Prediabetes: The Silent Precursor - Why Even Lean People Can Be Affected.

Table of Contents:

What is Prediabetes?

Prediabetes is a serious health condition where blood sugar levels are higher than normal but not yet high enough to be diagnosed as type 2 diabetes. Medically speaking, it involves impaired glucose tolerance or abnormal fasting glucose – precursors to full-blown diabetes.

"Prediabetes is an important warning sign from the body that we should not ignore. About 90% of people with prediabetes don't know they have it – a disturbing statistic that underscores the importance of education on this topic." - Prof. Dr. Maria Schulze, Diabetologist at the University Hospital Hamburg

According to current data from the Robert Koch Institute, approximately 7.5 million people in Germany are affected by prediabetes. Without intervention, 5-10% of those affected develop overt type 2 diabetes each year. The good news: this development is not inevitable. Early detection and lifestyle changes can stop or even reverse the progression.

Insulin Resistance: The Core of the Problem

Behind prediabetes, in most cases, lies a fundamental mechanism: insulin resistance. It is the physiological process underlying the disturbed metabolism – long before measurable blood sugar elevations appear.

What is Insulin Resistance?

Insulin is a vital hormone produced by the pancreas. Its main task is to signal to the body's cells that they should absorb glucose (sugar) from the blood. In insulin resistance, these cells – especially in muscles, fat, and the liver – become less sensitive to this signal.

"Imagine insulin as a key that opens the cell door to let glucose in. With insulin resistance, the lock is changed so the key no longer fits optimally. The body then produces more keys (insulin) to still open the door." - Dr. Michael Schmidt, Endocrinologist

The Difference Between Insulin Resistance and Prediabetes

Although closely related, insulin resistance and prediabetes are not the same:

Insulin Resistance:

A physiological state, not a clinical diagnosis
Can exist for years before blood sugar elevations
Often no direct symptoms
Primarily affects the cellular response to insulin

Prediabetes:

A clinical diagnosis with defined thresholds
Detectable by standardized blood sugar tests
Result of long-term insulin resistance when the pancreas can no longer fully compensate for the increased insulin demand

The development typically proceeds in the following phases:

Beginning insulin resistance with normal blood sugar levels due to increased insulin production
Progressive insulin resistance with occasional blood sugar spikes
Prediabetes with measurable blood sugar elevations
Exhaustion of insulin-producing beta cells and development of type 2 diabetes

A Yale University study showed that lean people with insulin resistance had elevated fat content in their liver and muscles – similar to obese individuals. This illustrates why even externally lean people can develop metabolic disorders.

The Lean Myth: Why Thin People Are Also Affected

One of the most dangerous misconceptions about prediabetes is the assumption that only overweight people can be affected. Science paints a more nuanced picture:

Metabolically Unhealthy Normal Weight: A study in the Journal of Clinical Endocrinology & Metabolism showed that up to 30% of normal-weight adults exhibit metabolic disorders associated with an increased risk of diabetes.
Fat Distribution Rather Than Total Weight: Not only body weight but also the distribution of body fat is crucial. Visceral fat (abdominal fat surrounding internal organs) poses a higher risk than subcutaneous fat.
Genetic Factors: Certain genetic variants can increase the risk of insulin resistance, regardless of body weight.
TOFI Phenomenon (Thin Outside, Fat Inside): Externally lean people can have an unfavorable ratio of fat to muscle mass, with increased fat storage in organs such as the liver.

"In my coaching, I regularly see lean patients with prediabetes. The term 'lean but metabolically obese' aptly describes this phenomenon. These individuals have normal BMI values, but their metabolic values are similar to those of overweight people." -

Warning Signs: You Should Take These Signs Seriously:

Prediabetes and early insulin resistance are often asymptomatic, which makes them particularly insidious. Nevertheless, there are subtle signs that may indicate an increased risk:

Unusual fatigue, especially after carbohydrate-rich meals
Increased thirst and more frequent urination
Slow wound healing
Dark skin patches in body folds (Acanthosis nigricans)
Elevated blood pressure and abnormal cholesterol levels
Recurrent fungal infections
Strong cravings, especially for sweets
In women: Irregular cycles or PCOS (Polycystic Ovary Syndrome)

If you notice one or more of these symptoms, it is advisable to talk to your doctor – regardless of your body weight or age.

