Non-insulin-dependent diabetes - Causes of type 2 diabetes

Type 2 diabetes occurs when the pancreas doesn't produce enough insulin to maintain a normal blood glucose level, or the body is unable to use the insulin that is produced – known as insulin resistance.

The pancreas (a large gland behind the stomach) produces the hormone insulin, which moves glucose from your blood into your cells, where it's converted into energy.

In type 2 diabetes, there are several reasons why the pancreas doesn't produce enough insulin.

Risk factors for type 2 diabetes

Four of the main risk factors for developing type 2 diabetes are:

• age – being over the age of 40 (over 25 for South Asian people)  
• genetics – having a close relative with the condition (parent, brother or sister)
• weight – being overweight or obese
• ethnicity – being of South Asian, Chinese, African-Caribbean or black African origin (even if you were born in the UK)

See the introduction page for a full list of the risk factors for type 2 diabetes.

The four risk factors listed above are discussed in more detail below.

Age

Your risk of developing type 2 diabetes increases with age. This may be because people tend to gain weight and exercise less as they get older.

Maintaining a healthy weight by eating a healthy, balanced diet and exercising regularly are ways of preventing and managing diabetes.

White people over the age of 40 have an increased risk of developing type 2 diabetes. People of South Asian, Chinese, African-Caribbean and black African descent have an increased risk of developing type 2 diabetes at a much earlier age.

However, despite increasing age being a risk factor for type 2 diabetes, over recent years younger people from all ethnic groups have been developing the condition.

It's also becoming more common for children, in some cases as young as seven, to develop type 2 diabetes.

Genetics

Genetics is one of the main risk factors for type 2 diabetes.

Your risk of developing the condition is increased if you have a close relative – such as a parent, brother or sister – who has the condition. The closer the relative, the greater the risk.

A child who has a parent with type 2 diabetes has about a one in three chance of also developing it (see below).

Being overweight or obese

You're more likely to develop type 2 diabetes if you're overweight or obese (with a body mass index (BMI) of 30 or more).

In particular, fat around your tummy (abdomen) increases your risk. This is because it releases chemicals that can upset the body's cardiovascular and metabolic systems.

This increases your risk of developing a number of serious conditions, including coronary heart disease, stroke and some types of cancer.

Measuring your waist is a quick way of assessing your diabetes risk. This is a measure of abdominal obesity, which is a particularly high-risk form of obesity.

Women have a higher risk of developing type 2 diabetes if their waist measures 80cm (31.5 inches) or more. Asian men with a waist size of  89cm (35 inches) or over have a higher risk, as do white or black men with a waist size of 94cm (37 inches) or over.

Use the BMI calculator to find out if you're a healthy weight for your height.

Exercising regularly and reducing your body weight by about 5% could reduce your risk of getting diabetes by more than 50%.

Read more about losing weight.

Ethnicity

People of South Asian, Chinese, African-Caribbean and black African are more likely to develop type 2 diabetes.

Type 2 diabetes is up to six times more common in South Asian communities than in the general UK population, and it's three times more common among people of African and African-Caribbean origin.

People of South Asian and African-Caribbean origin also have an increased risk of developing complications of diabetes, such as heart disease, at a younger age than the rest of the population.

Other risks

Your risk of developing type 2 diabetes is also increased if your blood glucose level is higher than normal, but not yet high enough to be diagnosed with diabetes.

This is sometimes called "pre-diabetes" – doctors sometimes call it impaired fasting glycaemia (IFG) or impaired glucose tolerance (IGT).

Pre-diabetes can progress to type 2 diabetes if you don't take preventative steps, such as making lifestyle changes. These include eating healthily, losing weight (if you're overweight) and taking plenty of regular exercise.

Women who have had gestational diabetes during pregnancy also have a greater risk of developing diabetes in later life.