Type 2 Diabetes Causes and Risk Factors

Type 2 diabetes mellitus (T2DM) occurs when the body cannot use insulin properly, causing sugar to build up in the blood. T2DM is the type of diabetes you can acquire due to risk factors like obesity and a lack of exercise. Research has also shown that genetics can predispose certain individuals to T2DM.

By identifying your risk factors for type 2 diabetes, you can take steps to avoid getting a disease that currently affects more than 34 million people in the United States.

What Causes Type 2 Diabetes?

Type 2 diabetes, formerly known as adult-onset diabetes, is the main type of diabetes characterized by insulin resistance and high blood sugar (hyperglycemia).

Glucose (sugar) is the body's main form of energy, without which our bodies cannot function efficiently. Insulin is the hormone produced by the pancreas that helps regulate blood glucose in two important ways:

• Glucose uptake: Insulin functions as a key to "open" cells so that they can utilize glucose for fuel.
• Glucose storage: When glucose levels are high, insulin will move it from the blood to the liver, muscles, and adipose (fatty) tissues for storage, restoring glucose to normal levels.

Insulin resistance occurs when cells become less responsive to insulin, depriving cells of fuel while causing blood glucose levels to rise.

In response to rising glucose levels, the pancreas will release even more insulin. But, over time, this can wear out the insulin-producing cells (known as pancreatic beta cells), causing insulin levels to plummet and blood sugar levels to rise to where they can damage tissues and organs.

It is at this point that a person is said to have type 2 diabetes.

Although the reason for this phenomenon remains a mystery, scientists have identified certain factors that can increase the risk of T2DM. Some of these risk factors are non-modifiable, meaning that you can't change them, while others are modifiable, meaning that you can.

Non-Modifiable Risk Factors

Age, genetics, and race are three risk factors for T2DM that you cannot change. With that said, by identifying your non-modifiable risks of T2DM, you can take steps to alter the risk factors that are modifiable.

Older Age

Anyone can get type 2 diabetes, but the risk significantly increases as you get older. Not only do aging pancreatic beta cells start to wear out, but so, too, do liver cells called hepatocytes that are tasked with releasing stored glucose.

With advancing age, hepatocytes may start to release excessive amounts of glucose into the bloodstream, making T2DM harder to control.

Because of these and other aging-related factors, type 2 diabetes mainly affects people over the age of 45. Studies have shown that roughly 9% of people of this age group are diagnosed with T2DM.

However, with unhealthy diets and lifestyle habits, more children, teens, and young adults in the U.S. are starting to develop T2DM, with nearly 2% developing the disease before the age of 30.

Genetics

Type 2 diabetes is not a genetic disorder, but certain gene mutations can predispose individuals to this chronic metabolic disease.

This has been evidenced by studies in twins and families, which have concluded that having a parent or sibling with T2DM independently increases your risk of the disease by anywhere from 25% to 69%.

The list of mutations associated with T2DM is extensive and includes genes known as SLC30A8, MC4R, PAM, UBE2NL, GCK, HNF1A, HNF4A, PDX1, GIGYF1, MAP3K15, and FAM234A, among others.

With that said, there are very few single-gene mutations linked to type 2 diabetes. Most cases involve multiple gene mutations, and almost all require lifestyle factors such as poor diet, a lack of exercise, and obesity for T2DM to develop.

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 play a part in these groups, studies suggest that race and ethnicity alone serve as independent risk factors.

According to a 2019 study from the Centers for Disease Control and Prevention (CDC), the rate of T2DM among racial/ethnic groups in the United States breaks down as follows:

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

The CDC research also suggests that American Indian, Alaskan Native, and some Pacific Islander people are at higher risk as well.

Modifiable Risk Factors

While certain people are predisposed to type 2 diabetes due to their genetics, race, or age, 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 determine if you get the disease or not.

Obesity

The number one risk factor for type 2 diabetes is having overweight or obesity.

A person is considered to be 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 meet the diagnostic criteria for obesity.

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

Obesity also independently triggers the onset of insulin resistance. Studies have shown that the increased accumulation of fat places cells under damaging stress, referred to as "lipotoxicity." This directly damages the fuel chambers of cells, called mitochondria, making them less responsive to insulin.

Risk factors for obesity include:

• A high-calorie diet
• Consuming excess saturated fats and trans fats
• Eating processed or sugary foods and beverages
• Lack of exercise
  

Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD)—better known today as metabolic dysfunction-associated steatotic liver disease (MASLD)—is characterized by the excess accumulation of fat in the liver. The accumulation of fat leads to an inflammatory state called steatohepatitis that affects how the liver functions.

The liver serves as a main repository for the stored form of glucose, known as glycogen. When blood sugar levels are low (referred to as hypoglycemia), the pancreas will release a hormone called glucagon that converts glycogen into glucose, which the liver then releases into your bloodstream.

With steatohepatitis, the liver has a harder time storing glucose, causing blood sugar levels to rise. Persistently high glucose levels, in turn, overtax pancreatic beta cells, causing them to wear out and progressively decrease insulin production.

Risk factors for NAFLD/MASLD include:

• Obesity: MASLD is found in no less than 75% of people who are overweight and in 90% of those with severe obesity.
• Metabolic syndrome: This is a condition characterized by hyperglycemia, hypertension (high blood pressure), hyperlipidemia (high cholesterol), and abdominal obesity (too much body fat around the waist).

How to Reduce Your Risk

Some risk factors like older age and a family history of T2DM can't be changed. However, as a disease triggered by unhealthy lifestyle choices, there are things you can do to significantly reduce your risk.

These include:

• Achieving a healthy weight: According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), you may be able to prevent or delay T2DM by losing 5% to 7% of your body weight if you have overweight or obesity. For instance, if you weigh 200 pounds, your goal would be to lose 10 to 14 pounds.
• Exercise regularly: It is important to engage in at least 30 minutes of moderate-intensity physical activity five days a week. Moderate-intensity exercise allows you to talk but not sing during the activity. Speak with your healthcare provider or a fitness professional to design a program that is safe and sustainable for your fitness level.
• Eat healthier: Start by eating smaller portions to reduce the amount of calories you eat each day. Limit your intake of fast foods, processed foods, fatty or fried foods, and sweets or sweetened beverages. Incorporate more fruits, vegetables, fresh fish, whole grains, and healthy unsaturated fats into your diet.

Small, gradual changes to your diet and exercise program are more sustainable than embarking on crash diets or high-intensity workouts (especially if you've never exercised before).

Summary

The hallmark of type 2 diabetes is insulin resistance, a condition in which your body is less responsive to insulin, leading to high blood sugar levels. Genetics, aging, and race play independent roles in the risk of T2DM, but lifestyle factors like obesity, an unhealthy diet, and lack of exercise play a larger role.

To delay or prevent T2DM, achieve and maintain a healthy body weight, engage in at least 150 minutes of moderate-intensity exercise each week, and eat a balanced diet lower in fat and sugar and higher in fruits, vegetables, fish, and whole grains.