What to know about insulin and body composition

Good morning.

When carbohydrate is consumed, it travels through the digestive system, is broken down to glucose (sugar), and enters the bloodstream causing blood glucose (blood sugar) to rise.

The body likes to keep blood glucose within a narrow range, to ensure there is enough to be used for energy but without overloading things.

So when the blood sugar rises it exceeds this range, the body decreases it by shifting glucose into cells or tissue (ie. muscle).

However, glucose can’t just go into cells - it needs the door to be opened for it.

This is where insulin comes in. 

Insulin mediates the entry of glucose into the cell - it attaches to the cell receptor and allows glucose into the cell.

Some people call it the Lock And Key Model.

From uni, we deduced the Nightclub Model, whereby the cell is a nightclub and guys (glucose) cannot get past the bouncer (cell receptor) without some female friends (insulin).

Insulin also increases uptake of fatty acids, although the process is not exactly the same.

But this doesn’t mean that insulin makes you fat.

It’s more so that if you are storing glucose, you aren’t going to be mobilising fatty acids. Just like if you are making a $500 deposit at the bank, you aren’t going to walk out and grab $400 from the ATM.

Insulin’s job is to just move glucose into the cell. It doesn’t have an agenda to increase body fat, it just has a job to do.

If you eat too much food, then more glucose will be stored. Firstly in the muscle, but if that’s full (due to lack of exercise) it will be converted to fat.

Again, insulin isn’t trying to do this - the body’s carb stores are just filled and this is the other option.

But what about insulin resistance?

Insulin resistance is associated with chronically elevated blood insulin and blood glucose levels, because insulin can no longer do its job.

Because there is chronically high blood glucose, and therefore blood insulin levels, the cell receptors become less sensitive to insulin.

This means that the insulin in the bloodstream can no longer do its job, meaning blood glucose stays higher.

The problem is that because blood glucose is high, more insulin is secreted, as the body just sees high blood glucose and this is the solution.

This doesn’t fix the problem.

To go back to the Nightclub Model, there are now tonnes of women inside the club - so the bouncers won’t guys you in anymore, no matter how many ladies are with you.

This means all the guys are caught outside on the street, of which the consequences are not dissimilar to chronically elevated blood glucose. 

Lower carbohydrate diets can be beneficial for managing blood glucose during a weight loss phase, particularly if insulin sensitivity is a diagnosed issue.

However, unless an energy deficit is created - there is no stimulus for weight loss.

Exercise increases insulin sensitivity because the muscles want to be ready to take up energy for activity.

If someone is preaching a low-carb diet based on science, I recommend asking these two questions:

Can they explain why it’s beneficial?

Is that the best way for you to create an energy deficit?

If they can’t explain it, they don’t understand it.

And if it’s not the best way for you to create a deficit, don’t do it!

Tom Fitzgerald