Type 2 diabetes occurs when the pancreas does not produce enough insulin to maintain a normal blood glucose level, or your body is unable to use the insulin that is produced (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 is converted into energy.
In type 2 diabetes, there are several reasons why the pancreas doesn't produce enough insulin.
These are discussed below.
Risk factors for type 2 diabetes
You are more likely to develop type 2 diabetes if you:
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 through a healthy, balanced diet and exercising regularly are ways of preventing and managing diabetes.
Type 2 diabetes often develops in white people over the age of 40. People of South Asian, African, African-Caribbean and Middle Eastern descent have an increased risk of developing type 2 diabetes at a much earlier age.
However, in recent years, an increasing number of younger people from all ethnic groups are developing the condition.
It is also becoming more common for children, in some cases as young as seven, to develop type 2 diabetes.
Genetics is one of the main risk factors for type 2 diabetes. Your risk 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).
People of South Asian, African, African-Caribbean and Middle Eastern descent are more likely to develop type 2 diabetes.
The condition is up to six times more common in South Asian communities than in the general UK population, and it is three times more common among people of African and African-Caribbean origin.
Being overweight or obese
If you are overweight or obese (you have a body mass index of 30 or greater), you are at greater risk of developing type 2 diabetes.
In particular, fat around your abdomen (tummy) puts you at increased risk. This is because it releases chemicals that can upset the body's cardiovascular and metabolic systems. This then increases your risk of a developing various conditions, including heart disease, stroke and some types of cancer.
A quick way of assessing your diabetes risk is to measure your waist. 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 31.5 inches (80cm) or more. Asian men with a waist size of 35 inches (90cm) or over have a higher risk, as do white or black men with a waist size of 37 inches (94cm) or over.
Reducing your body weight by about 5% and exercising regularly could reduce your risk of getting diabetes by more than 50%.
Read more about losing weight.
Your risk of developing type 2 diabetes is also increased if you have impaired fasting glycaemia (IFG) or impaired glucose tolerance (IGT).
These conditions are sometimes referred to as "pre-diabetes" and mean that your blood glucose level is higher than normal but not high enough to cause diabetes. IFG and IGT can both progress to type 2 diabetes if you do not take preventative steps.
Women who have gestational diabetes during pregnancy also have a greater risk of developing diabetes in later life.
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