Insulin… Devilish hormone? (Part 1)

Ahhhh insulin… What an interesting and controversial subject, ESPECIALLY in the fitness industry where this hormone is often demonized. Wrongly?

I would like to thank James Krieger for his work on the subject, which has been of great help to me while writing this article.

Insulin: a quick introduction

Insulin is a hormone that regulates the sugar levels in your blood. We talk about blood sugar, which corresponds to the amount of glucose contained in the blood and which is usually expressed in grams per liter of blood. When you eat a meal, the carbohydrates in your meal are broken down into glucose molecules. Glucose passes into your blood. Your pancreas senses the rise in glucose and releases insulin. Insulin allows glucose to enter your liver, muscles, and fat cells. Once your blood sugar begins to drop, insulin levels also drop. This cycle occurs throughout the day. You eat a meal, your blood sugar rises, insulin rises, blood sugar falls, and insulin falls.

Insulin doesn't just regulate blood sugar. It has many other functions. For example, it stimulates your muscles to make new protein (a process called protein synthesis). It also inhibits lipolysis (the breakdown of fats) and stimulates lipogenesis (the creation / synthesis of fats).

It is moreover for this last function that it has such a bad reputation. Since carbohydrates stimulate your body to release insulin, some people argue that a high carbohydrate diet will force you to put on weight based on the following reasoning:

High Carbohydrate Diet → Elevated Insulin Levels → Increased Lipogenesis / Decreased Lipolysis → Increased Body Fat → Obesity

Following this same logic, they argue that a low carb diet is best for fat loss because insulin levels are low. Here is their reasoning:

Low Carbohydrate Diet → Low Insulin → Decreased Lipogenesis / Increased Lipolysis → Decreased Body Fat

However, this logic is based on many myths. Let's take a look at several of the myths surrounding insulin.

Myth : A high-carb diet leads to chronically high insulin levels

Reality : In a healthy individual, insulin is only elevated in the period after a meal

A misconception about high carbohydrate intake is that it will lead to chronically high insulin levels, meaning that you will gain weight because lipogenesis will constantly exceed lipolysis (remember that fat gain cannot be achieved. produce only if the rate of lipogenesis exceeds the rate of lipolysis). However, in a healthy person, insulin is only elevated in the period after a meal. This means that lipogenesis will only exceed lipolysis during the hours following a meal (known as the postprandial period). During periods of fasting (such as extended times between meals, or when you sleep), lipolysis will override lipogenesis (i.e., you will burn fat). Over a 24 hour period, everything will be balanced (assuming you don't consume more calories than you expend) which means you won't gain weight. Here is a graph showing how it actually works:

After meals, fat is deposited with the help of insulin. However, between meals and during sleep, you lose fat. The fat balance will be zero over a 24 hour period if the energy consumption matches the energy expenditure (i.e. if you consume as many calories as you burn).

This is only a rough graph, but the green area represents the lipogenesis that occurs after a meal. The blue area represents lipolysis in response to fasting between meals and at night. Over a 24 hour period these will be balanced assuming you are not consuming more calories than you are spending. And even if your carbohydrate intake is high, it still holds true. In fact, there are entire populations that consume high carbohydrate diets and do not have obesity issues. example: the traditional food of the Okinawan s . Moreover, in case the energy intake is lower than the energy expenditure, a high carbohydrate diet will lead to weight loss like any other diet..

Myth : Carbohydrates lead to an increase in insulin, which leads to fat storage

Fact : Your body is able to synthesize and store fat even when insulin levels are low

One of the biggest myths about insulin is that it is needed for fat storage. This is not the case. Your body has ways of conserving and storing fat, even if your insulin levels are low. There is an enzyme in your fat cells called hormone-sensitive lipase (LHS). HSL helps to hydrolyze reserve triglycerides (peripheral lipolysis), ie to break down fats. Insulin suppresses the activity of HSL and thus suppresses the breakdown of fat. It is for this reason that carbohydrates are singled out when gaining fat.

However, the fat also removes the HSL even when insulin levels are low s . This means that you will not be able to lose fat even when the carbohydrate intake is low, in the event that you eat too many calories. If you eat absolutely no carbohydrate but 5,000 calories from fat, you will not lose fat even though insulin levels are low. Simply because high fat intake suppresses HSL. It also means that if you are on a low-carb diet, you should also consume fewer calories than you expend to lose weight.

I know some people are going to say, "Try consuming 5,000 calories of olive oil to see what it feels like." Indeed 5,000 calories of olive oil is clearly not the best and it will be difficult to achieve but I don't think consuming 5,000 calories of table sugar is easy either.

