The recently famous weight loss surgery, a remedy for T2 diabetes, is not effective as expected according to a new study report. The study found that many obese Type 2 diabetics who undergo gastric bypass surgery do not experience a remission of their disease and also a third redevelop diabetes within five years of their operation.

The study, published in the journal Obesity Surgery, tracked thousands of diabetics who had gastric bypass surgery for more than a decade. It found that many people whose diabetes at first went away were likely to have it return. While weight regain is a common problem among those who undergo bariatric surgery, regaining lost weight did not appear to be the cause of diabetes relapse. Instead, the study found that people whose diabetes was most severe or in its later stages when they had surgery were more likely to have a relapse, regardless of whether they regained weight.

The findings suggest that weight loss surgery may be most effective for treating diabetes in those whose disease is not very advanced. “What we’re learning is that not all diabetic patients do as well as others,” said Dr. David E. Arterburn, the lead author of the study and an associate investigator at the Group Health Research Institute in Seattle. “Those who are early in diabetes seem to do the best, which makes a case for potentially earlier intervention.”