What Are the Causes and Risk Factors of Type 2 Diabetes?

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Diet, lifestyle, and weight are just three of many factors that affect type 2 diabetes risk.Canva; Everyday Health
More than 34 million Americans were living with diabetes in 2018 — that’s roughly 10 percent of the population, according to the American Diabetes Association (ADA).

And even more people have prediabetes, which means they have blood sugar levels that are higher than normal but not quite high enough to qualify as type 2 diabetes, according to the Mayo Clinic.

In the face of these growing numbers, it’s important to know whether you’re at risk and, if so, what you can do to prevent type 2 diabetes, which is the most common form of diabetes.

What Causes Type 2 Diabetes?

You may have heard that unhealthy eating habits or being overweight means you’ll develop type 2 diabetes. While those factors increase your risk, the cause of type 2 diabetes is much more complex than that.

“Type 2 diabetes has a strong genetic component,” says Leann Olansky, MD, a board-certified endocrinologist at Cleveland Clinic in Ohio. But daily habits matter, too. “If you choose a healthy lifestyle you may really be able to avoid diabetes or put it way off,” Dr. Olansky says.

You can still be diagnosed with diabetes without the genetic component, says John P. Martin, MD, the codirector of the Diabetes Complete Care Program at Kaiser Permanente in Los Angeles. “It's not like not having the genetic tendency is going to protect you,” he says. “You can still get it if your diet and your weight management and your self-care isn't where it needs to be.”

What Are the Risk Factors for Type 2 Diabetes?

Some risk factors you may have some control over. “It looks like type 2 diabetes is exploding worldwide, but the genetics haven't changed,” Olansky says. “What's changed is the way people are eating and living.”

According to the Mayo Clinic and the Centers for Disease Control and Prevention (CDC), the following increase your risk of type 2 diabetes:

  • Overweight or obesity Being overweight can lead to insulin resistance, which can then lead to type 2 diabetes. It’s not just the extra weight, but where you carry it that matters. Extra fat in the belly area, which is called visceral fat, is linked to insulin resistance and type 2 diabetes. One reason is that visceral fat secretes retinol-binding protein 4, which increases insulin resistance, according to Diabetes.co.uk.

  • Activity levels Being physically active less than three times a week increases your risk.

  • Cholesterol levels Low levels of high-density lipoprotein (HDL) cholesterol are linked to insulin resistance and may contribute to an increased risk of type 2 diabetes. Levels less than 40 milligrams per deciliter (mg/dL) in a man and less than 50 mg/dL in a woman are considered low, Olansky says.
  • High levels of triglycerides As with low HDL cholesterol, high triglycerides, which are a kind of fat found in your blood, may indicate insulin resistance and be linked to an elevated type 2 diabetes risk. Levels of less than 150 mg/dL are considered normal, according to Harvard Health Publishing.

    “Anything above that probably shows some risk,” Olansky says. Again, high levels of triglycerides or low levels of HDL cholesterol don’t necessarily indicate you have diabetes, but they are pieces of the risk puzzle and point to your metabolic state, Dr. Martin says.
  • Smoking “Smoking is another thing that can increase insulin resistance and can increase the likelihood that you'll manifest diabetes,” Olansky says.

There are some risk factors you have less control over, such as:

  • Family history There is a strong genetic link to type 2 diabetes. If a parent or sibling has type 2 diabetes, you are at increased risk. “If you have family members with type 2 diabetes, then you probably have the genetic risk,” Olansky says. “And if you've got them on both your mother's and your father's side, you have even higher likelihood because you're going to get a combination of both of those.” If your mother, father, or both have type 2 diabetes, your risk increases two to four times, according to a 2017 review published in Current Diabetes Reviews.

  • Race and ethnicity Type 2 diabetes is more common in certain ethnic and racial groups, including African Americans, Alaska Natives, American Indians, Asian Americans, Hispanics/Latinos, Native Hawaiians, and Pacific Islanders. According to a review published February 2019 in Diabetes/Metabolism Research and Reviews that considered the reasons for the increased risk among Hispanics, it could be due to lower income, decreased access to education and healthcare, and a genetic susceptibility to insulin resistance and obesity.

