How does insulin work

Fact-checked by Dr. Anthony Gustin, DC, MS.

Written by Brian Stanton

Most people think of insulin as diabetes medicine. When someone has type 1 diabetes, they need regular insulin treatments to stay functional. You probably knew that already.

But insulin is much more than an injection. Inside every human on the planet, the hormone insulin regulates blood sugar, promotes muscle growth and even prevents damage to brain cells and blood vessels.

So how does insulin work? What happens when insulin doesn’t work? And how can you get this hormone working for you?

I will answer all those questions in today’s guide:

But first, let’s define insulin.

What Is Insulin?

Insulin is a hormone — a chemical messenger that delivers messages to your cells. These messengers regulate nearly every function in your body, from growth to immunity to appetite. Without hormones, you wouldn’t last long.

Fortunately, glands within your body are constantly releasing hormones. Your glands are always listening, and when one or more stimuli — food, light, exercise, stress, etc. —  is present, hormones are unleashed to deliver their messages.

A gland called the pancreas, which sits behind the stomach, is responsible for releasing the hormone insulin into your bloodstream. How does the pancreas know to release insulin? There are several triggers, but the main trigger is sugar, or glucose, in your blood.

Glucose in your blood comes from food you’ve digested. When you digest a meal — especially one high in carbohydrates[*] — your blood sugar, or blood glucose, rises.

Glucose is a form of energy for your body’s cells, but if it stays in the blood for too long, it can create a condition called hyperglycemia and create damage to blood vessels, neurons and other cells throughout your body.

In other words, that blood sugar needs to be handled. That’s where insulin comes in.  

How Insulin Regulates Blood Sugar

High blood glucose signals specialized cells in the pancreas — known as beta cells — to start pumping out insulin. Insulin’s job is to get that blood sugar out of your blood and into your muscle, fat and liver cells to be stored away for future energy.  

There are several steps required for insulin to deliver sugar inside a cell:

  • First, insulin binds to insulin receptors on the cell’s surface.
  • Next, once insulin is bound to these receptors, transporter molecules on the cell — called GLUT 4 transporters — become active.
  • These GLUT 4 transporters do the heavy lifting: they schlep sugar from outside the cell to inside the cell.
  • Finally, the cell converts this sugar into either glycogen or fat.[*]

Glycogen is your main storage form of glucose, and exists almost entirely in your muscle and liver cells. About 400 grams of glycogen can be stored in muscle tissue, with an additional 100 grams in the liver.[*] This glycogen gets released (and converted back to glucose) for energy when, for instance, you do a long bout of endurance exercise in a fasted state.

After glycogen, fat is the next most common way your body stores excess glucose. Under the direction of insulin, about 10% of your blood sugar gets stored away as triglycerides — a stable form of fat.[*]

That’s right, insulin is a fat-storage hormone. It’s a survival mechanism, allowing the well-fed hunter gatherer to store food energy for later. When mammoth meat and tubers were scarce, our ancestors relied on body fat — adipose tissue that formed thanks to insulin — to keep moving, breathing and hunting.

Insulin, however, sometimes doesn’t work as it should.

Insulin Sensitivity and Insulin Resistance

You just learned how insulin regulates blood sugar by shoving that sugar into cells.

Ideally, here’s how that process looks:

  • You eat a meal
  • Your blood sugar rises
  • Insulin shuttles that sugar into cells for storage
  • Your blood sugar falls again
  • Your pancreas stops secreting insulin.
  • As your insulin levels fall, you shift from fat-storage (high insulin) to fat-burning (low insulin) mode.

To prevent a state of constant fat accumulation, you need this process to run smoothly. And if you’re insulin sensitive — if your cells take proper direction from insulin — this process should run like a Swiss watch.

Unfortunately, your body doesn’t always run like a TAG Heuer. Remember those receptors that insulin binds to on the surface of the cell? Sometimes they stop listening to insulin, and the GLUT 4 transporters don’t get activated. Then blood sugar doesn’t make it inside the cell. Instead, that sugar stays in the blood.

This condition — when your cells are resistant, rather than sensitive, to the signaling effects of insulin — is called insulin resistance.

If you’re insulin resistant, your blood sugar stays chronically elevated because glucose isn’t getting stored in your cells. This state of high blood sugar causes the pancreas to release more insulin than it normally would.

But don’t blame the pancreas. The pancreas doesn’t know your cells are insulin resistant — it only knows to pump out insulin when blood sugar is high.

As more and more insulin is released, you eventually enter a state known as hyperinsulinemia — too much insulin. Too much insulin, as I mentioned earlier, keeps you in fat-storage mode. Not good for weight loss.

