- Type 2 diabetes is caused by insulin resistance that develops over time.
- The main risk factors for type 2 diabetes include being obese, lacking physical activity, getting older, having a family history of diabetes, and belonging to certain races or ethnicities.
- To prevent type 2 diabetes, you can lose weight, exercise more, and adjust your diet – here’s how.
- This article was medically reviewed by Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine.
- Visit Insider’s Health Reference library for more advice.
Diabetes affects more than 34 million Americans, or about 10% of the US population. There are two types of diabetes – and 90% to 95% of those with diabetes have type 2.
Type 2 diabetes is closely associated with obesity and is most common in people over the age of 45, although anyone can develop it. Here’s what causes type 2 diabetes, the major risk factors, and how you can prevent it.
What causes type 2 diabetes?
Type 2 diabetes is caused by insulin resistance, which is when the body can’t use insulin properly. Insulin is a hormone produced in the pancreas, a gland located near the stomach. This hormone regulates the process of converting the sugar from food into fuel for your body.
When you have insulin resistance, excess blood sugar, in the form of glucose, builds in your body and deprives you of energy from the food you eat.
“The pancreas can still create insulin, it just doesn’t work as well as it should, meaning sugar gets stuck in the blood instead of the insulin moving it into the cells of the body for energy,” says Stephanie Redmond, a doctor of pharmacy and co-founder of Diabetes Doctor Supplements.
Insulin resistance first develops in people with prediabetes. One-third of Americans have prediabetes and up to 70% of those people will progress to type 2.
Unfortunately, many people with prediabetes don’t know it because they have no symptoms, so regular checkups – including blood work to check your blood sugar levels – is important.
The Centres for Disease Control and Prevention (CDC) also maintains a risk assessment tool for people concerned about their risk for prediabetes.
There are many proven factors that can increase your risk for type 2 diabetes:
Being overweight or obese vastly increases the risk for type 2 diabetes. In fact, research shows 80% to 85% of the risk of developing type 2 diabetes is controlled by obesity.
Not getting enough exercise or movement also increases the risk for type 2 diabetes.
Conversely, exercising for 30 minutes daily can reduce the risk of developing diabetes by up to 58% when combined with dietary changes. That’s because during exercise your muscles use more blood sugar for fuels, reducing your blood sugar levels.
Diabetes is most common in people over 45. In fact, about 25% of Americans over 65 have diabetes, and nearly all of that figure has type 2.
That’s because insulin resistance increases with age, at the same time that the pancreas begins losing function, both of which can contribute to the development of type 2 diabetes.
Although type 2 diabetes is largely caused by obesity and a sedentary lifestyle, genetics is also an important risk factor. For example, having a parent with type 2 diabetes increases your risk for the condition by 2 to 4 times.
“My favourite saying about type 2 diabetes is that genetics loaded the gun, and lifestyle pulls the trigger,” says Redmond.
Read more about whether type 2 diabetes is genetic, and what to do if it runs in your family.
Race and ethnicity
Non-white Americans are more likely to develop type 2 diabetes. According to the American Diabetes Association, type 2 diabetes occurs in:
- 7.5% of non-hispanic white Americans
- 9.2% of Asian Americans
- 11.7% of non-Hispanic blacks
- 12.5% of Hispanics
- 14.7% of American Indians
A 2018 study looking at diabetes rates in Black Americans found that biological differences, including a body type that was more likely to have fat around the abdomen, accounted for most of the increased risk. But there are also socioeconomic risk factors: minorities may have less access to affordable health care or quality food options.
“Why these groups are more at risk is a complex question with no simple answer. For the most part, it’s related to both environmental and genetic factors,” says the Food and Drug Administration (FDA).
How to prevent type 2 diabetes
Even if you have risk factors for type 2 diabetes, you can prevent the disease and reverse it during the initial stages of insulin resistance and prediabetes. In fact, researchers estimate that 90% of type 2 diabetes cases in the US can be prevented.
“The key is to act early so you can prevent the pancreas from wearing out and getting damaged,” Redmond says.
For example, people who participate in lifestyle change programs backed by the CDC – including exercise and weight loss – can reduce their risk of type 2 diabetes by 58%. For people over 60, risk drops by 70%.
Here’s what you can do to prevent type 2 diabetes if you’re at risk:
- Lose weight. Dropping 7% to 10% of your body weight can reduce your risk for developing type 2 diabetes by 50%. Follow our guide for how to lose weight and talk to your doctor about what’s right for you.
- Exercise. Even moderate exercise, such as walking briskly for 30 minutes every day, can reduce your risk of developing type 2 diabetes by 30%.
- Stop smoking. Cigarette smokers are twice as likely to develop type 2 diabetes.
- Avoid excessive drinking. Heavy alcohol consumption can increase risk for type 2 diabetes, although moderate alcohol consumption may reduce risk by improving insulin effectiveness.
- Adjust your diet.Eating whole-grain foods and avoiding sugary, processed snacks can help regulate your blood sugar levels.
Preventative care and regular physicals are also important, since most people discover they have elevated blood sugars during routine blood work.
“This is why regular annual screenings are so important, to make sure if you have no symptoms we can still flag a higher than normal blood sugar and take action early,” Redmond says.
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