In common with many other low- and middle-income countries (LMICs), rural to urban migrants in India are at increased risk of obesity, but it is unclear whether this is due to increased energy intake, reduced energy expenditure, or both. Knowing this and the relative contribution of specific dietary and physical activity behaviours to greater adiposity among urban migrants could inform policies for control of obesity epidemic in India and other urbanising LMICs. In the Indian Migration Study, we previously found that urban migrants had greater prevalence of obesity and diabetes compared to their non-migrant rural-dwelling siblings. In this study, we investigated the relative contribution of energy intake and expenditure, and specific diet and activity behaviours, to greater adiposity among urban migrants in India.
Methods and findings
The Indian Migration Study was conducted between 2005 and 2007. Factory workers and their spouses from four cities in north, central and south of India, together with their rural-dwelling siblings, were surveyed. Self-reported data on diet and physical activity was collected using validated questionnaires and adiposity was estimated from thickness of skinfolds. The association of differences in dietary intake, physical activity and adiposity between siblings was examined using multivariable linear regression. Data on 2464 participants (median age 43 years) comprised of 1232 sibling pairs (urban migrant and their rural-dwelling sibling) of the same sex (31% female) were analysed. As compared to the rural siblings, urban migrants had 18% greater adiposity, 12% (360 calories/day) more energy intake and 18% (11 kilojoules/kg/day) less energy expenditure (P<0.001 for all). Energy intake and expenditure were independently associated with increased adiposity of urban siblings, accounting for 4% and 6.5% of adiposity difference between siblings, respectively. Difference in dietary fat/oil (10g/day), time spent engaged in moderate or vigorous activity (69 minutes/day) and watching television (30 minutes/day) were associated with difference in adiposity between siblings, but no clear association was observed for intake of fruits and vegetables, sugary foods and sweets, cereals, animal and dairy products, and sedentary time. The limitations of this study include a cross-sectional design, systematic differences in pre-migration characteristics of migrants and non-migrants, low response rate, and measurement error in estimating diet and activity from questionnaires.
We found that increased energy intake and reduced energy expenditure contributed equally to greater adiposity among urban migrants in India. Policies aimed at controlling the rising prevalence of obesity in India and potentially other urbanising LMICs need to be multi-component and target both energy intake and expenditure, and focus particularly on behaviours such as dietary fat/oil intake, time spent on watching television and engaged in moderate or vigorous intensity physical activity.