Diabetes is a ‘chronic’ health condition that is associated with insulin production and the body’s ability to use it.

In this article, we will be exploring the causes of type 2 diabetes. We are going to address answers to ‘what is the root cause of type 2 diabetes’ and find out the role of genetics in diabetes.

Before that, let’s explore some background about diabetes.

Written by Shani, an Australia-base Registered Healthcare Practitioner with a Masters qualification from the University of Newcastle (Australia) and with decades of hands-on experience working for hospitals and in aged-care.

What is Insulin?

Insulin, as you may already know, is a hormone produced by cells in the pancreas known as the ‘beta cells of the pancreatic islets’.

Insulin enables your body to use the glucose from the carbohydrates you ingest to produce energy or to store the excess glucose in the liver for future use. Thus, insulin is a regulatory hormone that helps to keep the blood sugar level within the normal range.

Without the presence of insulin, the body cells cannot make use of the glucose to generate energy. This condition with low insulin leads to an accumulation of glucose in the blood and ultimately, an increased blood sugar level (hyperglycemia).

Diabetes is a medical condition that is majorly characterized by increased blood sugar levels (hyperglycemia as noted above).

It is of two types – Type 1 and Type 2, but our primary focus in this article is on Type 2 Diabetes and its causes.

Type 2 Diabetes Mellitus: Insulin Resistance versus Insulin Insufficiency

Different things can cause diabetes. The underlying cause of diabetes would also determine whether it is Type 1 or Type 2.

While type 1 diabetes is caused by a lack of insulin production, which ultimately causes insulin insufficiency, type two is caused mainly by insulin resistance.

What causes insulin insufficiency in type 1 diabetes?

In the case of type 1 diabetes, the beta cells of the pancreatic islets, which are responsible for the production of insulin, are damaged, thus interfering with the creation of insulin. Since insulin is needed to transport blood sugar into the cells, this condition causes a shortage of insulin, and the result is that high amounts of sugar accumulate in your blood.

What causes insulin resistance in type 2 diabetes?

In type 2 diabetes, however, there is no damage to the pancreatic cells that produce insulin. In fact, insulin is produced in normal amounts; however, the body is just resistant to it, i.e. the body is unable to make use of it.

When this happens, the body goes through a positive feedback mechanism trying to salvage the situation by producing more insulin. The cells still won’t be able to utilize them efficiently.

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When the amount of insulin in the blood increases, the pancreas eventually slows down the hormone production.

In type two diabetes, just like in type 1, the amount of glucose in the blood also accumulates but, in this case, as a result of insulin resistance.

Tip: Diabetes Mellitus and Diabetes Insipidus are too different, although they can cause similar diabetes symptoms.

What is Pre-diabetes?

In Type 2 Diabetes, at that initial point, when the blood glucose level increases, it is known as prediabetes. Prediabetes indicates a slightly higher glucose level but not high enough to diagnose the condition as ‘diabetes’.

There may not have distinct symptoms of pre-diabetes at this point, and the person may not know unless tested for diabetes.

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Untreated prediabetes could escalate and lead to diabetes as in the case of type 2 diabetes which occurs as insulin production reduces and its resistance increases.

What are the causes of type 2 diabetes?

Below, we would be discussing the role some factors play in the development of type 2 diabetes.

Role of genetic factor in causing type 2 diabetes

Among the causes of diabetes, lifestyle and genetics have been indicated as the most important ones. A combination of the two is much too likely to cause insulin resistance.

Tip: Add these exercises for your routine to delay or escape from diabetes.

An article published in the World Journal of Diabetes confirms that type 2 diabetes is caused by an interaction between environmental factors and hereditary component.

Also, with the advancement in genetics and the advent of wider genome association studies, more multiple genes are being identified, including those that were not previously linked to diabetes type 2.

Tip: Here are the most popular diabetes myths.

How does genetics play a role in the development of type 2 diabetes?

Different theories show that diabetes type 2 is linked to genetics.

A family history of diabetes

Perhaps, you have been diagnosed with type 2 diabetes. If you have, then check this out; there is every possibility that you are not the first person that has been diagnosed with this condition in your family.