Diagnosis: How Prediabetes and Insulin Resistance Are Detected

Standard Tests for Prediabetes

Prediabetes is diagnosed through various blood tests:

1. Fasting Plasma Glucose (FPG):

Normal: below 100 mg/dL (5.6 mmol/L)
Prediabetes: 100-125 mg/dL (5.6-6.9 mmol/L)
Diabetes: 126 mg/dL (7.0 mmol/L) or higher

2. Oral Glucose Tolerance Test (OGTT):

Normal: below 140 mg/dL (7.8 mmol/L) after 2 hours
Prediabetes: 140-199 mg/dL (7.8-11.0 mmol/L) after 2 hours
Diabetes: 200 mg/dL (11.1 mmol/L) or higher after 2 hours

3. HbA1c (Long-term Blood Sugar):

Normal: below 5.7%
Prediabetes: 5.7-6.4%
Diabetes: 6.5% or higher

Measuring Insulin Resistance

Insulin resistance is measured by more specific tests, which are not part of routine diagnostics but can be performed if suspected:

1. HOMA-IR (Homeostasis Model Assessment of Insulin Resistance):

A mathematical model that combines fasting insulin and fasting glucose
Formula: HOMA-IR = (Fasting insulin [µU/ml] × Fasting glucose [mg/dl]) ÷ 405
Interpretation:
- < 1.0: Normal
- 1.0-1.9: Moderate insulin resistance
- 2.0: Significant insulin resistance

2. QUICKI (Quantitative Insulin Sensitivity Check Index):

An alternative calculation for insulin sensitivity
Formula: QUICKI = 1 ÷ (log(Fasting insulin [µU/ml]) + log(Fasting glucose [mg/dl]))
Higher values mean better insulin sensitivity

3. Insulin Tolerance Test:

A dynamic test where insulin is injected and the subsequent blood sugar drop is measured
Slow drop indicates insulin resistance

4. Glucose Clamp Technique:

The gold standard for research purposes
Precisely measures how much glucose is needed to maintain stable blood sugar levels during constant insulin infusion
Complex procedure mainly used in studies

Experts recommend regular screening for prediabetes from age 35, especially if risk factors are present. If the findings are normal, the examination should be repeated every three years.

"The OGTT with simultaneous insulin measurement is particularly informative. An excessive insulin surge with a normal glucose curve can detect early insulin resistance long before blood sugar changes appear." - Prof. Dr. Laura Fischer, Diabetologist

Dietary Changes: The Key to Reversal

Diet plays a crucial role in the management of prediabetes and insulin resistance. Scientific studies show that targeted dietary changes can reverse the condition in many cases.

Basic Principles of an Insulin Sensitivity-Promoting Diet:

1. Carbohydrate Quality Over Quantity

Whole grains instead of refined carbohydrates
Fiber-rich foods to slow glucose absorption
Low glycemic index and low glycemic load

2. Healthy Fats

Omega-3 fatty acids from fish, flaxseed, and walnuts
Olive oil and avocados as sources of monounsaturated fatty acids
Reduction of saturated and trans fats

3. Protein Sources

Lean poultry and fish
Legumes and nuts
Fermented dairy products

4. Micronutrient-Rich Foods

Chromium, magnesium, and vitamin D for better insulin sensitivity
Antioxidants from colorful vegetables and fruits

5. Pay Attention to Meal Order

Start meals with vegetables and protein, then carbohydrates
This order has been shown to reduce post-meal blood sugar spikes

Practical Implementation

Example of a Daily Plan:

Breakfast: Oatmeal with berries, flaxseed, and unsweetened yogurt Snack: Handful of almonds and an apple Lunch: Grilled chicken fillet with quinoa and plenty of colorful vegetables Snack: Vegetable sticks with hummus Dinner: Salmon with broccoli and sweet potato salad

In my own case, I have found that meal timing is as important as its composition. Maintaining regular meal times and an early dinner (ideally 3-4 hours before bedtime) have a positive impact on my blood sugar levels and insulin sensitivity.

Exercise as an Effective Therapy

Physical activity is a powerful tool against prediabetes and insulin resistance – regardless of initial weight. Exercise improves insulin sensitivity immediately and long-term.

Mechanism of Action:

Short-term Effects: Muscle contraction increases glucose uptake into cells, even without insulin
Long-term Effects: Building muscle mass, which serves as a "glucose reservoir"
Metabolic Improvements: Reduction of visceral fat, better mitochondrial function
Molecular Adaptations: Increase in GLUT4 transporter proteins, which are responsible for glucose transport into cells

Recommended Forms of Exercise:

Combined program of:

150 minutes of moderate aerobic activity per week (e.g., brisk walking, swimming)
2-3 strength training sessions per week
Break up long periods of sitting at least every 30 minutes

"High-intensity interval training (HIIT) is particularly effective, achieving similar or better metabolic effects in a shorter time than moderate endurance training. For insulin resistance, the combination of HIIT and strength training seems optimal." - Dr. Anna Müller, Sports Physician

In my personal training plan, I have found that a 10-minute strength training session before breakfast stabilizes my blood sugar levels for the entire morning. This phenomenon is scientifically proven and is known as "exercise snacking."

