At 1110 central time, a Cessna 177RG lost engine power and was damaged in the forced landing that followed. The pilot was not injured. The pilot reported he had taken off about five minutes earlier when the engine started to lose power. The pilot turned the airplane back toward the airport. The engine regained power and the pilot elected to continue the flight. Approximately 25 minutes later, while cruising at 3,000 feet msl, the engine gradually lost power. Unable to restart the engine, the pilot initiated a forced landing to a field, whereupon the airplane struck a ditch, flipped over and came to rest inverted.