But weight gain is only part of the picture. Insulin resistance is closely linked to metabolic syndrome — a condition defined by high fasting blood glucose levels, high blood pressure and excessive abdominal fat. About 25% of the US may have metabolic syndrome, and it all stems from problems with insulin[*].

Insulin Resistance and Chronic Disease

Insulin resistance, and the resulting hyperglycemia and hyperinsulinemia, are risk factors for many chronic diseases, metabolic syndrome included. I’ll review the major ones, but before that, let’s cover type 1 diabetes mellitus.

Type 1 diabetics aren’t necessarily insulin resistant, they just can’t produce insulin. That’s why type 1 diabetics need regular insulin injections or an insulin pump to manage their diabetes.

With that cleared up, let’s move on to illnesses specifically linked to insulin resistance:

  • Type 2 diabetes. This disease is the metabolic climax of insulin resistance. Type 2 diabetics can’t regulate their blood sugar due to GLUT 4 transporter defects, so they stay in fat-storage mode. Obesity, metabolic impairments and increased mortality risk are the hallmarks of this condition[*].  
  • Gestational diabetes. More or less type 2 diabetes during pregnancy, gestational diabetes increases mortality risk for both mother and baby[*].
  • Cancer. In addition to regulating blood sugar, insulin also promotes cellular growth and repair. This is good for building muscle, but not so hot for preventing cancer. Because of this, scientists speculate that insulin resistance, and the resulting hyperinsulinemia, may increase cancer risk[*].
  • Heart disease. By keeping blood sugar at a normal range, insulin helps protect your blood vessels from the damaging effects of hyperglycemia. But in the case of insulin resistance, that protection falters. To bear this out: The Helsinki Policeman Study followed 970 men over 22 years and found that hyperinsulinemia — a consequence of insulin resistance — was associated with coronary heart disease[*].
  • Dementia: Insulin resistance is also bad for that soggy wetware between your ears. In 67 dementia patients, in fact, hyperinsulinemia predicted increased damage to the white matter of their brains[*].

The fact is, insulin resistance is linked to some nasty health outcomes. For the sake of your health, you definitely want to be sensitive, not resistant, to insulin.

How To Become Insulin Sensitive

So how can you stay insulin sensitive? Let’s review how four main areas – diet, exercise, stress and sleep – affect your insulin response.

#1: How Meal Size and Composition Affects Insulin

Recall: eating raises your blood sugar, which stimulates the pancreas to release insulin. The amount of insulin released, and your sensitivity to this insulin, depends on the size and composition of your meals.

That’s right, size matters. When you eat little to no food, your blood sugar stays low, and your body doesn’t need much insulin. In fact, intermittent fasting — fasting for 18-20 hours each day — has been shown to improve insulin sensitivity in type 2 diabetics[*].

Feasting has the opposite effect. When you eat like a pampered royal, insulin levels stay high, and your cells eventually become resistant to that insulin. This leads to hyperinsulinemia, which, as we’ve seen, promotes fat storage. It makes evolutionary sense. In times of plenty, to fatten up was insurance against future scarcity.

But if you’re reading this article, you probably don’t need (or want) this insurance policy.

Along with meal size, meal composition also affects your insulin response. Let’s look at the main macronutrients – carbs, proteins and fats:

  • Carbohydrates. Eating sugar — or refined carbohydrate — spikes your blood glucose, which in turn spikes your insulin. Even moderate amounts of fructose and sucrose, it’s been shown, decrease insulin sensitivity[*]. But not all carbohydrates are created equal. For instance, carbs with a low glycemic index — carbs that cause a slower blood sugar response — are less likely to cause insulin resistance[*].
  • Protein. Eating protein stimulates the release of insulin to promote muscle growth. This is normal, but caution may be warranted at excessively high protein intakes[*].  
  • Fat. A high fat, ketogenic diet may have therapeutic effects on insulin resistance and related conditions[*]. That’s true, at least in part, because restricting carbs — a feature of the ketogenic diet — has beneficial effects on blood sugar, triglycerides, cholesterol and body fat.

Of all the macronutrients, carbohydrates — especially refined sugars — are probably the worst choice for preventing insulin resistance[*].

How A Ketogenic Diet Helps You Become Insulin Sensitive

A very low carb, high fat ketogenic diet can help you achieve achieve insulin sensitivity for 3 main reasons:

#1: Keto Removes the Biggest Cause of Insulin Resistance

Studies show that restricting your daily carbs improves all the features of metabolic syndrome, such as[*]:

  • High blood pressure
  • Elevated blood sugar
  • Excess body fat around your waist
  • Abnormal cholesterol levels

In one of the first trials ever designed to see what kind of effect a ketogenic diet has on insulin resistance, researchers monitored the diets of 10 obese participants with type 2 diabetes for one full week. Then the participants followed high-fat ketogenic diets for two weeks.