Myth : Insulin makes you hungry

Fact : Insulin suppresses the feeling of hunger

It is well known that insulin strongly suppresses appetite. This has been demonstrated in dozens and dozens of experience s . Keep this in mind, which will be important when we talk about the next misconception ...

Myth : Carbohydrates are the only ones responsible for increasing insulin levels

Fact : Protein Strongly Stimulates Insulin Secretion Too

This is probably the biggest misconception on the subject. Carbohydrates get a bad rap for their effect on insulin, but protein also stimulates insulin secretion. In fact, protein can be just as powerful a stimulus as carbohydrates when it comes to insulin. A recent study compared the effects of two different meals on the level of insulin e :

• Meal 1 (LP / HC) contained 21 grams of protein and 125 grams of carbohydrate, so high in carbohydrates and low in protein.
• Meal 2 (HP / LC) contained 75 grams of protein and 75 grams of carbohydrate, so high in protein and low in carbohydrate.
• Both meals contained 675 calories.

Here is a graph of the insulin response:

Here is now a table of the response of the blood sugar level (Blood glucose level = blood sugar):

So you can see that despite the fact that the blood glucose level was much higher following the high carbohydrate meal, the insulin level was not higher. In fact, the insulin response was somewhat higher after the high protein meal, although this was not statistically significant.

Some people might argue that Meal 2 was not “low carb” with an intake of 75 grams but who cares! The point is that Meal 1 was twice as high in carbohydrate, with a much greater glycemic response than Meal 2, but insulin secretion was slightly lower. Which shows that protein is just as powerful at boosting insulin as carbohydrates.

Some might say, "Yes, but the insulin response is longer and more stretched with protein." Which is not the case in this study either.

As you can see from the graph, there was a tendency for a higher increase in insulin with protein, with an average response of 45 uU / mL 20 minutes after the meal, compared to about 30 uU / mL for the high carbohydrate meal.

This tendency for a greater insulin response has been associated with better appetite suppression. The subjects were less hungry and a better feeling of fullness after the protein-rich meal:

Right (A.): Hungry / Left (B.): Satiety

Here are the results of another ETUD e which compared the effects of four different types of proteins on the insulin response after a meal. In this study, proteins were consumed in the form of milkshakes (A tuna milkshake please…. MIAM!). Each shake contained 11 grams of carbohydrates and 51 grams of protein. Here is the insulin response to the different shakes:

Egg = Egg / Turkey = Turkey / Fish = Fish / Whey = Whey protein

You can find that all of these proteins cause an insulin response, although the carbohydrate intake of the shakes is very low. There were also different insulin responses depending on protein, with whey producing the highest insulin response.

Now, some might argue that the answer is due to gluconeogenesis (a process by which your liver converts protein into glucose). The idea would therefore be that the proteins would be converted into glucose, which would increase the insulin level. And as mentioned above, some claim it would cause a much slower and longer insulin response because it takes time for your liver to convert protein into glucose. However, this is not the case, as the insulin response was rapid, peaking within 30 minutes of the shakes and rapidly dropping back down to 60 minutes:

Insulin response to different types of proteins

This rapid insulin response is not due to changes in blood glucose. The evidence, whey, which elicited the greatest insulin response, also caused a drop in blood glucose (blood sugar):

Changes in blood glucose due to different types of proteins

In this study, the insulin response was associated with appetite suppression. Whey, which had the strongest response to insulin, caused the strongest appetite suppression. Here is a graph showing the calorie intake of subjects during their lunch (4 hours after drinking their shake):

Calorie intake from lunch, 4 hours after consuming various proteins

The subjects who consumed whey ate about 150 calories less than the others during their lunch. It was also whey that elicited the greatest insulin response. In fact, there is an extremely strong inverse correlation between insulin and food intake (correlation of -0.93).

Here are the data of another ETUD e which examined the insulin response after a meal containing 485 calories, 102 grams of protein, 18 grams carbohydrate and almost no fat:

R ed response insulin a meal high in protein and low in carbohydrates in lean and obese people.

You may find that the insulin response is very strong in obese subjects, possibly due to their insulin resistance. Below is a graph showing the blood sugar response. You can see that there was no relationship between glycemic and insulin response, so this is similar to the study discussed earlier.

Glycemic response of a high protein, low carbohydrate meal in lean and obese people.

The point is, protein is a powerful stimulant of insulin secretion, and this insulin secretion is not related to changes in blood sugar or due to gluconeogenesis from protein. One study even put in evidence that beef stimulated insulin secretion as much as rice comple t . The glycemic response of 38 different foods could only explain 23% of the variability in insulin secretion in this study. Suddenly, we can conclude that there are many more factors at play behind the secretion of insulin than just carbohydrates.

