Type 2 diabetes is one of the most common chronic health conditions in the U.S. (a whopping 10.5% of the population has it)1—yet it is woefully misunderstood by most people. There are all kinds of misconceptions about what causes type 2 diabetes. Because of this, you might think you did something wrong if you get a type 2 diabetes diagnosis. But the truth is, the condition is the result of a combination of factors, some of which can be outside of your control. Ultimately, type 2 diabetes occurs when your body doesn’t use insulin properly. The good news is that there are lots of ways to change that. Keep reading to learn what really causes type 2 diabetes—and what you can do to prevent it.
What is type 2 diabetes?
In a nutshell, type 2 diabetes is a chronic disease that occurs when your pancreas doesn’t produce enough insulin (or doesn’t use it efficiently), which results in too much glucose (or sugar) circulating in your blood, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Over time, high blood sugar levels can cause problems with your immune, nervous, and circulatory systems. Worth noting: If your body has started having problems producing insulin and using glucose, but your blood sugar hasn’t yet risen to a concerning level, then you may be diagnosed with prediabetes.
So what’s the difference between type 1 and type 2 diabetes? Type 1 diabetes also occurs when there is too much glucose in the blood, but it’s an autoimmune condition, meaning the body attacks the insulin-producing cells in the pancreas.
What causes type 2 diabetes?
Experts don’t know exactly what causes type 2 diabetes, but there are several factors at play—some are within your control (think: getting enough exercise) while others are outside of your control (like genetics). Here are some possible causes:
Insulin resistance
The main culprit of type 2 diabetes, insulin resistance is when your body doesn’t use insulin efficiently, which leads to high blood sugar. Glucose is what your body uses for energy. But it has a lock on it, meaning it can’t get into your cells on its own; it needs insulin to do that (think of insulin as a key that opens the lock so glucose can enter).
Insulin resistance is when your key (insulin) doesn’t work as well as it should. Sometimes it unlocks, and sometimes you have to go through a series of acrobatic hand movements to get the lock to open. Since glucose isn’t getting into your cells consistently, it means there is extra circulating in your blood, increasing your blood glucose, or blood sugar, which may lead to type 2 diabetes.
There’s another thing that happens with insulin resistance. Your body can’t make enough insulin to compensate for the extra glucose. As a result, more glucose ends up circulating in your blood, which can damage your cells and lead to complications that affect your eyes, kidneys, and nerves, according to a 2019 study published in the journal Nature.2
Excess body fat
So what causes insulin resistance in the first place? The answer is complicated, and it doesn’t just happen overnight. But one of the main factors is excess body fat, which can cause inflammation throughout your body. That inflammation may then trigger a chain reaction that ultimately leads to insulin resistance and eventually type 2 diabetes, according to a 2015 study published in the journal Lipids in Health and Disease.3
It’s important to note that not all people with type 2 diabetes are considered clinically overweight, and not all people who carry excess weight have type 2 diabetes.
Your genes and how you grew up
Inheriting certain genes can increase your risk of developing type 2 diabetes. If you have one parent with type 2 diabetes, your risk increases by 40%, according to a 2015 study published in the journal Genes. If both parents have it, that risk jumps to 70%. And compared to the general population, you have a three-fold increased risk if you have a parent or sibling with type 2 diabetes.4