I am a 35-year-old man with a family history of diabetes. My BMI is 25.

I understand that pre-diabetes is defined as a fasting blood glucose level of either 100-125mg/dl or 108-125mg/dl.

I have seen some doctors using the fasting glucose range, together with a HbA1c reading of more than 5.7 per cent as a way to predict risk.

What are the considerations for using the two ranges and what should I do if my fasting glucose is 105mg/dL and my HbA1c is 6 per cent?

My doctor told me to halve my carbohydrate intake, double my intake of vegetables, drink plain water and exercise every three days. Is this really effective?

Type 2 diabetes often runs in families. If your family members have this condition, your risk rises but it is never too late to take action to lower your risk.

The best way to start is to adopt a healthy lifestyle.

The American Diabetic Association uses a fasting blood sugar of 100mg/dl-125mg/dl to define pre-diabetes. The World Health Organisation (WHO) defines it as 110mg/dl-125mg/dl.

Based on various population studies, we often define blood sugar levels by these categories – normal, pre-diabetes and diabetes – but there are grey areas at each cut-off point.

For example, if we use 32 deg C to define a hot day when heat injuries could occur, it does not mean that at 31 deg C, it is not hot and we will not get heat injuries.

In the case of diabetes, it is clear that the higher the blood sugar levels, the higher the risk of diabetes and its associated complications, such as heart disease and stroke.

The American Diabetic Association recommends using the HbA1c or glycated haemoglobin level of 5.7 per cent to 6.4 per cent to define pre-diabetes.

The HbA1c test shows a person’s blood sugar control over the past 120 days. It measures how much glucose has been in the blood.

Normally, some glucose will stick to haemoglobin, the blood pigment that makes your blood red and carries oxygen to your organs. This blood sugar-haemoglobin complex is called HbA1c.

We do not routinely use HbA1c to define or screen for pre-diabetes or diabetes because the values recommended by the American Diabetic Association have not been vigorously validated in our population.

Moreover, we have a higher prevalence of a genetic blood disorder called thalassemia, which can affect the way haemaglobin binds with the blood sugar, thus affecting the accuracy of HbA1c.

According to WHO guidelines, you are not considered pre-diabetic with a fasting blood sugar of 105mg/dl but with a body mass index (BMI) of 25.

If you are overweight and have a family history of diabetes, you are at a higher risk of contracting pre-diabetes and diabetes.

To reduce your risk, you need to adopt a healthy lifestyle.

Eat right as this can help control chronic diseases like high blood pressure and high cholesterol.

Based on the Health Promotion Board recommendations, about 50 per cent of your meal should come from fruit and vegetables, 25 per cent from wholegrains such as brown rice, wholemeal bread or oats, and 25 per cent from lean meat, eggs or low-fat dairy products.

Next, exercise regularly. Ideally, do 150 minutes of moderate-intensity aerobic exercise a week, to reduce the risk of chronic diseases.

Moderate intensity means that you will only be able to talk, but not sing, while exercising. You could consider activities like brisk walking, cycling, dancing and swimming.

If you have not been exercising much, start slow. Focus on gradually increasing the frequency and then the intensity.

You should also drink in moderation and not smoke.

Following a healthy diet and staying active will help you maintain a healthy weight. Asians should aim for aBMIof 18.5 to 23.