Reversing insulin resistance and type 2 diabetes with lifestyle

Source: Je Leefstijl Als Medicijn

Author: Jaap Versfelt Medical reviewers: dr. Adriaan Kooy (internist and associate professor UMCG) and dr. Yvo Sijpkens (internist Haaglanden Medical Center)

Key points

• Insulin resistance as the core problem: Insulin resistance is at the root of type 2 diabetes and is a major risk factor for cardiovascular disease, cancer, and dementia.
• ‘Prediabetes’ less innocent than it sounds: Elevated insulin levels and insulin resistance often begin years before T2D is officially diagnosed.
• Rapid increase in type 2 diabetes: The number of people with T2D is increasing strongly, partly due to insulin resistance caused by an unhealthy lifestyle.
• Importance of lifestyle interventions: Lifestyle changes can help manage and potentially reverse insulin resistance and T2D.
• Effect of nutrition on insulin: Low-carbohydrate diets have a proven effect on lowering insulin spikes.

1. Definition of type 2 diabetes and insulin resistance

Type 2 diabetes is a chronic condition characterized by elevated blood glucose levels. This occurs due to reduced sensitivity of the body to insulin (insulin resistance) and a relative shortage of insulin production by the pancreas. This form of diabetes, previously referred to as adult-onset diabetes, is however increasingly being diagnosed at younger ages and is related to genetic predisposition, obesity, physical inactivity, and an unhealthy diet.

2. The number of people with type 2 diabetes is growing rapidly

The number of people with T2D has risen sharply since 1990 when there were 250,000 diabetes patients in the Netherlands: a fivefold increase in just 35 years.

• Diabetes: In the Netherlands, 1.2 million people have diabetes, which amounts to 1 in 14 Dutch people. More than nine out of ten people with diabetes have type 2 diabetes.
• Prediabetes: It is estimated that more than 1.4 million Dutch people have prediabetes, a precursor to type 2 diabetes, which is often not yet recognized.

Why is the ‘pre’ in prediabetes misleading?

Prediabetes is a term used when fasting blood glucose is between 5.6 and 6.9 mmol/l. The ‘pre’ in prediabetes suggests you can calmly wait for glucose to rise further!

Even before prediabetes occurs, insulin levels have been elevated for years, sometimes from childhood. In this early stage, insulin resistance can contribute to rising blood pressure, atherosclerosis, gout, and cardiovascular disease.

Measuring insulin levels is unfortunately not yet routinely done in daily medical practice, which means insulin resistance goes unnoticed for a long time.

3. What is the difference between type 1 and type 2 diabetes?

Type 1 diabetes is an autoimmune disease in which the immune system attacks the insulin-producing cells in the pancreas. As a result, little or no insulin is produced, requiring patients to administer insulin.

Type 2 diabetes - the pancreas does produce insulin — often even in large amounts — but due to insulin resistance, glucose is not properly absorbed by cells. T2D develops gradually and is associated with unhealthy diet, overweight, stress, and lack of physical activity.

4. From ultra-processed food to type 2 diabetes

The development of insulin resistance and T2D is a step-by-step process:

1. Carbohydrates and glucose: When you eat carbohydrates, they are broken down into glucose, the primary energy source for body cells.

2. Insulin and glucose uptake: Glucose in the bloodstream stimulates the pancreas to release insulin. Insulin ensures glucose uptake into cells.

3. Fat storage: When more glucose is available than the body needs, insulin helps store the excess glucose as fat.

4. Ultra-processed food: Regular consumption of refined carbohydrates causes high insulin levels.

5. Insulin resistance: Due to prolonged elevated insulin levels, cells respond less well to insulin, requiring even more insulin.

6. Hyperinsulinemia: Chronically elevated insulin levels promote fat storage and cause high blood pressure, clotting tendency, and increased vascular resistance.

7. Diabetes: Eventually, beta cells can no longer produce enough insulin, resulting in T2D.

Deep dive: Ultra-processed food

61% of our energy intake in the Netherlands consists of ultra-processed food. This not only increases the risk of diabetes but also of obesity, cardiovascular disease, and depression.

