What Insulin Actually Does, In Plain English

You have heard the word a hundred times. Insulin. It comes up in every article about energy, weight and cravings, usually with no explanation at all.

So here is the explanation. No biology degree needed. It takes about five minutes, and once you have it, most of the advice on this site will make more sense.

1. Glucose is the fuel

When you eat bread, rice, fruit, potatoes or anything sweet, your body breaks it down into a simple sugar called glucose.

Glucose is the fuel your cells run on. Your brain uses a lot of it. So do your muscles.

After a meal, glucose passes from your gut into your blood. That is what “blood sugar” means. It is simply how much glucose is in your blood at that moment.

Blood sugar going up after a meal is normal. It is supposed to happen. The question is how high it goes, how fast, and how long it takes to come back down.

2. Insulin is the key

Here is the part most people never hear. Glucose in your blood cannot get into your cells on its own. It needs help.

That help is insulin, a hormone made by your pancreas, which sits just behind your stomach.

When your blood sugar rises, your pancreas notices and releases insulin. Insulin travels through the blood and works like a key. It lets glucose into your cells, where it can be used for energy or stored for later.

As the glucose moves out of your blood and into your cells, your blood sugar comes back down. Then the pancreas eases off.

That is the whole system. Glucose is the fuel. Insulin opens the door.

Insulin has one more job worth knowing about. While it is high, it also tells the body to store energy and not to burn what is already stored. That is useful after a meal. It is less useful when insulin stays high for most of the day. Then the body spends most of the day in storing mode, and that is one reason weight gets harder to move. It is also why grazing all day can work against you, even when each snack is small.

3. A picture that helps

Think of your cells as a car park, and glucose as the cars.

Insulin is the team of attendants. When the cars arrive, the attendants wave them into empty spaces. Everything moves. Nobody waits long at the entrance.

Now picture a very busy day. Cars keep arriving, all at once, over and over. The car park is filling up. The attendants have to work harder to find spaces. The queue at the entrance starts to grow.

So the car park hires more attendants. For a while, that works. But more attendants do not make more spaces. If the cars keep coming and the car park stays full, the queue keeps growing, no matter how many people are waving.

That queue is blood sugar that stays high for longer than it should.

4. When the key stops turning easily

Over time, if the car park is often full and the attendants are often shouting, the cells start to respond less to insulin. The key still fits, but it turns less easily.

The pancreas answers by making more insulin. For a long time, sometimes years, that keeps blood sugar looking normal. But it takes more and more insulin to do the same job.

This happens slowly, and for a long time you feel nothing specific. What you might notice is being hungry soon after eating, a big energy slump in the afternoon, and weight that settles around the middle. Those are all things this site talks about a lot. This is the reason why.

5. Why it gets harder after forty

Two things change for most women in their forties.

Muscle goes down. Muscle is the biggest car park in the body. It is where most of the glucose from a meal is stored. Less muscle means fewer spaces.

Estrogen falls. Estrogen helps cells respond well to insulin. As it drops through the perimenopause, the key turns a little less easily, even if nothing else has changed.

So the same breakfast you ate at thirty lands differently at forty-five. That is not you doing anything wrong. It is the car park getting smaller while the cars stay the same.

6. What helps, and why

Everything that follows works on one side of the picture or the other.

Slow the cars down. Eat protein and vegetables first, and starch last. Choose food with more fibre. Pair fruit with yoghurt or nuts. All of these make the glucose arrive in a steady stream instead of a rush.

Build a bigger car park. Strength work, twice a week. More muscle means more places for glucose to go, at every meal, for the rest of your life.

Use a side entrance. Working muscles can pull glucose in without needing much insulin at all. That is why a ten-minute walk after a meal works so well. It opens a second door, right when the cars are arriving.

Give the attendants a break. A decent overnight gap between dinner and breakfast, and good sleep, give the system time with no new cars coming in.

None of these ask you to give up whole foods. They change how and when the fuel arrives, and how much room there is to put it.

7. What an ordinary day looks like to your car park

It helps to walk through a normal day with the picture in your head.

At seven you have toast and jam and a sweet coffee. Almost all fast fuel, with nothing to slow it. The cars arrive in a rush, the attendants scramble, and by half past nine the lot has emptied out too fast. That empty feeling is hunger, and it comes with a biscuit.

At one you have a sandwich at your desk and do not move for three hours. The cars arrive again, and this time there is no side entrance open, because your muscles are sitting still.

At four you feel flat, so you reach for something sweet. More cars, arriving on their own.

Now run the same day again with small changes. Eggs and toast at seven, so the cars arrive in a steady line. The same sandwich at one, followed by a ten-minute walk to open the side entrance. A handful of nuts at four instead of the biscuit. Same amount of food, more or less. A very different day for the attendants.

That is what this whole site is really about. Not eating less. Changing how the fuel arrives.

What this does not mean

It does not mean glucose is bad, or carbs are bad. Glucose is your fuel, and you need it.

It does not mean you can tell from how you feel what is happening in your blood. If you are worried, a simple blood test at your doctor’s is the only way to know, and it is worth asking for.

Start with one

Of the four ideas above, pick the easiest one for you this week.

For most people, that is the walk. Ten minutes, straight after your biggest meal of the day. Around the block, up and down the stairs, or a lap of the garden.

Do it for a week. Notice how you feel an hour after that meal. Then think about the next one.

This is general information about food and daily habits, not medical advice. Talk to your doctor before changing anything, especially if you take medication.