Patient Experience: "I Had No Idea"

Julia M., 42:

"As a lean person with an active lifestyle, I never thought I could be at risk for diabetes. During a routine check-up, my elevated blood sugar level was discovered. A subsequent HOMA-IR test confirmed significant insulin resistance. In retrospect, I realize that the occasional energy dips after lunch, increasing exhaustion, and my insatiable craving for sweets were warning signs.

After my diagnosis eight months ago, I changed my diet: fewer processed foods, more vegetables, and whole grains. I also make sure to eat regularly and reduce my stress. At my last check-up, my values were back in the normal range. My HOMA-IR value improved from 2.8 to 1.1. This experience has changed my life for the better."

Frequently Asked Questions

Q: What is the difference between prediabetes and insulin resistance?
A: Insulin resistance is the physiological process where body cells become less sensitive to insulin. Prediabetes is the clinical diagnosis given when blood sugar levels are elevated but have not yet reached the diabetes threshold. Insulin resistance is typically the cause of prediabetes but can exist for a long time before measurable blood sugar changes occur.

Q: Can prediabetes be completely cured?
A: Yes, in many cases, prediabetes can be reversed through lifestyle changes. Studies show that about 50-70% of cases can be normalized through targeted measures.

Q: Do I need medication for prediabetes or insulin resistance?
A: Primarily, lifestyle changes are recommended. In certain cases, your doctor may prescribe metformin, especially if additional risk factors are present or if lifestyle changes alone are not sufficient.

Q: How often should I have my blood sugar checked?
A: For diagnosed prediabetes, experts recommend annual blood sugar checks. Your doctor may advise more frequent checks depending on your individual risk profile.

Q: Can I still eat fruit as a person with prediabetes?
A: Yes, fruit is an important part of a healthy diet. However, it is important to choose the right types (preferably berries and apples instead of very sweet fruits) and to control portion sizes.

Q: Is there a link between sleep deprivation and insulin resistance?
A: Yes, scientific studies show that chronic sleep deprivation (less than 6 hours per night) increases the risk of insulin resistance and prediabetes. Even one night of 4 hours of sleep can reduce insulin sensitivity by up to 25%.

References

American Diabetes Association. "Standards of Medical Care in Diabetes—2024." Diabetes Care, 2024.
Tabák AG, et al. "Prediabetes: a high-risk state for diabetes development." The Lancet, 2023.
Robert Koch-Institut. "Diabetes in Deutschland – Bericht der Nationalen Diabetes-Surveillance 2024."
Eckel RH, et al. "Metabolically healthy normal weight: an oxymoron?" Journal of Clinical Endocrinology & Metabolism, 2022.
Lean ME, et al. "Primary care-led weight management for remission of type 2 diabetes (DiRECT)." The Lancet, 2023.
Colberg SR, et al. "Physical Activity/Exercise and Diabetes: A Position Statement of the American Diabetes Association." Diabetes Care, 2024.
Harvard T.H. Chan School of Public Health. "The Nutrition Source: Preventing Diabetes." 2024.
Deutsche Diabetes Gesellschaft. "Praxisempfehlungen 2024/2025."
Wallace TM, et al. "Use and abuse of HOMA modeling." Diabetes Care, 2023.
Petersen MC, Shulman GI. "Mechanisms of Insulin Action and Insulin Resistance." Physiological Reviews, 2022.
Srikanthan P, Karlamangla AS. "Relative Muscle Mass Is Inversely Associated with Insulin Resistance and Prediabetes." Journal of Clinical Endocrinology & Metabolism, 2023.
Thomas DD, et al. "Timing of Daily Meal Timing Associates with the Timing of Glucose Peaks in Individuals Tracked with Continuous Glucose Monitoring." Cell Metabolism, 2023.

Prediabetes Risk Test: Could You Be Affected?

Last updated: March 7, 2025

Introduction

This self-test can help you assess your personal risk for prediabetes. It does not replace a medical diagnosis, but it can be an initial indication of whether you should discuss this topic with your doctor.

The test is based on scientifically recognized risk factors and was developed in accordance with established screening instruments such as the German Diabetes Risk Test (GDRS) and the ADA Risk Test.

Instructions

Answer all questions honestly and add up the points. The total result will give you an initial assessment of your personal risk.

