SOME QUESTIONS AND ANSWERS

Why is obesity linked with diabetes?

Obesity is linked with type 2 diabetes, although not with type 1, because it results in insulin resistance.

About 80 per cent of those with type 2 diabetes are overweight, and the risk of developing the disease increases progressively as body mass index (BMI - weight in kg divided by height in m2), waist-to-hip ratio, waist circumference, or, more specifically, the amount of deep abdominal body fat increase. Excess deep abdominal fat may lead to insulin resistance, type 2 diabetes, abnormal blood fat levels and the onset of cardiovascular disease.

Although body mass index has been the most commonly cited risk factor for developing diabetes, recent data have shown that waist circumference may be a more accurate indicator than BMI. Guidelines now identify a waist circumference of more than 88cm in women or 102cm in men as indicating those with the highest risk of developing type 2 diabetes and cardiovascular disease.

Changes in the number, type and location of fat cells in body fat, muscle and the liver are central to the development of insulin resistance in obese people. Large, insulin-resistant fat cells in deep abdominal fat release increased amounts of non-esterified fatty acids (NEFA) into the portal vein, from where they enter the liver and then the general circulation. This increases liver output of glucose (hyperglycaemia) and triglycerides. Raised levels of NEFA, glucose and triglycerides cause insulin resistance (reducing glucose uptake by muscles) and damage the beta-cells of the pancreas, reducing insulin secretion and further worsening hyperglycaemia.

These damaging changes can be prevented, or at least moderated, through diet and exercise, particularly at the stage of pre-diabetes, reducing the risk of developing diabetes, and this has been demonstrated by several large clinical studies. Exercise is particularly effective in reducing deep body fat cell mass. Lifestyle change, including dietary changes as well as exercise, is the bedrock of all attempts to prevent and treat diabetes and to slow development of longer-term complications.

Is it necessary to eat special diabetic foods?

No. The basis of a healthy diet in diabetes is the same as for anyone else: a balanced diet, containing foods from all the major food groups, that is low in fat, salt and simple sugars.

Diabetic versions of sugar-containing foods offer no special benefits. They may still raise blood glucose levels, are usually more expensive, and can also have a laxative effect.

It is not necessary or desirable to cut out carbohydrates from the diet. Starchy carbohydrates, such as cereals, pasta and wholegrain bread, are an important component of a healthy, balanced diet, as are all fruits and vegetables. Cutting down on fatty and sugary foods will help in losing weight in a controlled way over time (0.5-1 kg a week) and will benefit blood glucose control.