High insulin sensitivity plays a crucial role in boosting natural Testosterone production, muscle growth, and fat loss.

Research has shown that increasing insulin sensitivity can:

• Raise Testosterone by 10-20% (Diamanti-Kandarakis et al., 2009).
• Increase muscle protein synthesis by 20-25%, enhancing muscle growth, exercise recovery and repair (Kershaw & Flier, 2004).
• Enhance fat loss by over 15% (Baur et al., 2006).

While low insulin sensitivity contributes to:

• Low Testosterone
• Decreased muscle mass and
• Increase in body fat.

But what is insulin sensitivity?

What causes low insulin sensitivity?

What strategies are there to raise insulin sensitivity?

I go in full depth inside this article:

What Is Insulin?

Food gets broken down into a sugar called glucose.

Glucose is the main fuel for your body.

Glucose needs a “key” to enter most cells.

Insulin is the “key” to open the lock in the door of your cells.

It allows glucose to be absorbed by the liver, muscles and fat tissue and provide the body with energy.

• In muscle: insulin stimulates cells to use glucose for energy and to store glucose as glycogen (stored energy reserve).
• In fat tissue: when insulin is working effectively, little to none of the glucose intake is stored as fat.
• In the liver: extra glucose is stored as glycogen, and when blood glucose levels drop, the liver releases glucose into the bloodstream to restore normal blood sugar levels. This dynamic process is essential for regulating blood glucose concentrations and ensuring a constant supply of energy for the body

What Is Insulin Sensitivity?

Insulin sensitivity refers to how effectively the body uses insulin to reduce blood glucose levels.

High insulin sensitivity allows for efficient glucose uptake by cells, particularly muscle cells, promoting energy storage and utilization.

Low insulin sensitivity, or insulin resistance, means the body’s cells do not respond effectively to insulin, leading to higher blood glucose levels. This condition is a precursor to type 2 diabetes and is associated with metabolic syndrome (Matthews et al., 1985).

A 2017 study showed that improving insulin sensitivity can enhance metabolic health, including better glucose control and reduced risk of type 2 diabetes (Toprak et al., 2017).

What Is Insulin Resistance?

Insulin resistance is also known as low insulin sensitivity.

It is a condition where cells in muscles, fat, and liver respond poorly to insulin and cannot easily take up glucose (sugar) from the blood.

This leads to higher blood glucose levels and, over time, can increase the risk of type 2 diabetes.

According to Matthews et al. (2019), insulin resistance is closely linked to low Testosterone, obesity and cardiovascular diseases.

Insulin Resistance Symptoms

Here are the symptoms of low insulin sensitivity:

• Reduced Testosterone Levels: Insulin resistance is often associated with lower testosterone levels, which can decrease by 15-25%, affecting muscle mass, fat distribution, and overall metabolic health (Diamanti-Kandarakis et al., 2009).
• Decreased Muscle Mass: Low insulin sensitivity can lead to impaired nutrient delivery to muscles, reducing muscle growth and strength by up to 15-20% (Kershaw & Flier, 2004).
• Increased Fat Accumulation: Poor insulin response is linked to increased fat storage, particularly in visceral areas, leading to a higher risk of obesity-related complications (Baur et al., 2006).

Insulin Sensitivity And Testosterone

High Insulin Sensitivity and Testosterone

• Enhanced Testosterone Production: High insulin sensitivity is linked to increased testosterone levels. Studies indicate that men with higher insulin sensitivity have 10-20% higher testosterone levels compared to those with lower insulin sensitivity (Kershaw & Flier, 2004).
• Benefits of High Testosterone: Elevated testosterone levels contribute to improved muscle mass, reduced body fat, enhanced libido, and overall better mood and cognitive function (Renehan et al., 2008).
• Reduced Risk of Metabolic Disorders: High insulin sensitivity and optimal testosterone levels together reduce the risk of metabolic disorders, including type 2 diabetes and cardiovascular diseases (Baur et al., 2006).

