A randomized trial of 112 young adults with overweight or obesity found that a personalized whole-food diet intervention produced differential metabolic effects by race. Black participants showed greater reductions in fasting insulin levels and improved early glucose handling compared to White participants, while both groups experienced enhanced cognitive concentration performance versus conventional dietary counseling using MyPlate guidelines over 8 weeks. The personalized intervention also improved pancreatic beta-cell function (lower HOMA-β) across all participants and boosted processing speed and accuracy more substantially in Black adults. This finding addresses a critical gap in nutrition research, as most dietary trials have historically enrolled predominantly White cohorts despite Black adults facing disproportionately higher rates of diabetes and cardiovascular disease. The differential insulin response suggests potential genetic or metabolic variations in how racial groups respond to whole-food interventions, though the relatively small sample size and short duration limit broader conclusions. As a preprint awaiting peer review, these results require validation through the peer-review process before clinical implementation. The study represents an important step toward personalized nutrition approaches that account for racial differences in metabolic health responses.