Higher than normal body mass index (BMI) is known to cause cardiovascular diseases in mid-to-late life but a new research has revealed a higher BMI can cause worse cardiovascular health even in those aged as young as 17. The researchers from University of Bristol UK hypothesised that cardiovascular risk due to increased BMI was likely to emerge in earlier life. Our results showed that the causal impact of higher BMI on cardiac output was solely driven by the volume of blood pumped by the left ventricle. This at least in part can explain the causal effect of higher BMI on