Understanding the Core Problem: Insulin and Blood Sugar

To understand what causes diabetes, it helps to first understand what’s happening inside the body.

When you eat carbohydrates (bread, rice, pasta, fruit, sugar, etc.), your digestive system breaks them down into glucose, which enters the bloodstream. Glucose is the body’s main fuel source, but it cannot effectively enter most cells without insulin.

Insulin is a hormone made by the pancreas (specifically, beta cells). It acts like a key that helps glucose move from the blood into the cells, where glucose is used to produce energy.

Diabetes develops when one or both of these problems occur:

Not enough insulin is produced (insulin deficiency), or
The body can’t use insulin properly (insulin resistance)

Both pathways cause glucose to build up in the bloodstream, leading to high blood sugar—the defining feature of diabetes.

What we don’t always know is why the pancreas stops producing enough insulin in one person, or why insulin resistance becomes severe in another. That’s where the different types of diabetes matter.

1) General Causes of Diabetes: What We Know (and What We Don’t)

At the most basic level, diabetes happens because blood sugar is not regulated properly—due to insulin deficiency, insulin resistance, or both. But the deeper cause is usually a mix of:

Genetics: family history can increase risk for many forms of diabetes
Immune system factors: especially in type 1 diabetes
Hormones: major factor in gestational diabetes
Body fat distribution: especially belly fat in type 2 diabetes
Lifestyle influences: inactivity, poor sleep, chronic stress, and dietary patterns
Age and life stage: risk changes across the lifespan
Other health conditions: PCOS, fatty liver, high blood pressure, abnormal lipids

So when someone says “no one knows what causes diabetes,” that’s only partly true.

We do understand the mechanisms (insulin resistance, beta cell failure, immune attack). What we can’t always pinpoint is the exact trigger that caused diabetes in one specific person.

2) Gestational Diabetes (GDM): The Role of Pregnancy Hormones

Gestational diabetes is diabetes diagnosed during pregnancy, typically in the second or third trimester. It happens because pregnancy causes major hormonal changes that affect insulin.

During pregnancy, the placenta produces hormones that help the baby grow. Some of these hormones can make the mother’s body less sensitive to insulin. This is a normal pregnancy process—but in some women, insulin resistance becomes strong enough that the pancreas can’t keep up with the increased demand.

In simple terms:

Pregnancy hormones increase insulin resistance
The pancreas must produce more insulin to compensate
If it can’t produce enough insulin, blood sugar rises → gestational diabetes
Why do only some women develop GDM?

That’s the big question. While the hormonal mechanism is clear, risk depends on factors like:

family history of diabetes
previous gestational diabetes
higher pre-pregnancy weight (especially central obesity)
older maternal age
PCOS or previous insulin resistance
certain ethnic backgrounds (risk varies by population)
history of having a large baby (macrosomia)

Many women with GDM feel confused because they “ate well” and “did everything right.” The truth is that pregnancy can reveal a vulnerability in glucose regulation that was already there—especially insulin resistance tendency.

Does GDM go away?

Often, blood sugar returns to normal after delivery. But gestational diabetes increases the risk of developing type 2 diabetes later, which is why postpartum follow-up and long-term lifestyle support are important.

3) Type 1 Diabetes: Autoimmune Attack on the Pancreas

Type 1 diabetes is very different from type 2.

In type 1 diabetes, the immune system mistakenly attacks the insulin-producing beta cells in the pancreas. Over time, the body loses the ability to make insulin. Without insulin, blood sugar rises and can become dangerous quickly.

What causes the immune system to attack beta cells?

We know the process is autoimmune, but we don’t fully know what triggers it in every case. Current evidence suggests a combination of:

genetic susceptibility (certain genes increase risk)
environmental triggers (possibly infections or other exposures)
immune system misfiring (loss of tolerance to beta cells)

Some researchers have explored links with viral infections, early-life immune development, and other factors—but no single trigger explains all cases universally.

Key point:

Type 1 diabetes is not caused by eating sugar, not caused by laziness, and not caused by “bad lifestyle choices.” It is an immune-mediated condition that requires insulin treatment.

4) Type 2 Diabetes and Prediabetes: Insulin Resistance + Beta Cell Strain

Prediabetes is often a warning stage before type 2 diabetes. In prediabetes, blood sugar is higher than normal but not yet in the diabetes range. Many people can reverse or improve prediabetes with lifestyle changes—but it can progress to type 2 if the underlying problem worsens.

