The study, funded by the British Heart Foundation (BHF), looked at the levels of physical activity of 2,000 children living in the UK aged between nine and 10 years from Birmingham, London and Leicester.
It found that British South Asian children are less active than black African-Caribbean and white European children of the same age.
Experts say the finding could hold the key to explaining the higher levels of heart and circulatory disease and type 2 diabetes amongst the South Asian population.
Dr Christopher Owen, senior lecturer in epidemiology at St George's, University of London, who led the study, said: "Increasing levels of physical activity in children of South Asian origin may be particularly important in helping to maintain their health in the longer term."
Dr Mike Knapton, associate medical director at the BHF said: "This study is another piece in the jigsaw in helping us to understand why British South Asians are at higher risk of cardiovascular disease and type 2 diabetes. We now need to explore how we can lessen their risk of these conditions by increasing exercise levels."
