fluid system in the body called the lymphatics. The lymphatics starts at the periphery of the body. The hands, feet, and bone marrow and returns lymph to a large vein in the neck. Because of this process, the lymph and its contents avoid the liver entirely.

The lymphatic system carries many different sorts of cells. eg: cells from bone marrow, lymphocytes, antibodies, macrophages, and T cells from the spleen and thymus glands. The lymph then passes through nodes where unwanted intruders become blocked.

An infected toe may result in an enlarged lymph node in the groin, full of cells that destroy the germs. The nodes also contain and eliminate cancer cells.

My best guess is that the lymphatic system eliminates millions of cancer cells. Only occasionally will cancer overwhelm the system’s defences to become a cancer metastasis.

Immunity, infection, and cancer control are major roles for the lymphatic system but, as if that wasn’t enough, it has one more function. As the lymphatic system passes the intestines it takes on board all the GoodFats trucks. Laden with fat, it sweeps them up into the vein in the neck.

Unlike the carbohydrates and proteins, the antibodies and immune cells together with the fats entirely avoid customs, immigration and quarantine in the liver.

This is no accident.

Clearly, there must be developmental advantages for dietary fat to be treated in such a special way.

Back to the GoodFats Fat Truck driver…

fat truck

We left our GoodFats driver travelling in the lymphatic system with his chylomicron truck loaded with the fat we’d recently eaten. The driver hangs a right and finds himself in the blood stream. In an instant he is through the right atrium of the heart and a second later, in the lungs.

Feeling as though he’s on a roller coaster, he quickly finds himself back in the heart. Then, it’s onto the main arterial highway, the aorta. From there, he sets course looking for cells requiring his cargo of fat.

Remember ApoB, a single molecule found in the wall of each lipoprotein truck?

The chylomicron truck has a unique version of ApoB called ApoB48. Our driver is looking for customers with receptors matching ApoB48 to offload the fat contents of his truck.

His customer is likely to be a muscle cell because muscles use a lot of fat. But it could be, for example, a gland requiring cholesterol to make a hormone. The skin on a sunny day turning cholesterol into vitamin D or just about any other cell in the body.

GoodFats is very efficient. The chylomicron trucks containing the great majority of the fat we eat – triglycerides – reach their destination speedily. Typically, a few hours after a fatty meal, the triglyceride level in the blood is significantly lower than levels found after a high sugar/carbohydrate meal.

This is interesting – not what we have been led to expect.

GoodFats delivers the now-empty truck (called a chylomicron remnant) to the liver. Here, it is broken down and the parts sent back to the bowel to be assembled into a brand new chylomicron truck. The process begins again.

Animal metabolism has changed only marginally in millions of years. To see how our processes compare with a very distant cousin, I checked out the duck-billed platypus, an egg-laying mammal. Its lymphatic system drains the bowel in a way virtually identical to ours. The more I study the workings of the human body, the more fascinated I become!

What about Fatty Acids in the Liver?

We now turn our attention to the liver. Along with many other functions, the liver manufactures cholesterol and fatty acids.

I’m calling the trucking company with the sole contract for distributing liver fat ‘Livermore’s’. The liver provides Livermore’s with a variety of fat truck models to transfer fat around the body.

They all belong to the same ‘lipoprotein’ brand as did the chylomicron truck. But here the models are called VLDL, IDL, LDL and a small truck called HDL which is used to return cholesterol to the liver.

GoodFats fat trucks had that special protein – ApoB48 – to help the driver find a suitable customer. The Livermore’s fat trucks have a different protein – ApoB100.

Different trucks for different customers

As we have just heard, the fat we eat is diverted away from the liver, straight into the general circulation. The fat found in the liver is manufactured in the liver. Sources include glucose excess to our energy requirements, dietary fructose, and alcohol.

Alcohol is not strictly a carbohydrate. However, it comes from fermented sugar and the liver treats fructose and alcohol in similar ways. The body has no way of storing excess protein so that is converted into glucose too.

The glucose in the liver comes from sugar but also from complex carbohydrates. This includes grain-based products such as bread, pasta, etc. as well as rice and many root vegetables, such as potatoes.

In Australia, most fructose comes from cane sugar, honey, and fruit. In the USA and in some other countries, high fructose corn syrup is an important source.

Beware the hidden sugars

Sugar is included in all manner of manufactured food. Be aware, you may be eating far more sugar than you realise.

If you take fruit and alcohol at roughly the same time as you eat carbohydrate, you can be pretty sure that the vast majority of the fructose and alcohol will be converted into fat in the liver along with glucose surplus to energy requirements.

Once the excess sugar/carbohydrate has been converted into fat in the liver, it needs to be stored somewhere.

Where is the fat stored?

It’s best to think of the fat being stored in three distinct areas:

  • in the liver
  • around the liver
  • elsewhere around the body – mostly just under the skin – subcutaneous fat.

Fat stored in the liver made from too much alcohol is called alcoholic fatty liver disease (how’s that for imagination?). Commonly shortened to AFLD.

The fat stored in the liver from excess sugar is called non-alcoholic fatty liver disease or NAFLD. Droplets of fat appear spontaneously in the liver and don’t need delivery trucks.

Fat stored around the liver is worthy of our particular attention. Because it is very likely to be related to metabolic problems. In some people, it can amount to a lot of fat.

What is TOFI?

