While it is already known that an unhealthy lifestyle increases the risk of type 2 diabetes, a new study has found that this risk increases even more if a person had a low birth weight.

According to US researchers, diabetes is a global epidemic, with 387 million people worldwide now estimated to be affected. Last year, almost five million deaths were due to the condition.

Both early life development and an unhealthy lifestyle are viewed as risk factors, however few studies have investigated their joint effect on risk. The researchers decided to look into this further by assessing the joint impact of a low birth weight and lifestyle risk factors.

They focused on five lifestyle factors - diet, physical activity, body mass index (BMI), smoking and alcohol consumption.

The study involved tracking the health of almost 150,000 healthy men and women every two years over a period of 20-30 years. During this time, almost 12,000 new cases of type 2 diabetes were detected.

The researchers found consistent links between having an unhealthy lifestyle and the risk of type 2 diabetes. They also found consistent links between having a low birth weight and risk of the disease.

However, the study also noted a ‘significant interaction' between having a low birth weight and having an unhealthy lifestyle.

"The attributable proportions of joint effect were 22% to lower birth weight alone, 59% to unhealthy lifestyle alone, and 17% to their interaction. This means that 17% of diabetes cases would occur if both lower birth weight and unhealthier lifestyle were present, but not if only one was present - implying that some type 2 diabetes cases depend on both prenatal and later life factors," the study noted.

These findings also suggest that the consequences of having an unhealthy lifestyle may be more far reaching in people with a low birth weight.

"In summary, we found that both low birth weight and unhealthy lifestyle were associated with a significantly higher risk of type 2 diabetes, and the effects of low birth weight combined with the unhealthy lifestyle score were more than the addition of the risks associated with each individual factor," explained the researchers from Harvard.

They added that the findings indicate that most cases of type 2 diabetes ‘could be prevented by the adoption of a healthier lifestyle, but simultaneous improvement of both prenatal and postnatal factors could further prevent additional cases'.

Details of these findings are published in the British Medical Journal.