I have had pups with elevated lipase and no symptoms. Being overweight does put a strain on the pancreas. I would definitely try to get the weight off of him. My George had a couple of bouts of pancreatitis when he was younger. He had an elevated lipase level about a year ago and I was concerned, but the vet was not overly concerned at the time. He was a bit overweight and has now lost the excess weight and his levels are fine.
As EllieMay said, more specific tests are usually done. Perhaps this link may help you:
Canine Pancreatitis