Sometimes we are ‘Thin on the Outside but Fat on the Inside’. That’s known as TOFI, and that’s also a concern for the same reason.  Livermore’s delivers to fat stores all-round the body. 

So, GoodFats and the bowel contract bypasses the liver. It delivers dietary fat for day to day needs, while Livermore’s liver contract is intended for storage. To be used when fresh food is scarce. We still see this working successfully with many wild animals.

But many of us now have access to a constant surplus of sugar and or carbohydrates throughout the year. Over time, this can result in us getting very fat.

How does the fat leave the liver?

Back to the liver where Livermore’s are doing a great job. With large amounts of excess sugar being converted to fat, fat-laden trucks leave the liver. Each with an APoB100 molecule looking for a customer with a matching receptor.

With a liver overflowing with fat, there are more fat-laden trucks leaving the liver than there are customers wanting fat. The cells around the body that store fat will take it all eventually. But they can only store so much in one day. This leaves the trucks driving around looking for customers for too long.

Night time comes and the Livermore’s truck, still full of fat, is parked in a roadside truck park. The driver is unaware of an approaching vandal. The vandal is sugar.

The excess fat was caused by excess sugar. So, it’s no surprise that sugar is also in the bloodstream in excess quantities. We know this condition as prediabetes, type 2 diabetes or metabolic syndrome.

Excess sugar vandalises many tissues in the body. This process is called ‘glycation’. Vandalised tissues in the eye cause diabetic retinopathy, in the kidneys diabetic nephropathy and in the nerves, diabetic peripheral neuropathy. There is evidence of sugar vandalism for years before we recognise the condition as type 2 diabetes.

Small dense LDL

Sugar damages the ApoB100 protein.  After it is damaged the LDL becomes a little smaller and is then known as small dense LDL (SDLDL).

The next morning the Livermore’s truck driver sets off to look for a customer. But, with a vandalised ApoB100, customers don’t recognise him and won’t accept the load of fat he is carrying.

He returns to the liver hoping to offload there. The liver also refuses to accept the return of a vandalised truck. The SDLDL truck keeps travelling and sugar vandalism continues.

The only way an SDLDL can be taken out of service is by a burly refuse disposal merchant called a macrophage. He’s a form of white cell that can literally swallow an SDLDL whole.

Macrophages circulate in the blood. They also move inside small tears in the walls of the arteries where they busily try to heal the tear. 

Over many years, macrophages loaded with SDLDL (and now called foam cells) can accumulate inside blood vessels with chronic tears in their wall.

And this is where the real danger lies.

Arteries begin to harden

Foam cells gather together over the years (it can take 40 years) and you develop hardening of the arteries. This is known as atheroma.

As the mass of foam cells and debris grow they may block the artery. Or a piece of atheroma can break off and travel in the blood until it blocks a smaller vessel. If the artery is in the heart, we call it a heart attack; if it’s in the brain, we call it a stroke.

It’s really coincidental that the SDLDL contains fat and cholesterol.  The cholesterol was just a passenger in the LDL truck when it got stuck in the blood vessel inside the macrophage.  

The take home message is clear

The problems associated with our modern diet are not caused primarily by fat but by sugar. These problems include; obesity, type 2 diabetes, high blood pressure, and disorders of fat metabolism, together known as the metabolic syndrome,

It is not excess fat in our diet or too much cholesterol that are causing these problems. Rather, it’s too much sugar, fructose, and other forms of carbohydrate.

There’s nothing wrong with fat

Referring to HDL as ‘good’ and LDL as ‘bad’ is meaningless. They are just HDL and LDL. Successfully trucking fat around the body for millions of years, throughout the whole animal kingdom. That is, until the LDL was vandalised (glycated) by excess amounts of sugar.

Reduce the amount of sugar in the diet and there will be less sugar being converted into fat.

The problem of obesity and type 2 diabetes in the community requires urgent attention. 

The problem with Statins

The Fat Truck story would not be complete without some reference to the cholesterol-lowering group of drugs known as statins.

Cholesterol has been an essential component in every cell and every mitochondrion, in every member of the animal kingdom, for in excess of 500 million years.

50 years ago scientists decided that excess cholesterol was responsible for atheroma and therefore heart attacks and strokes. They set about finding a drug to reduce cholesterol levels. The result was, among others, statins.

Statins are a class of drugs introduced in the 80s to reduce the amount of cholesterol manufactured in the liver. The liver enzyme HMG-CoA reductase plays a central role in the production of cholesterol and statins block its action. 

They are effective and statins have been successful from a sales point of view: about $29 billion annually.

Statins certainly work

They lower levels of cholesterol and LDL, both considered ‘bad’.  Unfortunately, they also reduce HDL which is described as ‘good’.  The companies like to ignore the HDL effect.  I use inverted commas because I strongly dispute these descriptions.

In their defence, statins have been shown to have anti-inflammatory properties. Albeit weak properties, quite separate from their role inhibiting statin production.

But what if this concept is all based on a false premise?

  • What if the cholesterol hypothesis is wrong? What if 500 million years of successful evolution trumps 30 years of poorly conceived science?
  • And what if a high sugar diet is responsible for excess fat production?
  • What if high levels of blood sugar damage LDL and lead to atheroma?
  • And, finally, what if excess sugar is strongly inflammatory and reducing dietary sugar is strongly anti-inflammatory?

There are many who believe that the time has come for a major re-evaluation of the role of cholesterol-lowering drugs.

500 million years of evolution does indeed trump 50 years of bad science.

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