What’s happening in type 2 diabetes?

Type 2 diabetes typically develops in stages:

Insulin resistance increases
Cells respond less to insulin, so glucose has trouble entering cells.
The pancreas compensates
The pancreas produces extra insulin to keep blood sugar in check.
Blood sugar begins to rise
Over time, insulin resistance increases and the pancreas can’t keep up.
Beta cells become strained
Eventually, insulin production may decline as beta cells lose function.

The liver also plays a role. In insulin resistance, the liver may release too much glucose into the bloodstream, especially overnight and between meals.

Risk factors strongly linked with type 2 diabetes

While we may not know the single “cause” in one individual, the strongest evidence links type 2 diabetes with:

Age: risk increases with age, though younger cases are rising
Family history: genetics matter
Ethnicity: risk differs across groups due to genetics + environment
Inactivity: less muscle activity reduces glucose disposal
Overweight/obesity: especially visceral fat (belly fat)
Sleep problems: poor sleep and sleep apnea are associated with insulin resistance
Chronic stress: affects hormones and behaviors, and can worsen glucose regulation
Unhealthy dietary patterns: high refined carbs, sugary drinks, and ultra-processed foods can contribute to weight gain and insulin resistance
But why do some obese people never get diabetes?

This is an important and common question—and it’s exactly why diabetes cannot be reduced to one cause.

Some people carry extra weight but:

store more fat under the skin instead of around organs
maintain better insulin sensitivity
have stronger beta-cell function
are more physically active or have more muscle mass
have different genetic risk

Meanwhile, some people develop type 2 diabetes at a lower body weight due to genetics, fat distribution, and other metabolic factors. That’s why individualized screening and prevention matter.

5) Common Rumors and Myths About Diabetes

When people don’t have clear explanations, myths spread quickly. Let’s correct the biggest ones.

Myth 1: “Diabetes is contagious.”

Diabetes is not contagious. You cannot catch diabetes from another person. Some forms have genetic risk, but it is not passed like a virus.

Myth 2: “Eating sugar causes diabetes.”

Eating sugar does not directly “cause” diabetes the way a germ causes an infection. However:

excessive sugar intake can promote weight gain in some people
sugary drinks can raise blood sugar rapidly and contribute to insulin resistance
chronic high-calorie diets can worsen metabolic health

So sugar is not the direct cause, but heavy sugar intake can contribute to the conditions that raise risk—especially for type 2 diabetes.

Myth 3: “Stress causes diabetes.”

Stress alone isn’t proven to directly cause diabetes, but it can:

worsen blood sugar in people who already have diabetes
promote behaviors that increase risk (poor sleep, overeating, inactivity)
raise cortisol, which can increase glucose levels

Stress is best viewed as a risk amplifier, not a single cause.

Myth 4: “Only overweight people get diabetes.”

False. Weight is a major risk factor for type 2 diabetes, but:

type 1 diabetes can occur at any weight
type 2 diabetes can occur in people who are not overweight
fat distribution and genetics matter
What You Can Do: Practical Prevention and Risk Reduction

Even though no one can control genetics or pregnancy hormones, there are powerful steps that reduce risk and improve outcomes:

1) Keep blood sugar more stable
Reduce sugary drinks and refined carbs
Build meals with protein + fiber + healthy fats
Choose whole-food carbs (beans, lentils, vegetables, oats, fruit)
2) Move your body consistently
Walking after meals helps glucose control
Strength training increases muscle glucose uptake
Even 10–20 minutes daily makes a difference over time
3) Manage body weight if needed

Modest weight loss can significantly improve insulin sensitivity for many people with prediabetes or type 2 diabetes.

4) Improve sleep

Poor sleep and sleep apnea are strongly linked with insulin resistance. Treating sleep issues can improve glucose control.

5) Get screened early

Prediabetes often has no symptoms. Early detection allows early action.

Final Thoughts

We know a lot about what happens inside the body in diabetes:

type 1: autoimmune destruction of insulin-producing cells
type 2: insulin resistance plus beta-cell strain
gestational: pregnancy hormones increase insulin resistance

But we don’t always know the exact trigger for each person, which is why diabetes can feel mysterious and frustrating.

The best approach is not to chase rumors or blame yourself—it’s to focus on what you can control:

consistent healthy eating
regular movement
weight management if needed
good sleep and stress management
routine medical follow-up