So how can protein cause rapid surges in insulin, as shown in the whey study above? Amino acids (the building blocks of protein) can directly stimulate your pancreas to produce insulin, without needing to be converted to glucose first. For example, leucine directly stimulates cells in the pancreas to produce insulin, and there is a direct dose-response relationship (i.e., the more leucine, the more insulin there is. produced).

Some will say, "Sure, protein causes insulin secretion, but that won't suppress fat utilization because it also causes glucagon secretion which counteracts the effects of insulin." As I mentioned earlier: insulin inhibits lipolysis. Well, some people think that glucagon increases lipolysis enough to negate the action of insulin completely.

The idea that glucagon increases lipolysis based on 3 principles: that the human adipose tissue has receptors for glucago No , the fact that glucagon increases lipolysis in animals, and that glucagon showed an increase lipolysis in human fat cells in glazed o (in cell culture). However, what happens in vitro is not necessarily what happens in vivo (in your body). More recent data allows us to challenge old beliefs. A study using modern techniques demonstrated that glucagon does not improve lipolysis in the obsidian e . Other research susing the same techniques have shown similar results. I will also add that this last study did not find a lipolytic effect in vitro ...

Remember the:

Why is glucagon released in response to protein initially?

Since protein stimulates insulin secretion, it would cause blood sugar to drop rapidly without consuming carbohydrates along with protein. It is glucagon that prevents this rapid drop in blood sugar by stimulating the liver to produce glucose.

Myth : Insulin spikes are "bad for you"

Reality : Insulin spikes are critical for normal physiological functioning

We could see that protein causes insulin spikes just like carbohydrates and that it was not related to gluconeogenesis. I have also shown how these spikes are partly responsible for suppressing the appetite caused by protein consumption (due to the effects of insulin on your brain to suppress appetite).

I want to expand on the importance of rapid insulin spikes after a meal and how they are important in the regulation of blood sugar. To do this, we need to discuss the different phases of insulin secretion. Insulin secretion from the pancreas occurs in two phases. The first phase happens very quickly; your pancreas senses the increase in glucose in the blood, and insulin is released within 1-2 minutes of the increase in blood sugar. This rapid response is made possible by the action of the pancreas which releases the stored insulin. This phase does not last more than 10 minutes. This fast phase is problematic for people with problems of intolerance to glucos e(IGT: people with higher glycemic responses after meals as well as higher fasting blood sugar levels, but who do not have diabetes). This rapid phase response is completely absent in people with type 2 diabetes.

There is a second phase which continues as long as the blood glucose is high. This second phase of insulin secretion is achieved through the release of stored insulin, as well as the creation of new insulin (insulin is created from a precursor called proinsulin). When you administer intravenous glucose to healthy people and type 2 diabetics, you get the following results:

You may find that diabetics do not have a rapid response (the insulin spike between 0 and 10 min) that is present in healthy people.

There is a medicine called exenatide (Byetta ) , which helps restore this rapid phase of insulin secretion in diabetics:

Insulin responses in type 2 diabetics and healthy individuals who have been given intravenous glucose. White circles represent the insulin response of type 2 diabetics when they receive a placebo. The squares represent the insulin response of diabetics when they received exenatide. You can see that exenatide restores the rapid response of insulin secretion. Dark circles represent the insulin response of healthy people.

This restoration of the rapid response of insulin secretion improves blood sugar regulation in diabetics:

Glycolic response following a meal in type 2 diabetics. White circles represent subjects who received a placebo. Black triangles and circles represent subjects who received exenatide.

You can see from the graph above that the blood glucose level remained stable following a meal in the subjects who received exenatide, but gradually increased in the subjects who received the placebo.

Many people like to attribute obesity and weight gain to insulin, but exenatide, which restores insulin spikes in type 2 diabetics, causes weight loss:

Effects of exenatide (Byetta) on weight

Part of this weight loss is due to an improvement in satiety . Exenatide is a medicine that mimics the effects of a hormone called GLP-1 (Glucagon-Like Peptide-1). GLP-1 is an insulin secretion stimulating intestinal hormone (known as incretin). GLP-1 potentiates insulin secretion, increases insulin synthesis, increases insulin gene expression and inhibits the secretion of glucagon (the opposite hormone of insulin). Yet exenatide, which mimics GLP-1 and helps stimulate insulin secretion, causes weight loss.

