Most people have heard about insulin in today’s health climate. Whether you’re a health enthusiast who enjoys learning and optimizing your health status or you’ve been diagnosed with a metabolic disease, you’re likely aware of insulin’s functions. If so, you can skip the next paragraph.
Insulin is a hormone secreted by beta cells of the pancreas that acts in concert with glucagon to regulate blood sugar levels. High levels of insulin (as in type 2 diabetes) and low levels of insulin (as in type 1 diabetes) can have detrimental outcomes. Insulin signals to liver, muscle, and fat cells to uptake glucose from the bloodstream; it promotes glycogenesis and lipogenesis while simultaneously lowering blood glucose concentrations (1).
Above is a very surface-level understanding of the role of insulin. While its role in blood sugar regulation is essential for life, It turns out that insulin plays several other vital roles in the body, including regulating bone formation (2), driving several neurological processes in the brain (3), and regulating organs such as the kidneys, hair, skin, heart, and brain (1).
Excess energy intake is the fundamental cause of weight gain. Excess insulin and subsequent insulin resistance is the result of excessive energy intake (5). Studies have demonstrated this time and time again in both directions: reducing energy intake, regardless of the source, results in weight loss and improved metabolic health (6, 7).
The mechanisms behind this are not completely understood, but it is now known that insulin is also required to shuttle various amino acids into cells for growing tissues.
Research on type 1 diabetics (T1D) has helped elucidate these mechanisms. Individuals with T1D observe dramatic increases in blood sugar levels with pure protein ingestion (without carbs). A small amount results from converting some amino acids to glucose and incretin production within the gut (i.e., GLP-1). However, the majority results from pancreatic glucagon production (9).
Glucagon stimulates glucose release from the liver via gluconeogenesis, which in turn causes the pancreas to release insulin. This allows the ingested amino acids to be shuttled into the cells and used for anabolism (building new tissues) (9).
Higher-*quality*-protein diets have shown dramatic benefits to metabolic health (10), thus confirming that insulin is not the problem in metabolic disease; rather, insulin dysregulation is the consequence of a poor diet and disrupted metabolic health (5).
The brain has long been known to contain predominately GLUT1 and GLUT3 receptors, which are insulin-independent (12). Skeletal muscle has predominantly been recognized as having GLUT 4 receptors, which are insulin-dependent (13).
This is relevant to health because the sensitivity of your insulin receptors will determine how efficiently you’re able to remove glucose from your blood, where it can be toxic in high amounts. Skeletal muscle is the largest glucose disposal site of the body, so if your GLUT 4 receptors aren’t responding to insulin as they should, this can be problematic.
The wonderful thing about skeletal muscle is that it also possesses insulin-independent GLUT receptors that can be stimulated by movement (13). This is why regular daily movement and exercise are so vital to maintaining metabolic health.
This brings us to Myth #5…
A great way to think of insulin is as the air traffic control of nutrients. It directs and prioritizes the utilization of nutrients. When we haven’t eaten in a while, insulin production decreases, and glucagon increases, which instructs the liver to make its own glucose. This is deactivated following a meal.
Insulin directs the flow of nutrients—primarily glucose—into cells so they can produce the energy that gives us life. At the same time, it instructs the body to use amino acids to make new proteins (tissues, hormones, etc.), and any excess nutrients are stored as glycogen and or fat.
Fat is an excellent energy source, but it's a slow burner. The body will prioritize using available glucose for immediate energy production, followed by glycogen (stored glucose) and fat. When macronutrient intake exceeds the body's needs, insulin promotes the production of adipose tissue (fat) to store energy in case we need it in the future.
Metabolic diseases that coincide with insulin dysregulation:
The best activity for insulin balance:
Insulin is a hormone secreted by beta cells of the pancreas that acts in concert with glucagon to regulate blood sugar levels. High levels of insulin (as in type 2 diabetes) and low levels of insulin (as in type 1 diabetes) can have detrimental outcomes. Insulin signals to liver, muscle, and fat cells to uptake glucose from the bloodstream; it promotes glycogenesis and lipogenesis while simultaneously lowering blood glucose concentrations (1).
Above is a very surface-level understanding of the role of insulin. While its role in blood sugar regulation is essential for life, It turns out that insulin plays several other vital roles in the body, including regulating bone formation (2), driving several neurological processes in the brain (3), and regulating organs such as the kidneys, hair, skin, heart, and brain (1).
Myths and Misunderstood Roles of Insulin
Myth #1: Insulin Causes Weight Gain
This is probably the most widespread myth about insulin. Keto advocates often use this claim as a rationale for promoting a low-carb diet. A keto diet does indeed promote improved glucose metabolism, insulin sensitivity, and weight loss (4), but that doesn’t mean insulin is the villain in this story.Excess energy intake is the fundamental cause of weight gain. Excess insulin and subsequent insulin resistance is the result of excessive energy intake (5). Studies have demonstrated this time and time again in both directions: reducing energy intake, regardless of the source, results in weight loss and improved metabolic health (6, 7).
