Causes and Risk Factors of Type 2 Diabetes

Type 2 diabetes, formerly known as adult-onset diabetes, accounts for up to 95% of diabetes cases and is mostly the result of obesity and a lack of exercise. However, there are other causes and risk factors that contribute to this form of diabetes.

This article explains what type 2 diabetes is and lists the seven common factors that can increase the risk of a disease that currently affects over 34 million adults and children in the United States.

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What Is Type 2 Diabetes?

Type 2 diabetes is a type of diabetes characterized by high blood glucose (sugar), insulin resistance, and a relative lack of insulin.

Glucose is the body's main form of energy, and insulin is the hormone produced by the pancreas that helps regulate glucose levels in the blood.

When insulin levels are low and/or the body fails to respond to the effects of insulin (insulin resistance), blood sugar levels can increase out of control. Over time, persistently high glucose levels, referred to as hyperglycemia, can damage blood vessels, nerves, kidneys, eyes, skin, brain, and other organs.

Type 2 diabetes is generally considered to be a lifestyle disease, but family history and genetics also play a major role in its development.

Insulin helps transport glucose from the bloodstream with the help of glucose transporters.

Lifestyle Risk Factors

While certain people are predisposed to type 2 diabetes due to their genetics, lifestyle plays the predominant role in the onset of the disease.

In short, having a genetic disposition for type 2 diabetes does not mean you will get it. The choices you make with respect to diet and exercise can ultimately determine if you get the disease or not.

Diet, Exercise, and Obesity

The number one risk factor for type 2 diabetes is being overweight or obese. A person is considered overweight when their body mass index (BMI) is over 25 and obese when their BMI is over 30. Today, over 140 million adults and over 14 million children in the United States have obesity.

The main symptom of obesity is excessive body fat, which increases the level of fatty acids in the blood. As these fats accumulate in the liver, the function of the liver becomes increasingly impaired. And, one of its main functions is the production and storage of glucose.

Obesity triggers the onset of insulin resistance which, in turn, contributes to the onset of type 2 diabetes.

Risk factors for obesity and being overweight include:

Body Mass Index

BMI is the most commonly used measure to correlate weight and height. It uses weight and height to try and estimate body fat. The resulting number is then used to categorize people as underweight, normal weight, overweight, obese, or morbidly obese. BMI is not perfect, however, and does not account for other factors that determine body composition like age, muscle mass, or sex. BMI calculations may, for example, overestimate body fat in athletes or in older people.

Lack of Sleep

For reasons that are not entirely clear, studies have shown that a lack of sleep is associated with a significant increase in the risk of type 2 diabetes.

It is thought the lack of sleep increases the production of the stress hormone cortisol. While cortisol can help keep you awake, having too much can dampen the production of insulin as well as the body's response to insulin.

As such, a chronic lack of sleep is considered by some to be a contributing risk factor for type 2 diabetes.

Older Age

The older we get, the greater the risk of insulin resistance and type 2 diabetes. This is thought to be due to aging-related changes to the pancreas that reduce its ability to produce and secrete insulin.

Aging liver cells, called hepatocytes, may also become less sensitive to insulin and be less able to regulate blood sugar levels.

Type 2 diabetes most often affects people over 45, but more children, teens, and young adults are developing it due to unhealthy dietary and lifestyle habits.

Genetics

Having family members with type 2 diabetes increases your risk of type 2 diabetes. Some studies have shown that having a mother or father with type 2 diabetes can increase your risk of the disease by up to threefold. With that said, it is no guarantee that you will get the disease.

Scientists have thus far identified more than 120 gene mutations associated with type two diabetes. Even so, the relationship between these mutations and the risk of type 2 diabetes is inconsistent.

In fact, there are very few single-gene mutations linked to type 2 diabetes. Most cases involve multiple gene mutations, and all almost invariably require lifestyle factors such as poor diet, lack of exercise, and obesity for type 2 diabetes to develop.

Because families tend to have similar dietary and lifestyle habits, the familial link to type 2 diabetes is thought to be influenced more by lifestyle than by genes.

Race and Ethnicity

Race and ethnicity can also factor into a person's risk of type 2 diabetes, with people of color disproportionately affected. While culture and lifestyle certainly play a part, some studies suggest the risk goes well beyond just weight or exercise.

According to a 2019 study from the Centers for Disease Control and Prevention (CDC), the rate of type 2 diabetes among racial/ethnic groups in the United States broke down as follows:

  • White people: 12.1%
  • Asian people: 19.1%
  • Black people: 20.4%
  • Latinx people: 22.1%

Metabolic Risk Factors

Hypertension (high blood pressure) and hyperlipidemia (high cholesterol) are hallmark risk factors for many diseases, including type 2 diabetes.Not only do these conditions contribute to the risk of heart disease, stroke, and chronic kidney disease (CKD), but they are also central components of metabolic syndrome.

