The study found that those who lost 10 percent or more of their body weight had an 85 percent lower risk of developing diabetes within three years, while those who lost 5 percent to 7 percent of their body weight had a 54 percent lower risk.
The findings offer patients and doctors a guide to how short-term behavior change may affect long-term health, the researchers said.
"We have known for some time that the greater the weight loss, the lower your risk of diabetes," study leader Dr. Nisa Maruthur, an assistant professor in the division of general internal medicine at the Johns Hopkins University School of Medicine, said in a Hopkins news release.
"Now we understand that we can see much of the benefit of losing that weight in those first six months when people are adjusting to a new way to eating and exercising," Maruthur said. "Substantial weight loss in the short term clearly should go a long way toward preventing diabetes."
The study included more than 3,000 patients who were assigned either to be part of a lifestyle intervention group, or to take the diabetes drug metformin, or to take a placebo. Metformin is taken to lower blood sugar levels.
The patients all had pre-diabetes, which means their blood sugar levels were higher than normal but not yet high enough to be considered type 2 diabetes.
Those in the lifestyle intervention group were given advice about healthy eating, told to exercise 150 minutes a week, and given one-on-one counseling for the first six months and group counseling for the remainder of the three-year study.
While the patients who took metformin did not lose significant amounts of weight, their blood sugar levels were significantly lower after six months and they did have a lower risk of developing diabetes.
The lowest risk of diabetes was seen in patients who lost weight and also lowered their blood sugar levels, according to the study published online July 16 in the Journal of General Internal Medicine.
The American Academy of Family Physicians has more about pre-diabetes.