Devices and methods are provided for ablational treatment of regions of the digestive tract in post-bariatric surgery patients who fail to achieve or maintain the desired weight loss. Bariatric procedures include Roux-en-Y gastric bypass, biliopancreatic diversion, and sleeve gastrectomy. These procedures reconstruct gastrointestinal tract features, creating pouches, stoma, and tubes that restrict and/or divert the digestive flow. Post-surgical dilation of altered structures is common and diminishes their bariatric effectiveness. Ablation of compromised structures can reduce their size and compliance, restoring bariatric effectiveness. Ablation, as provided the invention, starts at the mucosa and penetrates deeper into the gastrointestinal wall in a controlled manner. Control may also be provided by a fractional ablation that ablates some tissue within a target region and leaves a portion substantially unaffected. Embodiments of the device include an ablational electrode array that spans 360 degrees and an array that spans an arc of less than 360 degrees.