The present invention provides a body lift-assist walker device for gait training is provided by the invention. The patient wears a pressurized body suit over all or a portion of his lower body, and the suit is attached to the walker device. A positive pressure or vacuum condition is applied to the interior of the suit, so that the differential pressure condition across the suit offloads a portion of the patient's body weight to the ground through the supportive walker device to make it easier for him to walk or run. The walker device also includes a lift-assisted body weight support device operated by a constant force mechanism like a pneumatic air cylinder that can lift the patient from a sitting position to a standing position with minimal physical effort. The device provides a portable and convenient system for persons undergoing physical therapy for treatment of gait or balance problems following an injury, stroke, or neurological disorder, or for use by elderly or disabled persons who have encounter difficulties in the sit-to-stand movement or walking.