Myth #2: Insulin Only Increases In Response to Carbohydrates
Another common rationale for Keto, Carnivore, and Paleo Diets is that they don’t stimulate insulin secretion, thereby improving insulin resistance. However, insulin is also secreted in response to protein/amino acid ingestion (8).The mechanisms behind this are not completely understood, but it is now known that insulin is also required to shuttle various amino acids into cells for growing tissues.
Research on type 1 diabetics (T1D) has helped elucidate these mechanisms. Individuals with T1D observe dramatic increases in blood sugar levels with pure protein ingestion (without carbs). A small amount results from converting some amino acids to glucose and incretin production within the gut (i.e., GLP-1). However, the majority results from pancreatic glucagon production (9).
Glucagon stimulates glucose release from the liver via gluconeogenesis, which in turn causes the pancreas to release insulin. This allows the ingested amino acids to be shuttled into the cells and used for anabolism (building new tissues) (9).
Higher-*quality*-protein diets have shown dramatic benefits to metabolic health (10), thus confirming that insulin is not the problem in metabolic disease; rather, insulin dysregulation is the consequence of a poor diet and disrupted metabolic health (5).
Myth #3: Insulin is Required for Muscle Glucose Uptake
There are 14 different types of glucose receptors on cells, called glucose transporters (GLUT), which bring glucose inside cells (11). Some are insulin-dependent, and some are not.The brain has long been known to contain predominately GLUT1 and GLUT3 receptors, which are insulin-independent (12). Skeletal muscle has predominantly been recognized as having GLUT 4 receptors, which are insulin-dependent (13).
This is relevant to health because the sensitivity of your insulin receptors will determine how efficiently you’re able to remove glucose from your blood, where it can be toxic in high amounts. Skeletal muscle is the largest glucose disposal site of the body, so if your GLUT 4 receptors aren’t responding to insulin as they should, this can be problematic.
The wonderful thing about skeletal muscle is that it also possesses insulin-independent GLUT receptors that can be stimulated by movement (13). This is why regular daily movement and exercise are so vital to maintaining metabolic health.
Myth #4 & 5: Insulin is Only Produced in the Pancreas
Pancreatic insulin production is responsible for the majority of metabolic regulation and glucose uptake in the liver, muscle, and fat cells. Research recently discovered that specialized brain cells can make insulin (14).This brings us to Myth #5…
Myth #5: Energy Production in the Brain is Insulin-Independent.
It has long been known that glucose is the preferred and primary fuel source for the brain and neurons (15). It has also been thought that neurons only use glucose without insulin, but with the discovery of neurogliaform interneurons, which can release insulin (16), it is now known that brain cells can utilize insulin-dependent glucose uptake in times of increased cognitive demand. These findings may also have important implications for Alzheimer’s disease as it relates to decreased insulin levels in the brain, recently termed “type 3 diabetes” (14).Insulin Regulation
The most practical knowledge about insulin that deserves respect is that it’s the only hormone we can directly and immediately influence consciously. We can do very little from moment-to-moment to increase hormones like testosterone, thyroid, or progesterone. But we can drastically change our insulin production simply by ingesting carbohydrates.A great way to think of insulin is as the air traffic control of nutrients. It directs and prioritizes the utilization of nutrients. When we haven’t eaten in a while, insulin production decreases, and glucagon increases, which instructs the liver to make its own glucose. This is deactivated following a meal.
Insulin directs the flow of nutrients—primarily glucose—into cells so they can produce the energy that gives us life. At the same time, it instructs the body to use amino acids to make new proteins (tissues, hormones, etc.), and any excess nutrients are stored as glycogen and or fat.
Fat is an excellent energy source, but it's a slow burner. The body will prioritize using available glucose for immediate energy production, followed by glycogen (stored glucose) and fat. When macronutrient intake exceeds the body's needs, insulin promotes the production of adipose tissue (fat) to store energy in case we need it in the future.
Disrupted Insulin Regulation
When carbohydrate intake chronically exceeds the body’s usage capabilities, metabolic disease often follows. Insulin may be notably dysregulated in the pathophysiology of these diseases, but, as outlined above, this is often the consequence, not the cause.Metabolic diseases that coincide with insulin dysregulation:
- High cholesterol/dyslipidemia (15).
- Metabolic Syndrome (16)
- Non-Alcoholic fatty liver disease (NAFLD/MASLD) (17)
- PCOS (18)
- Type 2 diabetes (19)
- Cardiovascular disease (20)
Improving Insulin Metabolism
Preventative Screening
Studies show that insulin resistance often proceeds blood sugar and A1c disruption by 15 years (21). You can help yourself stay far ahead of metabolic disease by asking your doctor to run a fasting insulin test along with your annual blood sugar and A1c test - take full advantage of that 15-year head start!Stay Active
Physical activity has the most dramatic impact on insulin sensitivity. Your cells become more responsive to insulin, so your pancreas doesn’t have to work as hard to keep blood sugar levels under control. Studies show that regular physical activity decreases fasting insulin levels (22).The best activity for insulin balance:
- Resistance training
- A 10 min walk following a meal
- Hitting 10,000 steps per day
- 25-30 min a day of moderate-intensity cardio
