OBJECTIVE: Studying physiologic underpinnings of loss-of-control (LOC) eating may inform its etiology and contribute to intervention efforts. We therefore examined temporal relationships between autonomic indices [heart rate (HR), heart rate variability (HRV)] and LOC-eating in the natural environment. METHOD: For two days, adolescents (n = 17, 14.77 +/- 1.55 years, BMI-Z 2.17 +/- 0.48) with LOC-eating reported on LOC using an electronic device while HR and HRV were assessed continuously using Holter monitoring. RESULTS: Higher HR and lower HRV in the 30-minutes before eating were significantly associated with LOC-eating overall (p\'s < 0.001) and at the within-participants level (p\'s < 0.001), but not at the between-participants level (p\'s > 0.44). Examined categorically, HR was significantly higher, and HRV significantly lower, prior to high-LOC compared to low-LOC episodes (p\'s < 0.001). DISCUSSION: This pilot study suggests that LOC-eating may involve physiologic underpinnings. Additional research with larger samples is needed to further investigate this phenomenon.