Maintaining a lower body mass index (BMI) can help reduce the risk of developing ischemic heart disease (IHD), say researchers. BMI, alongside age, smoking, diabetes, high blood pressure, high blood cholesterol levels, and individuals who have family history of the disease, hasbeen long recognised as a risk factor for heart disease. Despite this, the actual causal contribution of BMI to disease risk has been difficult to quantify. A new research that evaluated the causal relationship between BMI and heart disease in 76,000 individuals have revealed that an elevation in BMI of around 4kg/m2 across the life-course will increase the risk of developing the disease by 50 per cent on average. The findings resulted from a collaborative effort between the Medical Research Council (MRC) Centre for Causal Analyses in Translational Epidemiology (CAiTE) at the University of Bristol and colleagues from Copenhagen University Hospital. Using genetic data from three large Danish studies - the Copenhagen General Population Study, the Copenhagen City Heart Study and the Copenhagen Ischemic Heart Disease Study - the researchers were able to use genetic variation known to be related to BMI to measure the true causal effect between this and IHD. In observational estimates, the researchers found that for every 4 kg increase in BMI a 26 per cent increase in odds for developing IHD, while causal analysis identified a 52 per cent increase. "In light of rising obesity levels, these findings are fundamental to improving public health. Our research shows that shifting to a lifestyle that promotes a lower BMI (even if it does nothing else) will reduce the odds of developing the disease," said Dr Timpson, Lecturer in Genetic Epidemiology from the University's School of Social and Community Medicine. Professor Borge Nordestgaard, lead author of the study from the University of Copenhagen, added: "These findings are of key importance, as obesity linked to diabetes is the only major cardiovascular risk factor on the rise in North America and Europe, while smoking, cholesterol levels and hypertension have been decreasing."