Read more about ultra-processed food →

5. The harmful consequences of insulin resistance

• Cardiovascular disease: Insulin resistance is a major cause of hypertension and atherosclerosis.
• Dementia: Chronic insulin resistance is associated with an increased risk of dementia. Alzheimer’s is sometimes called “type 3 diabetes.”
• Cancer: High insulin and glucose levels can promote the growth of cancer cells.
• Parkinson’s: Studies point to a relationship between insulin resistance and neurodegenerative conditions.
• PCOS: Insulin resistance is an important factor in polycystic ovary syndrome.
• Erectile dysfunction: Vascular problems due to insulin resistance can reduce blood flow.

Deep dive: Cardiovascular disease

Insulin resistance is a major risk factor for cardiovascular disease. Discover how lifestyle determines up to 90% of the risk and what you can do about it.

Read more about cardiovascular disease →

Deep dive: Erectile dysfunction

Erectile dysfunction is often an early warning sign of underlying vascular problems and metabolic dysfunction - on average 5 years before heart problems occur.

Read more about erectile dysfunction →

6. Insulin resistance and obesity — chicken or egg?

Insulin resistance and obesity generally occur together: 70 percent of people with overweight or obesity are insulin resistant.

A vicious cycle exists: insulin resistance promotes weight gain, and weight gain worsens insulin resistance. In obesity, fat cells grow. When these cells become too large, they produce inflammatory substances that lead to insulin resistance.

7. Other causes of insulin resistance

• Lack of exercise: After just one week of sedentary lifestyle, insulin resistance can increase by a factor of 7.
• Smoking: Smokers experience a significantly higher insulin spike after eating carbohydrates.
• Lack of sleep: A few days of less sleep can lead to insulin resistance in healthy people.

8. How do you determine insulin resistance?

Self-recognition

• Abdominal fat: Waist circumference greater than 102 cm in men, 88 cm in women
• Skin: Dark skin patches (acanthosis nigricans) or skin tags
• Infertility: PCOS or erectile dysfunction
• Family: Family history of heart disease or type 2 diabetes
• Fluid: Fluid retention

Blood values

• High blood pressure: systolic >135 mm Hg or diastolic >85 mm Hg
• High fasting glucose: >5.5 mmol/l
• High triglycerides: >1.7 mmol/l
• Low HDL cholesterol: lower than 1.03 mmol/l (men), lower than 1.29 mmol/l (women)
• Fasting insulin: >6 uU/ml
• HOMA-IR index: >1.5

9. Current treatments for type 2 diabetes

Metformin remains the first-choice medication. This drug lowers blood glucose by improving insulin sensitivity and reducing glucose production by the liver.

New medications such as SGLT2 inhibitors and GLP-1 receptor agonists are often added for patients with increased risk of cardiovascular disease.

Limitations

Medication-based treatments can improve symptoms but do not always address insulin resistance as the root cause. Sulfonylurea derivatives and insulin therapy can even contribute to insulin resistance and weight gain.

10. Dietary guidelines reviewed

The origin of ‘low-fat’ dietary advice

Over the past fifty years, the focus has been on avoiding saturated fat. However, later research nuances this:

• PURE study (135,000 participants): More fat was associated with lower mortality risk, while more carbohydrates led to higher mortality risk.
• Minnesota experiment: Replacing saturated fat with vegetable oil led to higher mortality risk.

What dietary advice is needed?

For people with (pre)diabetes, carbohydrate restriction is sensible. The American Diabetes Association (ADA) included low-carbohydrate diets in its recommendations in 2019.

11. Carbohydrate restriction is proven effective for T2D

Studies demonstrating the benefits of carbohydrate restriction:

• Tay, 2015 (115 participants): Carbohydrate-restricted diet resulted in greater improvements in glucose, lipids, and reduced medication needs.
• Sainsbury, 2018 (meta-analysis, 2,412 participants): Carbohydrate-restricted diets produced greater reductions in HbA1c.
• Goldenberg, 2021 (meta-analysis, 1,357 participants): 57% remission with low-carb diet versus 31% in control group.
• Westman, 2008 (84 participants): Reduced diabetes medication in 95% of participants.

How does the body respond to macronutrients?

