Do You Know What Causes Insulin Resistance? (HINT: It's not carbs!)

I was reading at Lyle McDonald's forum and came across a thread on insulin sensitivity and resistance.

His view peaked my interest because it was so different from the typical low-carb perspective. As a result, I started to do some research to see if I could find a few reliable sources to go along with his opinion.

Insulin receptors are found all over the body.

They are in your liver, muscles, fat cells, and even the brain. The sensitivity of the receptor is what determines how much insulin it will take to get the job done.

The more resistant a receptor is, the less effect the insulin will have on your cells.

The typical low-carb view of how the body works is that when you eat carbs, especially high-glycemic ones, blood glucose rises which triggers insulin release.

The majority of low carbers believe this is not a healthy response to carbs, and that over time, cells will become less sensitive to the effects of all of that insulin. As a result, blood glucose levels will creep up, basal insulin levels will rise, and the result will be disease and bad health.

The standard low-carb belief is that cutting out most carbs from the diet will reverse the cycle.

As a result of eating a low-carb diet, insulin levels will remain low, even after eating, blood glucose levels will be controlled, and all disease and ill health issues that came attached to the high insulin and elevated blood glucose levels will magically disappear.

What isn't presented in this view, is why high levels of insulin cause Insulin Resistance.

Does Insulin Resistance Cause Obesity?

When I went into the scientific literature the other day, I couldn't find a single study that supported the general low-carb view that insulin resistance causes obesity.

What I found was that obesity causes insulin resistance, because high fat stores and high circulating triglycerides down-regulate the insulin receptors I talked about earlier, causing what's known as resistance to the circulating insulin, which isn't really resistance at all.

It's not enough receptors.

The Key to Obesity

Now, in a normal functioning body, glucose levels in the blood rise when you eat.

This triggers a rise in insulin.

The rise in insulin causes insulin-sensitive tissues to take the glucose out of the bloodstream and pull it into their cell mitochondria to be processed.

This rise in blood sugar and insulin isn't a bad thing. It's how the body was designed to work.

What isn't immediately needed for fuel is sent to the liver to be converted to glycogen. This causes blood glucose levels to fall, and beta cells in the pancreas to reduce their output of insulin.

None of this is bad either. It's what keeps your blood glucose level steady, with a normal glucose level of about 80 to 90 mg/dl.

Glycogen is stored in the liver and muscles for future use. Not a bad thing either.

In fact, if you don't replace your glycogen stores, the liver will make the glycogen it needs for that purpose out of protein tissues, and sometimes fats.

Glycogen stores is how and why we are able to do sprints and other fast energy movements. It's where you get the energy you need to take a quick jog down the beach.

But when liver and muscle glycogen stores are full, and this is the real key to obesity, any excess glucose is then converted into triglycerides and stored in your fat cells.

So, if you're eating exactly what the body needs to provide itself with fuel and glycogen storage, with no excess glucose and therefore no excess glycogen, and you're getting adequate exercise throughout the day, the carbs in your diet will not make you fat.

In fact, carbs are burned FIRST.

It is only the excess carbs over and above what you need to keep your liver and muscle glycogen stores replenished and the excess fat in your diet that cause the problem.

It's only if your calories exceed your energy output since fat stores are used during times of fasting, like when you're sleeping.

What Causes Insulin Resistance?

Therefore, insulin sensitivity is about how well the body responds to insulin. It's about the number of insulin receptors you have, which is often associated with your body-fat level.

Under normal conditions, it doesn't take very much insulin to get blood glucose into your cells faster.

However, the amount of insulin that is released at any given meal is somewhat individual. Some people release more insulin than others do. Insulin release is not always a direct relationship to the amount of carbs you eat.

While carbs tend to have the greatest impact on insulin secretion, dietary wise, that doesn't mean that carbs cause insulin resistance because insulin resistance isn't about the amount of insulin secreted.

Insulin resistance is about the failure of the body to get the glucose in the bloodstream into the cells and mitochondria where it can be burned. 

It's about eating more than the body needs for fuel and, thereby, increasing blood fats and a fatty liver. It's about not using the glycogen in your muscles.

Therefore, insulin resistance isn't a carb problem.

It isn't an insulin secretion problem.

It's an insulin receptor problem, with higher circulating insulin levels being a symptom and not the problem itself.