The pilot stated, after takeoff the engine sputtered and began losing power during initial climb. According to the pilot, he tried to land on a highway but there were numerous vehicles in transit and he decided to attempt an off-airport landing. On initial impact with the right wing, the aircraft tore off a branch from a tree, then struck a grassy knoll with the right wing tip. Main impact occurred with a branch of a second tree and the aircraft came to rest inverted. Post accident calculations revealed that the aircraft was 67 pounds over the max allowable gross weight, and within the C.G. range during takeoff. A subsequent engine teardown inspection revealed no preexisting condition, malfunction, or abnormal wear. According to witnesses at the airport, the pilot was observed attempting to remove frost from the wings and was running the engine at idle for almost 30 minutes before takeoff was initiated. Carburetor heat was found in the off position.