Abstract: Background: Elevated circulating branched chain amino acids (BCAAs; isoleucine, leucine and valine) are associated with obesity, and type 2 diabetes (T2D). Reducing circulatory BCAAs by dietary restriction was suggested to mitigate these risks in rodent models, but this is a challenging paradigm to deliver in humans. Aim: We aimed to design and assess the feasibility of a diet aimed at reducing circulating BCAA concentrations in humans, while maintaining energy balance and overall energy/protein intake. Method: Twelve healthy individuals were assigned to either a 7-day BCAA-restricted diet or a 7-day control diet. Diets were iso-nitrogenous and iso-caloric, with only BCAA levels differing between the two. Results: The BCAA restricted diet significantly reduced circulating BCAA concentrations by ~50% i.e. baseline 437±60 to 217±40 µmol/L (p<0.005). Individually, both valine (245±33 to 105±23µmol/L;p<0.0001), and leucine (130±20 to 75±13µmol/L;p<0.05), decreased significantly in response to the BCAA restricted diet. The BCAA restricted diet marginally lowered Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) levels: baseline 1.5±0.2 to 1.0±0.1; (p=0.096). Conclusion: We successfully lowered circulating BCAAs by 50% while maintaining iso-nitrogenous, iso-caloric dietary intakes, and while meeting the recommended daily allowances (RDA) for protein requirements. The present pilot study represents a novel dietary means by which to reduce BCAA, and as such, provides a blueprint for a potential dietary therapeutic in obesity/diabetes. Ethics: All participants gave written informed consent before inclusion in the study in accordance with the Declaration of Helsinki, and approved by University of Nottingham Ethics committee, refernce number 158-1711 approved on the 24th of November 2017.