ABSTRACT: Abstract The recent International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome (PCOS) recommended healthy lifestyle interventions (dietary, exercise, behavioral modification, or combined) as the first-line therapy to mediate favorable metabolic outcomes in PCOS. However, the relationship between lifestyle modifications and reproductive health in PCOS is less clear. Specifically, a favorable dietary composition to facilitate reproductive changes in women with PCOS remains unknown. Further, the longitudinal impacts of lifestyle change programs in women with PCOS is poorly elucidated. We hypothesized that a low glycemic index pulse-based diet containing lentils, beans, split peas, and chickpeas would be more effective than the Therapeutic Lifestyle Changes (TLC) diet at improving insulin sensitivity without an energy-restricted protocol and would improve reproductive health outcomes in women with PCOS after a 16-week intervention. Our objective was to compare the effects of a nutritionally balanced pulse-based diet with the TLC diet on ultrasonographic markers of ovarian morphology, hyperandrogenism, and menstrual irregularity. Women (n=30) randomized to the pulse-based and TLC (n=31) groups completed a 16-week intervention. All women participated in aerobic exercise (minimum 5 days/week; 45 minutes/day) and received health counseling (monthly) about PCOS and the benefits of lifestyle modification. Additionally, we evaluated the effects of the intervention on the reproductive outcomes by longitudinal follow-up of all participants. Follicle numbers per ovary (FNPO, 2-9 mm), ovarian volume (OV), free androgen index (FAI), intermenstrual intervals, and insulin sensitivity (Matsuda index and homeostasis model assessment of insulin resistance [HOMA-IR] were evaluated at baseline, 16-week post-intervention, and 6- and 12-month post-intervention follow up visits. Follicle numbers per ovary (mean change ± SD, -10 ± 15), OV (-2.7 ± 4.8 mL), FAI (-3 ± 2), intermenstrual interval (-13 ± 47 days), and body mass index (BMI, -1.6 ± 4.2 kg/m2) decreased, and Matsuda index (1.1 ± 3.1) increased over time in both groups (All: P ? 0.01), without group-by-time interactions (All: P ? 0.27). Groups maintained reduced OV, FNPO, FAI, and menstrual cycles 6 months post-intervention, despite a propensity for weight regain as evidenced by increased BMI (1.0 ± 4.8 kg/m2; P < 0.01). Decreased FNPO, FAI, and HOMA-IR at 16-week tended to revert to baseline levels 12 months post-intervention in both groups (All: P ? 0.05). Both interventions improved ovarian dysmorphology, hyperandrogenism, and menstrual irregularity in women with PCOS. Our observations elucidate the importance of longitudinal surveillance for sustainable adherence to newly adopted healthy lifestyle behaviors and reproductive health in PCOS (ClinicalTrials.gov identifier, NCT01288638).