Higher total adiposity (body fatness) is known to harm health. Studies tend to observe that adiposity stored centrally in the abdominal region is most strongly linked with factors which trigger type 2 diabetes and heart disease, but this has been little examined within a causal framework and so the relative importance of central vs total adiposity for disease risk is still uncertain. This study aims to harness the unique strengths of ALSPAC to examine whether higher central adiposity (indicated through higher waist-to-hip ratio) is likely to cause cardiometabolic trait levels in childhood and young adulthood. Of particular interest is whether effects of higher central adiposity get stronger with the amount of time exposed, and whether they are stronger than effects of total adiposity (indicated through body mass index). Causal methods of Mendelian randomisation will be used at both life stages (childhood and young adulthood), and outcomes will include an extensive set of blood-based cardiometabolic traits through novel targeted metabolomics. Altogether, this study aims to provide deeper insight into the causal impact of central adiposity on cardiometabolic health than ever before.