Low Insulin Sensitivity and Testosterone

• Decreased Testosterone Levels: Low insulin sensitivity, or insulin resistance, is often associated with a reduction in testosterone levels. This can lead to a decrease in testosterone by as much as 15-25% (Kershaw & Flier, 2004).
• Side Effects of Low Testosterone: Lower testosterone levels can result in decreased muscle mass, increased body fat, reduced libido, and potential mood disturbances (Renehan et al., 2008).
• Increased Health Risks: Insulin resistance and low testosterone levels together increase the risk of developing chronic conditions like obesity, type 2 diabetes, and cardiovascular diseases (Baur et al., 2006).

Insulin Sensitivity and Muscle Mass

1. Muscle Glucose Uptake: Insulin sensitivity is closely linked to muscle glucose uptake. Enhanced insulin sensitivity allows muscles to efficiently take up glucose from the bloodstream, providing an energy source for muscle growth and maintenance (Cartee et al., 2016).
2. Impact on Protein Synthesis: Insulin sensitivity plays a role in protein synthesis within muscle cells. Increased sensitivity can support muscle protein synthesis, aiding in muscle development (Breen et al., 2013).
3. Anabolic Signaling: Insulin acts as an anabolic hormone, stimulating muscle growth. Individuals with higher insulin sensitivity may experience more efficient anabolic signaling, potentially leading to greater muscle mass (Stuart et al., 2013).

Causes of Low Insulin Sensitivity

Obesity

Excess body fat decreases insulin sensitivity (Holick, 2007).

Obesity can reduce insulin sensitivity by up to 60%, with visceral fat being particularly detrimental (Holick, 2007).

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Furthermore, body fat decreases Testosterone production.

Obese men have over 50% lower Testosterone than lean men (Kelly and T. Hugh Jones, 2015)

Read Next: Testosterone & Body Fat – Is There A Link?

Physical Inactivity

Lack of exercise contributes to reduced insulin sensitivity.

Regular physical inactivity can decrease insulin sensitivity by approximately 30% (Grundy et al., 2005).

Poor Diet

A diet high in sugars, fats, and processed foods leads to decreased insulin sensitivity.

High sugar intake alone can:

• Reduce insulin sensitivity by up to 25% (Toprak et al., 2017).
• Suppress testosterone production by 25% (Caronia et al., 2013)

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Sleep Deprivation

Poor sleep quality negatively impacts insulin sensitivity.

A study by Buxton et al. (2010) demonstrated that sleep restriction for one week significantly reduces insulin sensitivity in healthy men.

The study involved 20 healthy men who experienced a reduction in sleep time from 10 hours per night to 5 hours per night for one week.

This sleep restriction led to a 24% decrease in insulin sensitivity, highlighting the negative impact of insufficient sleep on metabolic health (Buxton et al., 2010).

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Stress

Long-term stress can decrease insulin sensitivity by approximately 20-25% (Grundy et al., 2005).

Chronic stress leads to hormonal changes that reduce insulin sensitivity.

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Medications

Certain medications, like corticosteroids, decrease insulin sensitivity.

Long-term use of corticosteroids can reduce insulin sensitivity by up to 25-30% (Toprak et al., 2017).

This is because corticosteroids mimic our body’s stress hormone cortisol.

Cortisol reduces insulin sensitivity and Testosterone production. (Stachowicz and Lebiedzińska, 2016)

Chronic Inflammation

Persistent low-grade inflammation is associated with reduced insulin sensitivity.

Chronic inflammation can lower insulin sensitivity by about 20-30% (Grundy et al., 2005).

Inflammation also suppresses your body’s natural Testosterone production.

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Aging

Insulin sensitivity naturally decreases with age.

After the age of 50, insulin sensitivity can decrease by about 1-2% per year (Grundy et al., 2005).

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How To Increase Insulin Sensitivity

Intermittent Fasting

Intermittent fasting (IF) has been shown to improve insulin sensitivity.

