South Asians (from Bangladesh, Pakistan, and India) need more exercise than than White Europeans to reach the same levels of fitness and decrease their risk of diabetes, according to new research by a team at the University of Glasgow.

The finding, published in the journal Diabetologia, revealed that exercise guidelines may need to be updated to account for ethnicity.

Diabetes occurs when there is an excess amount of sugar in the blood because the body is not making enough of the hormone insulin — which keeps blood sugar levels normal by helping cells use it for energy — or when the body does not respond properly to the presence of insulin (insulin resistance).

In the UK, it has been known that South Asians living there have a 3 to 5 fold higher incidence of type 2 diabetes, and develop the disease an estimated decade before and at a lower body mass index (BMI), than white Europeans.

South Asians who are non-diabetic even have raised blood sugar levels – higher than Europeans. Experts are not sure why, but believe it is due to a greater resistance of body cells to the effects of insulin.

Key factors that have an impact on insulin resistance, blood sugar levels and diabetes risk include:

  • low physical activity levels
  • carrying too much fat
  • low level of fitness

In the current study, researchers set out to measure the extent to which elevated insulin resistance and blood sugar levels in South Asian men, compared with white European men living in the UK, was caused by lower fitness and physical activity levels.

The investigators observed 100 South Asian and 100 European men aged 40 to 70 years living in Scotland without diabetes. They measured their insulin resistance, blood sugar levels, and other risk factors.

Participants took part in a treadmill exercise to determine how much oxygen their bodies used during strenuous exercise – a key factor of physical fitness. The men wore accelerometers for a week to measure their physical activity levels and had a detailed examination of their body size and composition.

Statistical modeling was used to find the extent to which composition and body size, fitness and physical activity variables could explain variations in insulin resistance and blood sugar between Europeans and South Asians.

The outcomes revealed that lower fitness, combined with greater body fat in South Asians, accounted for over 80% of their elevated insulin resistance compared to white men.

Dr Nazim Ghouri, of the Institute of Cardiovascular and Medical Sciences, who led the study with Dr Jason Gill and Prof Naveed Sattar, said, “Low fitness is the single most important factor associated with the increased insulin resistance and blood sugar levels in middle-aged South Asian compared with European men living in the UK.”

The data also suggested that while fitness gets better with more physical activity, South Asians’ lower fitness values could not be explained by just their lower activity levels.

South Asians showed lower fitness levels than Europeans at all levels of physical activity – implying that there are inherent variations in body make-up.

Dr Gill added:

“The fact that South Asians’ increased insulin resistance and blood sugar levels are strongly associated with their lower fitness levels, and that increasing physical activity is the only way to increase fitness, suggests that South Asians may need to engage in greater levels of physical activity than Europeans to achieve the same levels of fitness and minimise their diabetes risk.”

Prof Sattar then concluded:

“This has potential implications for physical activity guidance, which, at present, does not take ethnicity into account.

A number of leading doctors and scientists have already recommended that the BMI threshold for obesity in South Asian populations should be lowered from 30 kg/m2 to 25 kg/m2, in recognition of the fact that substantially lower BMIs are needed in South Asians to confer equivalent diabetes risk to those observed in populations of white European origin.

The present data suggest that differential physical activity guidance for South Asians may also be needed.”

A team from the University of Leicester, England, called for a lowering of the obesity limit for South Asians. They reported their findings in PLoS One (November 2011 edition).

Written by Kelly Fitzgerald