An inverted J–shaped relationship between coronary flow reserve and body mass index is illustrated using a restricted cubic spline linear regression model with 95% confidence intervals (orange); patient frequency histograms are shown for body mass index (blue). Model is adjusted for demographic and clinical risk factors (age, sex, race, hypertension, diabetes, peripheral vascular disease, chronic obstructive pulmonary disease, atrial fibrillation, tobacco use, estimated glomerular filtration rate, beta-blocker use, and left ventricular ejection fraction).