• Proteins: Moderate insulin increase (doubling)
• Carbohydrates: Tenfold increase compared to proteins
• Fats: Minimal effect on insulin

12. How can you reduce insulin resistance?

12.1 Choose carbohydrates with low glycemic load

• High glycemic load: Rice, pasta, pizza, potatoes, soft drinks
• Low glycemic load: Meat, fish, eggs, vegetables, nuts, avocados

12.2 Eat fewer carbohydrates

• Mild restriction: 100-150 grams per day
• Moderate restriction: 50-100 grams per day
• Strong restriction (therapeutic): less than 50 grams per day

12.3 Eat less frequently

• Fewer meals: Longer periods of stable glucose and insulin levels
• Intermittent fasting: Significant benefits for insulin sensitivity
• Time-restricted eating: Limiting food intake to a smaller part of the day

12.4 Use a continuous glucose monitor

A glucose monitor can provide insight into how your body responds to food, exercise, sleep, and stress. In studies, 67% of participants with a glucose monitor were able to reverse their diabetes.

13. Conclusion

Insulin resistance is at the root of type 2 diabetes and contributes to cardiovascular disease, cancer, and dementia. Insulin resistance is usually present for decades before T2D manifests.

In addition to avoiding ultra-processed products, therapeutic carbohydrate restriction is effective for becoming insulin sensitive again. Medications such as metformin, SGLT2 inhibitors, and GLP-1 agonists can support this.

Veelgestelde vragen

What is insulin resistance and how does it lead to type 2 diabetes?

Insulin resistance occurs when body cells become less sensitive to insulin, causing the pancreas to produce more insulin. This leads to hyperinsulinemia (chronically elevated insulin levels). Eventually, the pancreas cannot produce enough insulin, resulting in type 2 diabetes with elevated blood glucose levels. Insulin resistance often begins years before the diagnosis is made.

Can a low-carbohydrate diet reverse type 2 diabetes?

Yes, scientific research shows that a low-carbohydrate diet can be effective in reversing type 2 diabetes. Studies demonstrate that carbohydrate restriction (especially below 50 grams per day) can lead to significant improvements in HbA1c values, reduction in medication use, and in some cases even remission of the disease.

Which foods cause the largest insulin spikes?

Carbohydrate-rich foods cause the largest insulin spikes, approximately ten times higher than proteins. Foods with a high glycemic load such as white rice, pasta, pizza, potatoes, soft drinks, and cornflakes lead to the highest insulin response. Fats have only a minimal direct effect on insulin levels.

Is insulin resistance only harmful for diabetes patients?

No, insulin resistance is harmful for everyone. It increases the risk of cardiovascular disease, dementia, various forms of cancer (breast, colorectal, prostate, pancreatic cancer), Parkinson's disease, migraine, PCOS, and erectile dysfunction. Hyperinsulinemia can lead to high blood pressure, increased vascular resistance, and clotting tendency.

What is the connection between overweight and insulin resistance?

A vicious cycle exists: insulin resistance promotes weight gain, and weight gain worsens insulin resistance. Approximately 70% of people with overweight or obesity are insulin resistant. High insulin levels cause energy storage as fat and increase appetite.

How can I test myself for insulin resistance?

You can suspect insulin resistance with: a lot of abdominal fat (waist circumference >102 cm for men, >88 cm for women), dark skin patches or skin tags, PCOS or erectile dysfunction, family history of heart disease or type 2 diabetes, or fluid retention. A doctor can test blood values: fasting glucose (>5.5 mmol/l), triglycerides (>1.7 mmol/l), low HDL cholesterol.

How does intermittent fasting work for insulin resistance?

Intermittent fasting reduces the frequency of insulin spikes, which can improve insulin sensitivity. Studies show that 24-hour fasting periods in people with type 2 diabetes can improve insulin sensitivity to such an extent that medication use can sometimes be reduced or stopped.

What is prediabetes and why is it underestimated?

Prediabetes (fasting blood glucose between 5.6 and 6.9 mmol/l) is underestimated because insulin levels are often elevated for years before prediabetes is detected. This can contribute to high blood pressure, atherosclerosis, and cardiovascular disease, long before the diabetes diagnosis is made.