Ask the experts: Insulin resistance

With diabetes on the rise, HFG senior nutritionist Rose Carr looks at a related condition that’s becoming more prevalent.

What is insulin?

The hormone insulin plays a number of roles but its key purpose is to help control glucose levels in the blood.

Carbohydrates in food are broken down into glucose for use in the body and as blood glucose levels rise, insulin is secreted by the pancreas to help glucose be absorbed by our cells.

What does insulin resistance mean?

Insulin resistance means the body is becoming resistant to the effects of insulin, and we need to produce more insulin to have the same control over blood glucose levels. Insulin resistance is a precursor to type-2 diabetes and is often called pre-diabetes, or impaired glucose tolerance.

What health problems are related to insulin resistance?

Insulin resistance is a risk factor for heart disease and stroke, and is also strongly related to non-alcoholic fatty liver disease and for women, polycystic ovarian syndrome (PCOS).

Who’s at risk for developing insulin resistance?

Both genetic and lifestyle factors affect our chances of developing insulin resistance. And as we get older, our risk inevitably increases, even from our mid-30s, but being overweight, especially around the middle (or waist), is one of the most significant risk factors we can change. If we don’t exercise regularly or do enough physical activity throughout the day, we’re also putting ourselves at risk.

High blood pressure, high triglycerides and low levels of high-density lipoprotein (HDL), our good cholesterol, each increase our risk for insulin resistance; likewise if we already have heart disease or have suffered a heart attack. People with Chinese, Indian or Pacific Island heritage have a greater risk than others, but any family history of type 2 diabetes also increases our risk. For women, having gestational diabetes, a baby who weighed more than 4kg, or PCOS are also risk factors.

What should I do if I’m told I have insulin resistance?

Put simply, you need to improve your diet and up the exercise. This two-pronged approach can help with weight loss – which helps to increase our insulin sensitivity – and reduce the need for insulin by reducing the amount of high glycaemic-index carbohydrates we eat. And if you smoke, stop now; you’re about 50 per cent more likely to develop type 2 diabetes than a non-smoker.

While there’s no perfect diet that’s right for everyone, we do know the healthiest diets are based on having lots of plant foods and fewer processed foods. A Mediterranean-style diet, including lots of vegetables, oily fish, whole grains, nuts, olive oil and small amounts of red meat and dairy has been shown to lower the risk for insulin resistance in people previously eating a more traditional Western diet.

Vegetarian diets have also been shown to be protective for type 2 diabetes, with vegan diets being the most protective. If you need a starting point for dietary change, try increasing your vegetable intake and cutting out some of those high-energy extras.

Exercise simply means using our muscles; this helps improve their ability to use insulin and absorb glucose. We don’t even need to break into a sweat to do this. Even moderate exercise, such as walking for 30 minutes on most days has been shown to be effective in improving insulin sensitivity. Conversely, research has found that the longer we spend sitting on the couch watching the box the more likely we are to develop diabetes; probably because we’re likely to be heavier.

What is hyperglycemia?

Our bodies normally manage blood glucose levels well but if we develop insulin resistance, it becomes more difficult to maintain this balance. This can result in hyperglycemia, where our blood glucose level is higher than normal.

What the numbers mean

The glycalated haemoglobin (HbA1c) test is used to screen for type 2 diabetes.

• HbA1c 50 mmol/mol or more indicates diabetes (but does not confirm a diagnosis by itself)
• HbA1c 41-49 mmol/mol indicates insulin resistance or pre-diabetes
• HbA1c 40 mmol/mol or less is normal

In New Zealand:

• The overall prevalence of diabetes is 7.0%
• This is higher in men (8.3%) than women (5.8%).
• It’s also higher in people who are obese (14.2%) , compared to people in the healthy weight range (2.5%)
• A further 25.5% of adults have insulin resistance (pre-diabetes).
• Prevalence of undiagnosed diabetes is highest among Pacific people at 6.4%.

Source: Journal of the New Zealand Medical Association, March 2013