Science has proved that you are at a higher risk of developing diabetes when one of your family members of your blood-line has it.

Gene mutations

Scientists and researchers have linked several gene mutations to increased risk of developing diabetes. Of course, when the gene mutations interact with each other and with environmental factors, they would further increase the chances of developing type two diabetes.

Diabetes type 2 is mostly in ‘polygenic’ forms. This means defects or changes in multiple genes usually cause them.

However, there are also ‘monogenic’ forms of diabetes, which are caused by changes or mutations in a single gene. They can either develop on their own or is inherited from family.

Even though not everyone with a gene mutation develops diabetes, many people diagnosed with diabetes show mutation of one or more genes.

Lifestyle of parents

It is usually not easy to detach environmental factors from genetic factor. Family members can influence even the environmental risks.

For instance, when parents have developed a good eating habit, they are much likely to pass this down to their children. While genetics believed to play a big part in determining the weight, healthy eating habits play a role too.

Genes associated with type 2 risk

When genes that are associated with controlling your blood sugar levels mutates, you have higher chances of having type 2 diabetes.

Some of the genes involved here include the below.

  • GLUT2 – It helps transport glucose into the pancreas.
  • ABCC8 – It helps in insulin regulation.
  • TCF7L2 – It influences both the production of glucose and the secretion of insulin.
  • GCGR – It is a gene for glucagon hormone, which helps in the regulation of glucose.
  • CAPN10 – This gene has been indicated to be associated with the risk of type 2 diabetes, mostly in the Mexican-Americans.

Role of low birth weight in causing type 2 diabetes

Different studies have confirmed that low birth weight is linked with higher rates of insulin resistance, type 2 diabetes and obesity even though the exact mechanism of this link is still vague.

low birth weight

In a research carried out to assess the link between birth weight and obesity or the markers of glucose homeostasis in adults, it showed a higher prevalence of diabetes in middle-aged adults that were born with low weight when compared to the ones born with the normal birth weight.

Leptin and type 2 diabetes

Those born with low birth weight also showed higher leptin levels and leptin to fat mass ratio, and this was suggested to be associated with nutritional factors during childhood or possibly as a result of leptin resistance.

Leptin is a hormone which your adipose tissue produces and does increase with type 2 diabetes. It is also highly linked with obesity.

A suggestion has been put forward that children with low birth weight have an increased leptin level during ‘catch-up’ growth, and this could possibly imply resistance to leptin.

Low-fat mass and type 2 diabetes

In another study, a low deposition of fat, which leads to low birth weight at birth, would lead to the acquisition of fat during the later childhood years. As the child grows and advances to adulthood, this would predispose to diabetes type 2.

Your father and type 2 diabetes

It is also not known whether the relationship between birth weight and the development of type 2 diabetes is associated with environmental and genetic factors.

However, another study carried out using 1608 children (with known birth weight) born between 1941 and 1993 in a community in Arizona indicated that the children born of diabetic fathers were on the average about 78g lighter in weight than the children of non-diabetic fathers.

This means that paternal inheritance could play a role in this as the fathers who had kids with lower birth weight were said to have a higher risk of developing diabetes later in life.

Motherhood nutrition and type 2 diabetes

Apparently, the low birth weight reflects intrauterine (inside mother’s womb) nutrient conditions which have been linked with metabolic disorders after birth, obesity and resistance to insulin.

Role of poor childhood nutrition in causing type 2 diabetes

Healthy nutrition and diet during childhood stage and adolescence stage are essential not only for enhancing growth and development but also for preventing different health conditions.

As you know, type 2 diabetes mellitus is a chronic disease condition with multifactorial etiology (interplay of epigenetic, genetic and environmental factors).

Recently, shreds of evidence gathered from experiments involving both humans and animals have linked early life factors such as nutrition with increased diabetes risk in adulthood.

As you must have known, the fetal and neonatal period is a very crucial point of the development of every organ. A good number of factors during pregnancy can very well predispose one’s offspring to diabetes in the future. Inclusive in the factors are malnutrition and lifestyle.

