Insulin – the basics (it's a complex hormone)


Insulin is a major player in how we use energy sources and so in turn a major player in obesity and chronic illness. It does lots of other things too.

Much written about as an anabolic hormone, it is probably actually anti catabolic ie it stops the breaking down of things – e.g glycogen to glucose, protein to amino acids, stored fat to fatty acids.

It is made by beta-cells in the pancreas.

High blood sugar causes the release of insulin. However we can think of insulin and its roles in a sort of ‘dose’ framework. By the time insulin is moving sugar out of the blood and into cells to be stored, the amount of insulin required to do this is relatively quite high. Before we even get to this, insulin is:

  1. Suppressing glucagon at the level of the alpha cells in the pancreas.*
  2. Suppressing gluconeogenesis at the liver (and stimulating lipogenesis).**
  3. THEN it acts further in the periphery doing other stuff like stimulating uptake of glucose in to muscle and liver cells and fat into fat cells.

Carbohydrates are the main dietary cause of a quick increase in blood sugar and therefore insulin release. The biggest release is likely to come from a combination of refined carbohydrate and refined fats – aka junk food, processed food.

*Glucagon essentially does the opposite to insulin, click on the link for more.

** Gluconeogenesis is the production of glucose in the liver. Lipogenesis is ‘making fat’.

Eating protein also causes insulin to rise but doesn’t have the same impact on our blood sugar.  Protein ingestion results in a comparable rise in glucagon, reducing the insulin to glucagon ratio which is the important thing. Glucagon does the opposite to what insulin dose.

Eating fat on its own causes minimal increases in insulin and no increase in blood sugar. But if we have too much energy substrate around, more than we can store properly , the fat cells require higher levels of insulin to try and keep the fat locked up where it is – see

So, insulin levels change in varying degrees depending on what we eat and its actions are different at different amounts.

Insulin moves glucose (sugar) from the bloodstream into tissues that need them for energy primarily your liver and muscles to be stored for use. Glucose is stored in these two places as something called glycogen. You can store about 100g of glycogen in your liver and about 300g in your muscles. The uptake of glucose into the muscles doesn’t always require insulin, there are insulin independent means of getting glucose into your muscles. Zone 2 exercise is a great way to optimise the receptors that allow for this.

If these two places are full, we send the glucose to be changed into something called a triglyceride (a type of fat) and to be stored in your fat cells – subcutaneous adipose tissue (under your skin). If this gets too full it is then sent to ectopic fat stores (around your organs, in your muscles, around your heart.

So insulin sends the glucose in your blood to either a tissue that can use it for energy or to your storage depot for later use. 

We need our circulating insulin levels to be generally low, but effective. A spike in relation to food is normal, but we want that spike to be small and short lived. In other words we don’t want a lot of insulin floating around in our blood constantly (this is known as hyperinsulinaemia).

Eating frequently through the day, especially eating frequent high refined carbohydrate, carb and fat combinations, processed foods results can result in hyperinsulinaemia. These types of hyperpalatable foods can make it hard to stop eating, they activate dopamine receptors making us feel good, the cause swings in blood sugars resulting in lots of hunger and they switch off satiety centres so we just don’t feel full. The result is excess energy that we don’t need and have to find storage for . ‘Keeping intake to levels that support exercise but not body fat’ is incredibly difficult on a highly processed diet that’s full of both refined carbs and refined fats, it has very little to do with will power….

It is beneficial for us to have very efficient insulin! At the end of our lives – the least amount of insulin we’ve needed, probably the better.

Insulin is also a trigger for lots of other processes and sets off lots of different cascades . It’s important! It has a major role. We want it to be working efficiently and be around when we need it. Not all the time.