Part 1: General Risk Factors

1. Age

Under 35 years (0 points)
35-44 years (1 point)
45-54 years (2 points)
55-64 years (3 points)
65 years or older (4 points)

2. Sex

Male (1 point)
Female (0 points)

3. Family History

Parents, siblings, or children with Type 2 diabetes (5 points)
Grandparents, aunts, uncles, or cousins with Type 2 diabetes (2 points)
No known cases of diabetes in the family (0 points)

4. Ethnic Background

Caucasian/European descent (0 points)
African, Latin American, Southeast Asian, Pacific Islander descent (2 points)

5. High Blood Pressure

Have you ever been treated for high blood pressure or are you taking blood pressure-lowering medication? (2 points)
No (0 points)

6. Cholesterol Levels

Have you been diagnosed with elevated cholesterol levels (LDL) or low HDL levels? (2 points)
No or not known (0 points)

Part 2: Physical Factors

7. Body Mass Index (BMI)

Under 18.5 (0 points)
18.5-24.9 (0 points)
25-29.9 (2 points)
30-34.9 (3 points)
35 or higher (5 points)

BMI calculation: Weight (kg) ÷ [Height (m)]²

8. Waist Circumference

Measure your waist circumference at the level of the navel while standing:

Men:

Under 94 cm (0 points)
94-101 cm (3 points)
Over 101 cm (5 points)

Women:

Under 80 cm (0 points)
80-87 cm (3 points)
Over 87 cm (5 points)

9. Body Fat Distribution

Do you carry more weight around your waist (apple-shaped)? (2 points)
Do you carry more weight on your hips and thighs (pear-shaped)? (0 points)
Even distribution or not sure (1 point)

Part 3: Lifestyle

10. Physical Activity

Less than 30 minutes of moderate activity per week (5 points)
30-149 minutes of moderate activity per week (2 points)
150 minutes or more of moderate activity per week (0 points)

11. Eating Habits

Daily consumption of sugary drinks or sweets (2 points)
Less than 2 servings of fruits and vegetables daily (2 points)
More than 3 servings of processed foods daily (2 points)
None of the above (0 points)

12. Sleep Quality

Average of less than 6 hours of sleep per night (2 points)
Regular sleep problems or shift work (1 point)
Good sleep quality with 7-9 hours per night (0 points)

13. Stress Level

Chronic high stress (2 points)
Occasional stress (1 point)
Low stress level (0 points)

Part 4: Symptoms and History

14. Have you ever had elevated blood sugar levels during pregnancy (gestational diabetes)?

Yes (4 points)
No (0 points)
Not applicable (0 points)

15. Have you ever been diagnosed with Polycystic Ovary Syndrome (PCOS)?

Yes (2 points)
No (0 points)
Not applicable (0 points)

16. Do you notice one or more of the following symptoms? (1 point each, maximum 5 points)

Unusual fatigue, especially after meals
Increased thirst
More frequent urination
Slow wound healing
Recurrent yeast infections
Dark skin changes in body folds (armpits, neck)
Tingling or numbness in hands or feet

Evaluation

0-7 points: Low risk Based on your answers, your risk of prediabetes appears to be low. Maintain your healthy lifestyle and have your blood sugar checked during routine examinations.

8-14 points: Medium risk You have some risk factors for prediabetes. Discuss the possibility of a blood sugar test with your doctor during your next routine check-up. Small changes to your lifestyle could be helpful.

15-24 points: Increased risk Your risk of prediabetes is increased. It is recommended to consult a doctor promptly and have a blood sugar test performed. Targeted measures may help you reduce your risk.

25 points or more: High risk You have several significant risk factors for prediabetes or type 2 diabetes. It is strongly recommended to consult a doctor as soon as possible and have a comprehensive blood sugar test performed.

Important note

This test is for initial guidance only and cannot replace a medical diagnosis. Even with a low risk, prediabetes may be present, especially if you notice unusual symptoms.

The only sure way to diagnose prediabetes is a blood test at the doctor: fasting blood sugar, oral glucose tolerance test (OGTT) or HbA1c test.

Disclaimer: This self-test is for informational purposes only and does not replace medical advice, diagnosis or treatment by qualified health professionals. Always consult your doctor if you have health concerns.

About the author

Our founder Fabienne Geiger completed advanced training in sustainable nutrition at Harvard Medical School and the course "Child Nutrition and Cooking" at Stanford University. As a certified nutritional consultant, she regularly shares her expertise on our blog.

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Prediabetes: The Silent Harbinger - Why Even Lean People Can Be Affected