  • Age People older than 45 are at increased risk. Previous research notes this is because of increasing insulin resistance and because the pancreas’s hormone release function can become impaired as we age.

  • Health history If you’ve had gestational diabetes or had a baby who weighed more than 9 pounds at birth, you are at increased risk. Having nonalcoholic fatty liver disease and polycystic ovary syndrome (PCOS) are also contributing factors.
  • Dark skin in the armpits or on the neck This is called acanthosis nigricans and indicates insulin resistance. It doesn’t always mean you have diabetes, but it can be a sign. “It is a marker that tells us that patients have insulin resistance,” Olansky says. Having acanthosis nigricans means you’re twice as likely to have diabetes as someone without the skin condition, Martin says.

Martin adds that there are socioeconomic factors that come into play as well. “You can't control the socioeconomic stressors you have in your life that might limit your ability to buy healthy foods and buy them cheaply,” he says. “There are not always resources to overcome those socioeconomic health barriers.”

How Insulin Influences Type 2 Diabetes Risk

Insulin, a hormone that’s produced by the pancreas, is in charge of allowing sugar (glucose) to move from the bloodstream to the cells.

In type 2 diabetes, the glucose doesn’t move into the cells effectively (insulin resistance) and instead builds up in the bloodstream, raising blood sugar levels. The high blood sugar levels tells the pancreas to continue making more insulin, according to the CDC.

If you have insulin resistance it doesn’t necessarily mean you have diabetes, but it can lead to weight gain and a type 2 diabetes diagnosis if your blood sugar remains high.

How Can I Help Prevent Type 2 Diabetes?

If you have a family history of type 2 diabetes or come from a racial or ethnic group that’s at high risk, you’re not destined to develop diabetes. “If I had to weigh it, I would say diet and self-care probably trumps genetics,” Martin says.

Research has shown that more than 90 percent of type 2 diabetes cases are potentially preventable, as long as you follow a healthy diet, have a BMI of 25 or lower, exercise at least 30 minutes a day, avoid smoking, and limit alcohol consumption.

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), you can prevent or delay type 2 diabetes in these ways:

  • Lose weight and maintain a healthy weight. “The most important thing is weight management,” Martin says. Losing weight has been shown to improve blood sugar control, and specifically resulted in a 0.25 to 2.9 percent decrease in A1C levels (a marker of blood sugar) after three to six months of diet changes, according to a previous article published in the International Journal of Clinical Practice.

  • Exercise more frequently. Aim to move for 30 minutes, five days a week. “Brisk walking is adequate — you don't have to be a marathon runner,” Olansky says. Walking at least 30 minutes a day can lower the risk of type 2 diabetes by 50 percent, according to a previous review published in the World Journal of Diabetes.

    It’s a good idea to incorporate strength training as well — it’s been shown to lead to improvements in HbA1c, insulin sensitivity, and fasting plasma glucose, according to a systematic review and meta-analysis published in the International Journal of Behavioral Nutrition and Physical Activity.

  • Eat a healthy, balanced diet. Try reducing your portion size to cut the number of calories you eat each day. Also try to avoid high-calorie and high-fat foods, which can contribute to weight gain. “You want to limit the amount of saturated fat and carbohydrates, particularly simple sugars,” Olansky says. Simple sugars, such as glucose and fructose, can be dangerous because they can lead to blood sugar spikes and increased insulin secretion, according to the Harvard T.H. Chan School of Public Health.

The lifestyle practices above were found to lower the incidence of type 2 diabetes by 57 percent (even more for people who sustained a weight loss of 5 percent or greater for two or three years), according to a previous analysis.

Martin says it’s also important to stay in contact with your physician if you’re at risk and to educate yourself about diabetes. “The more you know, the more power you have so you can take control of your life,” he says.


There are factors within your control and factors out of your control that contribute to your risk of type 2 diabetes. “The relationship can be quite complex, but the reality is that you can have a strong genetic component, but mitigating lifestyle risk factors such as obesity, poor diet, and lack of exercise can help prevent the transition into a diabetes full diagnosis,” Martin says. “It's not easy. It's a lot of work. It's not always going to go perfectly, and there will be times when you may fall off in terms of self-care, but the important thing is that you get back on.”

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