Metabolic syndrome is a cluster of at least three of the following medical conditions:

  • Abdominal obesity: Defined as a waist circumference of more than 35 inches in females and 40 inches in males
  • Hypertension: Defined as a consistent systolic blood pressure reading of 130 or higher or a diastolic blood pressure reading of 80 or higher
  • Hyperglycemia: Defined as blood glucose levels greater than 125 milligrams per deciliter (mg/dL) while fasting
  • Hypertriglyceridemia: Defined as blood triglyceride levels greater than 200 mg/dL while fasting
  • Low levels of high-density lipoprotein (HDL): Described when "good" HDL cholesterol levels are below 40 mg/dL

Studies suggest that metabolic syndrome increases the risk of type 2 diabetes by five-fold compared to people without metabolic syndrome.

A Word From Verywell

Some risk factors for diabetes such as family history and genetic predisposition may be out of your control, but there's still a lot you can do to help manage your blood sugar and prevent the disease from progressing.

The key is to fully embrace a healthy lifestyle: Work with a nutritionist to make sure you're getting plenty of fiber, healthy fats, and the right nutrients, and find a personal trainer to help you get a fitness regimen that works with your abilities and schedule.

And don't forget about getting plenty of sleep and reducing your stress levels, too, as stress may also play a role in keeping blood sugar balanced.

Frequently Asked Questions

  • What is the most common trigger for type 2 diabetes?

    Type 2 diabetes typically starts with insulin resistance, a condition where the muscle, liver, and fat cells are unable to use insulin efficiently. As a result, the body needs more insulin to get glucose into the cells and over time, the pancreas is unable to keep up. Carrying excess weight and leading a sedentary lifestyle can lead to insulin resistance.

  • Can you get type 2 diabetes at any age?

    Yes, you can develop type 2 diabetes at any age. Even children can develop type 2 diabetes. However, it is more common in people over the age of 45. 

  • Why is age a risk factor for diabetes?

    As our bodies age, two things happen that increase the risk of diabetes: an increase in insulin resistance and a decrease in pancreatic islet cell function. The risk of type 2 diabetes increases at age 45. By age 65, roughly one-third of adults are diagnosed with type 2 diabetes. 

19 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Diabetes fast facts.

  2. Centers for Disease Control and Prevention. National Diabetes Statistics Report, 2020.

  3. Centers for Disease Control and Prevention. Adult obesity facts.

  4. Centers for Disease Control and Prevention. Childhood obesity facts.

  5. Santoleri D, Titchenell PM. Resolving the paradox of hepatic insulin resistance. Cell Mol Gastroenterol Hepatol. 2019;7(2):447-56. doi:10.1016/j.jcmgh.2018.10.016

  6. American Society for Metabolic and Bariatric Surgery. Type 2 diabetes and obesity: twin epidemics.

  7. Hackett RA, Dal Z, Steptoe A. The relationship between sleep problems and cortisol in people with type 2 diabetes. Psychoneuroendocrinology. 2020 Jul;117:104688. doi:10.1016/j.psyneuen.2020.104688

  8. De Tata V. Age-related impairment of pancreatic beta-cell function: pathophysiological and cellular mechanisms. Front Endocrinol (Lausanne). 2014;5:138. doi:10.3389/fendo.2014.00138

  9. Chia CW, Egan JM, Ferrucci L. Age-related changes in glucose metabolism, hyperglycemia, and cardiovascular risk. Circ Res. 2018 Sep 14;123(7):886–904. doi:10.1161/CIRCRESAHA.118.312806

  10. Zhang Y, Luk AOY, Chow E, et al. High risk of conversion to diabetes in first-degree relatives of individuals with young-onset type 2 diabetes: a 12-year follow-up analysis. Diabet Med. 2017 Dec;34(12):170-9. doi:10.1111/dme.13516

  11. Prasad RB, Groop L. Genetics of type 2 diabetes-pitfalls and possibilities. Genes (Basel). 2015;6(1):87-123. doi: 10.3390/genes6010087

  12. National Institute of Diabetes and Digestive and Kidney Diseases. Monogenic diabetes (neonatal diabetes mellitus & MODY).

  13. Ali O. Genetics of type 2 diabetes. World J Diabetes. 2013 Aug 15;4(4):114–23. doi:10.4239/wjd.v4.i4.114

  14. Cheng YJ, Kanaya AM, Araneta MRG, et al. Prevalence of diabetes by race and ethnicity in the United States, 2011-2016. JAMA. 2019 Dec 24;322(24):2389-98. doi:10.1001/jama.2019.19365

  15. National Heart, Lung, and Blood Institute. Metabolic syndrome.

  16. Moreira GC, Cipullo JP, Ciorlia LAS, Cesarino CB, Vilela-Martin F. Prevalence of metabolic syndrome: association with risk factors and cardiovascular complications in an urban population. PLoS One 2014;9(9):e105056. doi:10.1371/journal.pone.0105056

  17. National Institute of Diabetes and Digestive Kidney Diseases. Symptoms & causes of diabetes.

  18. National Institute of Diabetes and Digestive Kidney Diseases. Type 2 diabetes.

  19. Kirkman MS, Briscoe VJ, Clark N, et al. Diabetes in older adults. Diabetes Care. 2012;35(12):2650-64. doi:10.2337/dc12-1801

By Debra Manzella, RN
Debra Manzella, MS, RN, is a corporate clinical educator at Catholic Health System in New York with extensive experience in diabetes care.