Anson et al. (2003) reported that intermittent fasting, specifically alternate-day fasting, resulted in beneficial effects on glucose metabolism, including increased insulin sensitivity, in mice, even without a decrease in overall calorie intake (Anson et al., 2003).

Similarly, Sutton et al. (2018) found that fasting 16 to 18 hours per day improved insulin sensitivity in men with prediabetes, even without weight loss (Sutton et al., 2018).

These studies suggest that intermittent fasting can enhance insulin sensitivity independent of calorie restriction or weight loss.

Read Next: Beginner’s Guide To Intermittent Fasting

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Fat Loss

Losing excess body fat improves insulin sensitivity.

Weight loss of 5-10% can increase insulin sensitivity by 30-50% (Holick, 2007).

For example, if you are overweight at 100kg (225lbs), you will need to lose 5 to 10kg (11.25 to 22.5 lbs) to experience this increase in insulin sensitivity.

Furthermore, reducing body fat will enhance your body’s Testosterone production.

12% to 20% body fat is the ideal body fat percentage for men to increase testosterone naturally and for optimal health. (PubMed, 2016; PubMed, 1996)

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Resistance Training And Cardio

Resistance training and cardio improve insulin sensitivity by up to 50-70% (Grundy et al., 2005).

Glynn et al. (2015) conducted a study on the impact of combined resistance training and cardio on insulin sensitivity in overweight individuals. They found that exercise intervention significantly increased insulin sensitivity (Glynn et al., 2015).

Suh et al. (2011) conducted a similar study in overweight Korean adolescents. The study found both resistance training and cardio enhanced insulin sensitivity (Suh et al., 2011).

Resistance Training

Resistance training enhances insulin sensitivity by increasing muscle mass.

Muscle tissue is metabolically active and efficiently utilizes glucose from the bloodstream.

More muscle means more glucose uptake, which can enhance insulin sensitivity (Cartee et al., 2016).

Building and maintaining muscle through resistance training can have lasting effects on insulin sensitivity, even during periods of rest.

It can contribute to a higher basal metabolic rate (BMR). This increases the number of calories you burn per day, which can facilitate better blood sugar control (Bhasin et al., 2003).

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Cardio

1. Immediate Impact: Cardiovascular exercise, such as running or cycling, can have an immediate effect on improving insulin sensitivity. It helps muscles absorb glucose during and after exercise, reducing blood sugar levels (Kirwan et al., 2009).
2. Fat Loss: Cardio exercise is often associated with fat loss. As mentioned earlier, reducing body fat, especially abdominal fat, is linked to improved insulin sensitivity (Holick, 2007).

Resistance Training Or Cardio – Which Is More Effective?

Studies show they are both equally effective. However, the optimal approach would be a combination of resistance training and cardio.

Resistance training helps build and maintain muscle mass, while cardio exercise helps with immediate glucose uptake and fat loss.

Nutrition

A diet rich in fiber, whole grains, lean proteins, and healthy fats enhances insulin sensitivity by 20-30% (Toprak et al., 2017).

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Foods to Eat:

• Fiber and Whole Grains: Diets high in dietary fiber and whole grains are associated with improved insulin sensitivity. Foods like oats, barley, and whole wheat are beneficial. McAuley and Mann (2006) emphasized that high fiber intake is linked to better insulin sensitivity and metabolic health (McAuley & Mann, 2006).
• Lean Proteins: Incorporating lean proteins such as chicken, turkey, fish, and plant-based proteins can help in maintaining muscle mass and improving insulin sensitivity.
• Healthy Fats: Monounsaturated and omega 3 polyunsaturated fats, found in foods like olive oil, nuts, seeds, and fatty fish, are recommended for enhancing insulin sensitivity.