Researchers found that keto dieters[*]:

  • Improved their insulin sensitivity by 75%
  • Naturally ate 30% fewer calories
  • Lost an average of almost four pounds in just 14 days
  • Lowered their mean triglycerides by 35% and their overall cholesterol by 10%

In another study, 146 overweight patients were placed in two separate diets, a low fat diet and a ketogenic diet. Insulin levels in the ketogenic diet group decreased three times more than in the low fat group[*].

#2: Keto Can Help Reverse Type 2 Diabetes

In one study of overweight participants with type 2 diabetes, a low carb keto diet (LCKD) improved their blood sugar control so much that most of them either reduced or completely eliminated their diabetes medications in just 16 weeks[*].

#3: Keto Triggers Natural Weight Loss

Carrying excess body fat around your belly and between your organs encourages insulin resistance.

Keto can reduce insulin resistance by ramping up fat loss. Being in ketosis means your body is burning stored fat cells for energy instead of glucose, which naturally aids healthy weight loss and prevents unwanted weight gain.

Ketosis also helps to control your appetite and eliminate cravings.

Macronutrients aside, here are some foods, herbs, spices and compounds shown in research to promote insulin sensitivity:

  • Vinegar[*]
  • Cinnamon[*]
  • Berberine[*]
  • Dark Chocolate[*]
  • Turmeric[*]
  • Rosemary[*]
  • Green tea[*]

If you want your cells to be insulin sensitive, you’ll want to get these and other colorful substances into your diet.

#2: Exercise and Insulin Sensitivity

After diet, exercise is one of the best ways to prevent insulin resistance. Even a small amount of exercise — just 20-30 minutes per day —  reduced diabetes risk by 58% for 522 middle aged, overweight people[*]. That’s a serious benefit for a tiny investment.

The benefits multiply when you diversify your exercise regimen. Resistance training, for instance, primes your skeletal muscle cells to soak up more sugar via the GLUT 4 pathway[*]. Less blood sugar means less insulin bombarding your cells, which helps your cells stay insulin sensitive.

High intensity interval training (HIIT), or sprinting, has also been shown to improve insulin sensitivity. In one study, twenty two old timers did high intensity cycling intervals three times per week for six weeks to reap this benefit[*].

#3: Stress, Sleep and Insulin Resistance

These days, many people are overstressed and under-rested. Unfortunately, both stress and sleep deprivation are linked to insulin resistance.

Take stress. Producing too much cortisol — the stress hormone — affects the insulin response, and causes your body to start storing fat[*].

Reducing stress improves this insulin response. Transcendental meditation, in fact, has been shown to increase insulin sensitivity and lower blood pressure in subjects with coronary heart disease[*].

Along with stress, poor sleep also causes insulin resistance. Sleep duration has declined in recent decades, and researchers have linked this trend to rising rates of diabetes. Researchers have also shown that inducing sleep deprivation in the lab leads to decreased insulin sensitivity in human subjects[*].

Simple Ways To Stay Insulin Sensitive

If you want to stay lean and reduce your risk for a host of diseases, staying sensitive to insulin should be way up on your list of priorities. Here are some ways to do that:

  • Don’t eat all the time. Try intermittent fasting.
  • Take it easy on the carbs, especially refined sugar.
  • Try the ketogenic diet and support this effort with keto-friendly supplements like Perfect Keto Exogenous Keto Base or Perfect Keto MCT Oil.
  • Choose clean protein supplements like  Perfect Keto Collagen.
  • Eat lots of colorful, polyphenol-rich foods like dark chocolate, green tea, and turmeric.
  • Take cinnamon, berberine or a variety of other compounds shown to support healthy blood sugar levels. Or simplify this health hack with Perfect Keto Blood Sugar Support capsules, which supports healthy carbohydrate metabolism.
  • Exercise every day, and incorporate HIIT and resistance training a few times per week.
  • Reduce stress with meditation, yoga or a walk in the woods.
  • Sleep long and well.

Make Insulin Work For You

Clearly, insulin isn’t just for type 1 diabetics. You, me and everyone else on the planet needs this hormone to regulate blood sugar, store energy and prevent cellular damage.

But how well insulin does these jobs is up to you. Your diet, exercise and lifestyle all affect your insulin response, and a healthy insulin response helps keep you lean and disease free.

So be well, and stay sensitive. Insulin sensitive, that is.

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