Health professionals generally recommend diets including plenty of whole fruits, wholegrains, fibre-rich vegetables, pulses, legumes and nuts based on high quality evidence showing an inverse relationship between these foods and risk of chronic disease. However, these recomendations are being challenged by advocates of low carboyhdrate diets. Much of the controversy arises due to the comparison of low carbohydrate diets with high carbohydrate diets that include large amounts of highly refined carbohydrates, including sugars. Thus, there is an urgent need to better understand how different types of carbohydrate sources affect health outcomes. The aim of this research is to conduct a systematic review and meta-analyses of randomised trials and cohort studies involving children and adults that have investigated the effect of different types of dietary carbohydrates on obesity, diabetes, cardiovascular disease and their established risk factors. These findings will inform international and national dietary recommendations which are currently pending updates.