Insulin Resistance and Cardiorespiratory Fitness : Ethnic Differences

MedicalResearch.com Interview with:
Dr Nazim Ghouri MBChB, MRCP UK
Specialty Registrar (Diabetes/Endocrinology/GIM) and Honorary Clinical Lecturer
Institute of Cardiovascular and Medical Sciences
BHF Glasgow Cardiovascular Research Centre
University of Glasgow
Glasgow G12 8TA

Lower cardiorespiratory fitness contributes to increased insulin resistance and fasting glycaemia in middle-aged South Asian compared with European men living in the UK

MedicalResearch.com: What are the main findings of the study?

Answer: In this study we aimed to determine the extent to which increased insulin resistance and blood sugar levels in South Asian men, compared to white European men, living in the UK, was due to lower fitness and physical activity levels.

We studied 100 South Asian and 100 European men aged 40-70 years living in Scotland without diagnosed diabetes and measured their blood sugar levels, insulin resistance and other risk factors.

The men also undertook a treadmill exercise test to determine how much oxygen their bodies were able to use during intense exercise – a key measure of physical fitness, wore accelerometers for a week to assess their physical activity levels, and had a detailed assessment of their body size and composition. Statistical modeling was then used to determine the extent to which body size and composition, fitness and physical activity variables explained differences in insulin resistance and blood sugar between South Asians and Europeans.

The results suggested that lower fitness, together with greater body fat in South Asians, explained over 80 per cent of their increased insulin resistance compared to white men with Low fitness being the single most important factor associated with the increased insulin resistance and blood sugar levels in middle-aged South Asian compared to European men living in the UK.

MedicalResearch.com: Were any of the findings unexpected?

Answer: The data also showed that while fitness improves with increasing physical activity, South Asians’ lower fitness values could not be explained simply by their lower activity levels. South Asians had lower fitness levels than Europeans at all levels of physical activity, suggesting inherent differences in body make-up.

MedicalResearch.com: What should clinicians and patients take away from your report?

Answer:  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 minimize their diabetes risk.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Answer:  These findings have potential implications for physical activity guidance, which, at present, do 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.

Citation:

Lower cardiorespiratory fitness contributes to increased insulin resistance and fasting glycaemia in middle-aged South Asian compared with European men living in the UK.

Ghouri N, Purves D, McConnachie A, Wilson J, Gill JM, Sattar N.

BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK,
Diabetologia. 2013 Jun 29.
[Epub ahead of print]