There have been no studies that were able to demonstrate that wearing a back belt will help prevent back pain, hence the gradual disappearance of those belts worn in the workplace mentioned in the introductory paragraph. In fact, some studies have shown that people wearing a belt will actually believe they are better protected while wearing one, place less importance on proper lifting, and actually increase the likelihood of injury. To prevent back pain, the best way to increase stability is to increase core strength, a major emphasis by both chiropractors and physical therapists when treating low back pain.

More details in this article dedicated to the question of back belts.