Type 2 Diabetes Causes

The causes of type 2 diabetes

Last reviewed: 23 Mar 2019

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Contents of this article

Type 2 diabetes is a condition that causes the level of glucose (sugar) in your blood to be higher than normal. Genetics and lifestyle choices can both affect how likely you are to get type 2 diabetes. Specifically, if you are overweight, you don’t get enough exercise, or someone in your family has diabetes already, you’re more likely to get it yourself.

What causes type 2 diabetes?

The condition ‘type 2 diabetes’ is caused by the glucose (sugar) levels in your blood being consistently too high. This usually happens because:

  • your body can’t produce enough of a hormone called ‘insulin’, which is used to control blood sugar
  • the insulin your body is producing isn’t able to do its job

These insulin problems can be caused by a few genetic or lifestyle-related factors.

Insulin is a chemical (hormone), made by the pancreas, which usually lets glucose enter our cells and provide energy to the body. In type 2 diabetes, the level of glucose in the blood increases because it’s entering the blood from the digestive system, but the glucose can’t enter the cells. This means that glucose starts to build up in your blood and causes the symptoms of diabetes. As mentioned above, this can happen because there isn’t enough insulin in the first place, or the cells can’t use it properly (insulin resistance).

Insulin resistance is when cells don’t respond well to the insulin that’s made, and they can’t take up the glucose from the blood. As the glucose level in the blood continues to increase, the pancreas makes more insulin to try and solve the problem. Eventually, the pancreas becomes so tired that it makes less and less insulin with time, which makes it even harder for glucose to leave the blood. Both your genetics and lifestyle can have an impact on the development of insulin resistance.

Genetic causes of type 2 diabetes

Type 2 diabetes can be hereditary, which means that if other members of your family have had type 2 diabetes, you have a higher chance of developing it too. It’s not clear exactly how it gets passed on, but we do know that the risk of developing type 2 diabetes increases with the number of family members who have it already.

When some genes are mutated, this appears to be linked to an increased risk of type 2 diabetes. Some of these genes linked with a higher risk of type 2 diabetes include:

  • ABCC8: this helps manage insulin levels
  • GLUT2: this helps move glucose into the pancreas
  • GCGR: this is involved in managing glucose levels

There are tests available for some of the gene mutations linked with type 2 diabetes. But, the increased risk for each individual mutation is small, and other factors are far more useful in figuring out if you’re at risk of type 2 diabetes, including:

Lifestyle causes of type 2 diabetes

Genetics can affect your risk of type 2 diabetes, but lifestyle choices are a factor too, including:

  • enough exercise: getting enough physical activity can help you avoid type 2 diabetes if you’re already at risk
  • unbalanced diet: if your diet consists of a lot of high-fat foods and doesn’t have much fibre, this can increase your chance of getting type 2 diabetes
  • being overweight: if you’re overweight, then it’s more likely that you’ll become insulin resistant and get diabetes. Being overweight can also make diabetes symptoms worse

What risk factors make it more likely you’ll get diabetes?

Specific genes aren’t the only factors that can increase your risk of type 2 diabetes. Some of the other risk factors for type 2 diabetes are:

  • Race/ethnicity: being of South Asian or African-Caribbean descent and living in a developed country means you’re more likely to get type 2 diabetes
  • Lifestyle factors: not enough exercise, an unbalanced diet, or being overweight
  • Age: the risk of developing type 2 increases with age. At 45, your risk starts to rise, and after 65, your risk increases at even more
  • Gestational diabetes: some women develop diabetes during pregnancy, which increases the risk of developing type 2 diabetes later in life
  • Polycystic ovary syndrome: this is an ovarian condition in women, which raises the risk for type 2 diabetes, because it’s related to insulin resistance

How to avoid the causes of diabetes

Living a healthier lifestyle, including exercise and a balanced diet, can help prevent type 2 diabetes. Some of the reasons it helps are:

  • If you're insulin resistant, a healthy lifestyle can help increase your body's response to insulin
  • Muscles can use up glucose without needing insulin. This means even if you’re insulin resistant or if you don’t have enough insulin, muscle cells can help you regulate your blood sugar level

Living a healthier lifestyle: your doctor can give you detailed info about a healthy lifestyle and what you can do to help keep type 2 diabetes under control. Some things to cover are:

  • Keeping active
  • Losing weight, if you’re overweight
  • Quitting smoking, if you smoke
  • Drinking less alcohol

Eating a more balanced diet: eating healthily, and losing weight if you’re overweight, will help you to manage your diabetes or risk of diabetes better. You might want to consider seeing an expert (dietician) who can give you advice about your diet, and help you build it around your lifestyle, culture, beliefs, and preferences. A dietician will also inform you about the best times to eat, how much carbohydrate you should eat per meal and how much alcohol you can drink. Some of the advice you get might include:

  • Getting your carbohydrates from fruit, vegetables, pulses and whole grains
  • Eating oily fish
  • Eating low-fat dairy products
  • Limiting the food you eat with ‘bad’ fats

Managing your weight: if you’re overweight, you’ll be encouraged to lose weight, and to agree on a target amount of weight to lose. The weight loss target usually starts at 5-10% of your weight, and will change over time. Any weight loss will help, but the nearer you get to a suitable body weight, the better your long‑term health will be.

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Dr Kathryn Basford is a qualified GP who works as a GP in London, as well as with Zava. She graduated from the University of Manchester and completed her GP training through Whipps Cross Hospital in London.

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Last reviewed: 23 Mar 2019

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