Insulin spikes are not in themselves a bad thing. Protein causes insulin spikes, but protein reduces appetite and contributes to weight loss. GLP-1 and drugs like exenatide contribute to spikes in insulin, but they reduce appetite and cause weight loss. The problem is, people confuse spikes in insulin with spikes in blood sugar. It is well established that the rapid changes in blood glucose can cause the fai m . Because rapid increases in blood sugar also cause rapid increases in insulin, people end up blaming insulin (and the effects of high GI carbohydrates on insulin) for this problem.

Myth : Since diabetics who inject insulin gain weight, it means that insulin is the reason non-diabetics gain weight as well.

Reality : Amylin is co-secreted with insulin in non-diabetics; amylin has lipolytic appetite suppressant effects

Amylin is a hormone that is secreted by your pancreas along with insulin. Amylin decreases Appeti t and also stimulates lipolys E (fat breakdown leads to the release of fatty acids).

Type 1 diabetics do not produce amylin and the secretion of amylin is impaired in type 2 diabetics. The drug pramlintide (SYMLIN), which mimics the effects of amylin, has been found to cause loss of weight in diabetics .

This information demonstrates that the effects of insulin injection in a diabetic cannot be compared to the effects of physiological changes in insulin in a non-diabetic, but many people make this comparison as if their situations were similar.

Myth: Lowering insulin levels regulates appetite better

Fact: Insulin is one of the many hormones essential for satiety

We have already addressed this myth above by demonstrating how protein strongly stimulates insulin secretion and helps reduce appetite. In addition, insulin injections also reduce appetite. Anecdote: when you suppress insulin receptors in a mouse's brain, it over-consumes until it becomes obese .

Myth: All of this information only applies to healthy people

Reality: This information applies to obesity and diabetes

Some people believe that the information in this article applies only to healthy individuals, and not to people with diabetes or obesity. That insulin control is essential for people with diabetes or obesity. Nevertheless, it is not the case. We can infer this from the information mentioned earlier in this article (for example, how exenatide restores insulin spikes and improves blood sugar and weight control in diabetics), but it has also been proven that high protein diets help diabetics and obese people, despite the fact that protein is a powerful stimulant of insulin secretion.

As I mentioned earlier, people seem to confuse blood sugar control with insulin control. It is the management of blood sugar itself that is partly responsible for the health benefits of low GI carbohydrates, or the reduction in carbohydrate intake in general, or the increase in carbohydrate intake. protein, fiber consumption or fruit and vegetable consumption or consumption of whole foods (unprocessed) compared to processed foods. It is not the control of insulin; Insulin control ends up being a byproduct of these other behaviors through improvements in insulin sensitivity (the way your cells are sensitive to insulin) and reduced blood sugar fluctuations.

Insulin might not be an evil hormone after all ?!

As we have just seen, insulin is ultimately not that horrible hormone that makes you obese and that needs to be kept as low as possible. It is a very important hormone that regulates appetite and blood sugar. If you really want to keep your insulin levels as low as possible then you will need to eat a diet that is low in protein, low in carbohydrates, and high in fat (fat). Strangely, I rarely see this kind of recommendations circulating ...

I am sure that by reading this article some will have cognitive dissonance. I know because I've experienced the same disbelief, there are years when I discovered this etud e and how proteins caused large insulin responses. At the time, I had the same beliefs as many of you ... that you have to keep your insulin as low as possible, that spikes in insulin are bad for your health and that you have to suppress everything. food with a high GI. I was having trouble reconciling this study with my beliefs about insulin. Yet, as I read more research on the subject, I realized that what I thought I knew about insulin was just plain wrong.

Now you might be wondering why refined sugars (carbohydrates) are considered unhealthy. Many believe this is because they cause insulin spikes. However, this is obviously not the case since protein can also cause rapid spikes in insulin and is not, however, unhealthy for your health. One problem with refined sugars is energy density - it's much easier to consume a lot of calories with very little bulk. Additionally, high energy density foods often have a lower fullness index than low energy density foods, so you are consuming more calories AND you are still hungry! In fact, when it comes to foods high in carbohydrates, the energy density of a food is a strong predictor of the satiety index of that food (ie, foods with low energy density create more satiety). There are other issues with refined sugars but that is beyond the scope of this article.

In conclusion: insulin does not deserve its bad reputation. This is one of the main reasons why protein helps reduce hunger pangs and you will have insulin spikes even on a low carb, high protein diet. Instead of worrying about your insulin levels, you should seek out what foods are best for you in terms of satiety and over the long term. Everyone responds to a diet differently, and results often vary. Keep in mind that what works for someone won't necessarily work for someone else.

Related research and references:

1. Bayesian Bodybuilding PT Course / bayesianbodybuilding.com
2. James Krieger / www.weightology.net
3. Stephane Guyenet / www.stephanguyenet.com