Insulin; sensitivity and resistance

Hearing (11:54)

Insulin production

Insulin secretion from the beta cells of the pancreas responds to rising blood sugar levels.

Under normal circumstances, insulin production begins to increase at a blood sugar level of 4.4–4.5 mmol/L, but this is also influenced by individual differences and metabolic status.

Fasting blood sugar levels normally range between 4.4–5.2 mmol/L, and insulin levels are also low at this time. (Basic)

During a meal, when blood sugar levels reach 4.6, insulin production increases sharply to help glucose enter the cells.

Insulin regulation is a complex process that is influenced by blood sugar levels, hormones, and the nervous system.

How does insulin production start?

Insulin secretion is mainly regulated by an increase in blood glucose levels. When glucose enters the bloodstream, the following steps occur:

1. Glucose sensing in the pancreas:

Beta cells sense an increase in blood sugar levels. This especially happens when blood sugar levels rise above 4.4 mmol/L.

2. Phases of insulin secretion:

• Phase I: Rapid insulin release from pre-stored insulin over ~10-15 minutes.
• Phase II: Synthesis and release of new insulin ~ 30 minutes – several hours
• Phase III: Glucose uptake by cells. Insulin helps cells (muscles, liver, fat cells) take up glucose, thus lowering blood sugar levels.

The insulin response changes in response to rising blood sugar levels.

At these blood sugar levels, the following insulin response is expected:

• Below 3.9: no insulin production

The body produces glucagon and adrenaline to raise blood sugar levels, and ketone bodies for the brain and muscles. (Fat Burning Mode)

• 3.9-4.4: low/basal insulin production

Normal fasting blood sugar levels, the body maintains balance.

• 4.4-4.6: initial insulin response

Slight rise after eating, normal insulin response.

• 4.6-8.0: strong insulin response

Peak after a meal, insulin helps glucose enter cells.

• 8.0-10.0: increased insulin levels

If it lasts for a short time, it is normal; if it is persistent, it may indicate insulin resistance.

• 10-12: high insulin levels

It can be a sign of pre-diabetes or diabetes, where cells do not respond properly to insulin.

• 12-15: max. insulin production

If it persists, it is a sign of insulin resistance. The pancreas becomes overloaded and type 2 diabetes develops.

Any percentage change in body weight is followed by the same percentage change in fasting blood sugar levels, and vice versa.

This is because adipose tissue is hormonally active and produces substances that disrupt insulin signaling.

This makes cells less sensitive to insulin, so glucose cannot enter the cells effectively, but instead remains in the blood, raising blood sugar levels.

Here is an example of what would happen to a fasting glucose level of 5.2 mmol/L if body weight were to decrease by 1%:

83 kg – 1% = 82.17 kg (-0.83 kg)

5.2 mmol/L – 1% = 5.148 mmol/L (–0.052 mmol/L)

From this basic example, you can do a lot of personalized calculations, and then check the 'math' when you reach the desired goal. (It worked perfectly for me!)

After this, we can draw the following lesson:

Weight loss, especially losing excess abdominal fat, significantly improves basal blood sugar levels and its 'companion', insulin sensitivity.

Improvement in insulin sensitivity occurs through several interrelated mechanisms:

• Visceral fat reduction

Abdominal fat produces hormones and inflammatory substances that impair insulin's effectiveness. Reducing fat reduces the levels of these substances, improving cells' sensitivity to insulin.

• Reducing inflammation

Excess weight, especially belly fat, perpetuates chronic inflammation in the body.

Weight loss reduces inflammatory markers, which also contributes to improved insulin sensitivity.

• Improvement of metabolic processes

Even a 5–7% reduction in body weight can measurably improve insulin response.

When insulin sensitivity increases, glucose is converted to glycogen more efficiently, making it easier for the body to replenish its glycogen stores.

Glucose uptake by muscles also increases, especially during exercise. After exercise, the body specifically seeks to replenish its glycogen stores.

• Decrease in fat storage

Insulin resistance promotes fat storage, which can create a vicious cycle. Weight loss breaks this cycle; the body burns fat more easily and glucose enters the cells more easily.

• Lifestyle factors

Weight loss goes hand in hand with a healthier diet, regular exercise, better stress management, and better sleep quality – all of which further increase insulin sensitivity.

Muscles

Improving insulin sensitivity directly contributes to increased muscle performance.

The main reasons for this are:

• Increased glucose uptake

When muscles are more sensitive to insulin, they are able to take up more glucose from the blood, which is used as an energy source during exercise and physical activity.

This is especially important during intense or prolonged exercise, when the body primarily uses glycogen – glucose stored in the muscles.

• Larger muscle glycogen stores

With improved insulin sensitivity, muscles replenish their glycogen stores more efficiently, allowing them to perform high-intensity work for longer periods of time.

• More efficient energy use

Increased insulin sensitivity improves muscle cell metabolism, enhances oxidative capacity, increases capillary density, and promotes the entry of glucose transporters into the plasma membrane, resulting in faster and more efficient glucose uptake.

• Muscle mass and regeneration

Insulin not only stimulates glucose uptake but also muscle protein synthesis, thus contributing to the growth, maintenance and regeneration of muscle mass.

By improving insulin sensitivity, muscles get more energy, use blood sugar more efficiently, replenish glycogen stores faster, and muscle regeneration improves, which overall increases muscle performance.

Liver

Improved insulin sensitivity also increases liver glycogen stores, as liver cells respond more effectively to insulin, allowing them to take up more glucose from the blood and store it as glycogen (glycogenesis).

Insulin increases glycogen synthesis in the liver, while decreasing glycogen breakdown (glycogenolysis) and the release of glucose from the liver into the blood.

This means that with improved insulin sensitivity, the liver not only replenishes its glycogen stores more efficiently, but also releases less glucose into the bloodstream, thus contributing to more stable blood sugar levels.

Additionally, improved insulin sensitivity also supports liver health, which further optimizes metabolism and glycogen storage.

Improving insulin sensitivity reduces fat synthesis (lipogenesis) in the liver, thereby reducing the risk of developing fatty liver.

In case of insulin resistance, the liver is less responsive to insulin signals, so excess glucose is converted into fatty acids (triglycerides) and stored in the liver instead of glycogen, which can lead to fatty liver.

When insulin sensitivity improves, liver cells again efficiently take up glucose and store it as glycogen, while fatty acid synthesis and fat deposition decrease.

By restoring insulin sensitivity, the liver's energy metabolism is normalized:

• Glucose is converted into glycogen rather than fat.
• The chance of triglyceride accumulation in the liver and the development of fatty liver is reduced.
• The liver's fat metabolism shifts in a healthier direction, reducing the risk of inflammation and metabolic syndrome.

In summary

Weight loss – especially losing belly fat – improves fasting blood sugar levels and insulin sensitivity, reduces inflammation, optimizes metabolism, increases muscle performance, and reduces the risk of diabetes.