Obese patients with gastroesophageal reflux disease (GERD) may experience resolution of symptoms utilizing a very low-carbohydrate diet. The mechanism of this improvement is unknown. This studied aimed to prospectively assess changes in distal esophageal acid exposure and GERD symptoms among obese adults initiating a very low-carbohydrate diet. We studied obese individuals with GERD initiating a diet containing less than 20 g/day of carbohydrates. Symptom severity was assessed using the GERD Symptom Assessment Scale--Distress Subscale (GSAS-ds). Participants underwent 24-hr esophageal pH probe testing and initiated the diet upon its completion. Within 6 days, a second pH probe test was performed. Outcomes included changes in the Johnson-DeMeester score, percentage total time with a pH<4 in the distal esophagus, and GSAS-ds scores. Eight participants were enrolled. Mean Johnson-DeMeester score decreased from 34.7 to 14.0 (P=0.023). Percentage time with pH<4 decreased from 5.1% to 2.5% (P=0.022). Mean GSAS-ds score decreased from 1.28 to 0.72 (P=0.0004). These data suggest that a very low-carbohydrate diet in obese individuals with GERD significantly reduces distal esophageal acid exposure and improves symptoms.