Foods to Avoid:

• Processed and High-Sugar Foods: The Western diet, characterized by high glycemic load and poor fatty acid composition, is linked to reduced insulin sensitivity. Cordain et al. (2005) highlighted that reducing the intake of processed and high-sugar foods can enhance insulin sensitivity by up to 20-25% (Cordain et al., 2005).
• Saturated Fats: Diets high in saturated fats, commonly found in red meat, butter, and certain processed foods, should be limited.
• Refined Carbohydrates: Foods with refined carbohydrates, such as white bread, pastries, and sugary snacks, can negatively impact insulin sensitivity.

Adequate Sleep

The optimal sleep duration for maintaining insulin sensitivity and overall health is generally considered to be between 7 to 9 hours each night.

Consistent good quality sleep within this range is crucial for metabolic health and can improve insulin sensitivity by 15-20%. (Holick, 2007).

A 2015 study found that extending sleep duration by 1 hour per day for six weeks in non-obese volunteers led to improvements in fasting insulin sensitivity.

This suggests that even modest increases in sleep duration can have beneficial effects on insulin sensitivity (Leproult et al., 2015).

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Supplementation

Supplements like magnesium and omega-3 fatty acids may improve insulin sensitivity by approximately 10-20% (Toprak et al., 2017).

Magnesium

Magnesium is a powerful antioxidant that takes part in over 300 different chemical reactions in the human body.

It works to enhance insulin sensitivity and Testosterone production by reducing oxidative stress and inflammation. (Soltani et al, 2022)

The recommended daily intake of magnesium ranges from 310 to 420 milligrams for adult men.

Omega 3

Omega-3s enhances insulin sensitivity by reducing chronic inflammation and lowering LDL cholesterol.

For adult men, a daily intake of 3000-4000 mg of EPA and DHA is considered optimal.

Cinnamon

Cinnamon has been suggested to improve insulin sensitivity.

Anderson (2008) reported that chromium and polyphenols found in cinnamon improve insulin sensitivity.

The study found that cinnamon reduces fasted blood sugar levels, total cholesterol, and LDL-cholesterol.

In the study, subjects took 1-6 g of cinnamon daily for 40 days (Anderson, 2008).

Berberine

Berberine is a natural plant extract that can significantly enhance insulin sensitivity, reduce body fat, and decrease LDL cholesterol to improve heart health.

In a 2013 study, berberine supplementation significantly:

• Increased insulin sensitivity
• Decreased waist circumference and body fat
• Reduced systolic blood pressure
• Lowered cholesterol and triglycerides (Pérez-Rubio et al., 2013)

in a 12-week study, taking 500 milligrams of berberine three times per day led to an average weight loss of about 5 pounds, along with a 3.6% reduction in body fat. (NCCIH, 2022)

The optimal dosage of Berberine is 500mg to 1,500mg per day.

Alpha-Lipoic Acid (ALA)

Alpha-lipoic acid has been studied for its effects on insulin sensitivity.

Kamenova (2006) reported that oral administration of alpha-lipoic acid improved insulin sensitivity in patients with type 2 diabetes.

The study involved 12 diabetic patients treated with alpha-lipoic acid, 600 mg twice daily for a period of 4 weeks, and found a significant increase in insulin sensitivity (Kamenova, 2006).

The optimal dosage of ALA is 600mg to 1200mg per day.

Quitting Smoking

Quitting smoking can help improve insulin sensitivity and overall metabolic health, increasing insulin sensitivity by up to 15-20% (Holick, 2007).

A study by Eliasson et al. (1997) showed that quitting smoking improves insulin sensitivity in healthy, non-obese middle-aged men. The study involved 40 men, with 17 successfully quitting smoking. These individuals showed increased insulin sensitivity.

Filozof et al. (2004) discussed the association between smoking cessation and weight gain. While weight gain is a common concern, the study suggests that quitting smoking can improve insulin sensitivity despite potential weight gain. (Filozof et al., 2004)

Nicotine suppresses appetite. When you quit smoking, your appetitie will increase and you will consume more food. This means more total calories consumed per day, which can lead to weight gain. (Robinson et al., 2012).

References

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