Tip: Must know early warning signs of diabetes in adults and children were covered before.

Poor maternal malnutrition

Poor nutrition is seen as an unfavorable environment, which could increase the risk of developing type 2 diabetes.

Altered gene expression in the fetus during this period as a result of maternal malnutrition has been suggested to be the cause of cell dysfunction as well as greater susceptibility to diseases.

There is also evidence that early weaning could result in under-nutrition, which is likely to cause metabolic disorders in the future. Experiments done with some rats showed higher insulin resistance index, hyperglycemia and hyperleptinemia in the rats that were weaned early.

Role of pancreatic diseases, insulin secretion, insulin function and impaired glucose tolerance in causing Type 2 Diabetes

There is a direct connection between the pancreas and diabetes.

The pancreas plays an important role in the digestion of food and forms an important part of the digestive system. Asides producing enzymes that digest foods, it also produces and secretes other important hormones like the Insulin, which acts to regulate blood sugar level.

When the pancreas is impaired, it could affect the production of insulin, and when insulin is not sufficient, it would ultimately lead to the build-up of glucose in the blood – a case of hyperglycemia.

Hyperglycemia is the chief sign of diabetes.

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Tip: depending on your diagnosis, your food list may differ. For example, diabetes diet, hypoglycemia diet, diabetic gastroparesis diet.

Pancreatic diseases that can cause diabetes

Below, are certain pancreatic diseases or conditions that can cause diabetes.


This is an inflammation of the pancreas.

Pancreatitis can be acute (comes suddenly and lasts for only a few days to weeks) or chronic (when it occurs over the course of some years).

Chronic pancreatitis can cause damage to the Beta cells of the islets of Langerhans, which is responsible for the production of insulin, thus, leading to diabetes.

Some studies have shown that the two share similar risks. Also, people with pancreatitis have a higher risk of developing diabetes and vice versa.

Pancreatic cancer

This is the cancer of the pancreas. There is a link between pancreatic cancer and diabetes through this link seems complex.

The Pancreatic Cancer Action Network reports that individuals who have been diagnosed with diabetes for five or more years are twice more likely to develop pancreatic cancer. Also, the manifestation of diabetes later in life could be linked back to this cancer. Both are interlinked.

Cystic fibrosis

Cystic fibrosis is a condition in which sticky mucus forms in the pancreas, which ultimately results in scarring of the pancreatic tissue. This can cause the development of insulin-requiring diabetes as the sticky mucus could inhibit the production of insulin. This leads to the formation of Cystic Fibrosis-related Diabetes (or CFRD). CFRD is hardly detected until a test for diabetes is performed.

Asides the above-listed disorders, other pancreatic disorders can also easily predispose one to diabetes such as impaired glucose tolerance.

What is impaired glucose tolerance?

Impaired glucose tolerance simply means when the blood glucose level is high, above the normal glucose level (within the range of 4-8 mmol/L) but not high enough for it to be termed ‘diabetes’. For this reason, it is also called ‘prediabetes‘.

That is to say, if you don’t manage the condition at that point, it could eventually result in diabetes. This condition is also known as impaired fasting glucose and doesn’t only predispose to diabetes but also other diabetes complications such as cardiovascular diseases.

The chances of progressing from prediabetes to diabetes

A research report indicates that 1-3 out of every four persons with impaired glucose tolerance will become diagnosed with diabetes within a period of 10 years.

There is no exact estimate for the prevalence of this condition because a good number of people with it don’t even know they have it as it usually doesn’t present with symptoms.

However, an article on diabetes UK proposes that about 7 million people in the UK itself have this condition.

Other insulin-related factors do play a role in the development of type 2 diabetes later in life.

Any factor or disorder that affects insulin production, its secretion or its actions would definitely predispose you to diabetes.

In the case, of insulin resistance, the liver, muscles and fat cells would be unable to make efficient use of the insulin even when the pancreas produces it.

Tip: Watch for these diabetes symptoms specific to women and men.

Role of obesity in causing type 2 diabetes

What is obesity?

In simple words, obesity is a condition in which one has too much or excessive fat (also called adipose tissue). Alternatively, it is when one has a Body Mass Index (BMI) of 30 and above.

Different factors can cause obesity in people, and such factors include; sedentary lifestyle, hereditary and family history, eating unhealthy foods as well as certain medications and health conditions.

Obesity and type 2 diabetes

Obesity is also said to be one of the most significant predictors of diabetes type two. But, how and why?

In a bid to answer this question, some researchers at the Harvard University
came up with a novel pathway that triggers a chain of reactions, which is very much likely to cause the development of insulin resistance, which is the major cause of type two diabetes mellitus.

Endoplasmic reticulum stress

According to this research, obesity imposes stress on a collection of cell membranes called the endoplasmic reticulum (ER). When imposed with stress, the endoplasmic reticulum, in turn, acts to inhibit the signalling of insulin receptors (remember, without signalling of the receptors, the insulin hormone cannot bind to the cell to act on it). Thus, the individual develops resistance to insulin.

The endoplasmic reticulum stress is also said to induce inflammation. Some other studies agree that asides from increasing the levels of fatty acid, obesity also triggers inflammation, which in turn leads to insulin resistance. In this case, glucose ultimately builds up in the blood as the cells are unable to utilize them, thus leading to diabetes.

With this, you should know one of the effective management schemes of diabetes is to lose weight or better still, control your weight.

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Tip: Here are the home remedies of type 2 diabetes you must know about.

Other causes of type two diabetes

Asides the above factors or disease conditions discussed, there are other conditions that can cause diabetes such as;

Hormonal diseases

Certain hormonal disease conditions can trigger the body to produce some hormones, which in turn acts to cause insulin resistance and eventually, diabetes. Examples of the hormonal disease conditions are Cushing’s syndrome, hyperthyroidism
and acromegaly.

Total removal of the pancreas

Sometimes the pancreas gets so damaged that it has to be surgically removed. In this case, the beta cells of islets would be lost predisposing one to diabetes.


Hemochromatosis is a condition that causes one’s body to store too much amount of iron. When left untreated, it can lead to a build-up of iron, which in turn poses serious damage to the pancreas as well as other organs.

Certain medications

You have to be wary of the medications you take. Be sure your physician prescribes them and take them within the stipulated time and with the right dosage.

That’s because, sometimes, certain medications could disrupt insulin production by causing harm to the beta cells that secrete insulin. Examples of such medicines include; psychiatric drugs, anti-seizure medications, pentamidine, glucocorticoids and even niacin (a type of vitamin B3).

What are the risk factors for type 2 diabetes?

Your chances of developing type 2 diabetes depend on the combination of different risk factors such as lifestyle and genes. You may not be able to change ‘unmodifiable’ factors like your gene or ethnic background, but you can change those pertaining to your lifestyle pattern.

The following risk factors are likely to increase your chances of developing type 2 diabetes;

§ Obesity or being overweight – this is one of the major risk factors.

§ Age – Age 45 and above have higher chances of developing diabetes

§ Genes or a family history of diabetes

§ People of the African American, American Indian, Alaska, Asian American, Native Hawaiian or Hispanic/Latino origin

§ Hypertension (and, here are the causes of hypertension)

§ Inactivity or living a sedentary lifestyle

§ A history of cardiovascular disease

§ A high level of triglycerides or low level of HDL cholesterol

§ Depression

§ Women with cases of polycystic ovary syndrome

§ Acanthosis nigricans (manifests as thickened, darkened or velvety skin usually around the neck and armpit)

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In summary

Different things can predispose one to type 2 diabetes mellitus. Factors such as gene, lifestyle, nutrition, disease conditions will always play a role. Also, a good number of risk factors are likely to lead to the development of this condition. However, the good news is that it can be managed by certain adjustments in lifestyle as well as with the use of medications.

Tip: Here are the best glucose monitoring devices. Think again before you consider Dario Glucose Meter and A1c Testing.