For people with Type 1 diabetes, weight gain may actually be a positive, new research suggests.

Though excessive weight gain is one of the risk factors for Type 2 diabetes, a 20-year study of 658 patients with Type 1 diabetes found that those who gained the most weight, an average of 10 to 55 pounds or a body mass index increase of between 2 and 11 points, were one-third less likely to die than those with smaller BMI increases.

The study participants, who were an average age of 28 at the beginning of the study and 44 when it ended, were diagnosed with Type 1 diabetes between 1950 and 1980. Over the 20-year study period, 147 of them died.

The researchers believe that weight gain may have a protective effect for Type 1 diabetics.

"Although weight gain in adulthood is typically associated with increased mortality, this may not be the case for those with Type 1 diabetes," said Trevor Orchard, professor of epidemiology at the University of Pittsburgh Graduate School of Public Health, in a release.

"Gaining a reasonable amount of weight may be a sign patients are getting enough insulin and appropriately controlling their disease, which may partly explain why those who gained weight over time had lower mortality rates."

The study also found that those participants with a normal BMI of between 20 and 25 and those with a BMI in the overweight range (25 to 30) had no differences in mortality.

However, participants who had an underweight BMI of less than 20 were much more likely to die prematurely.

The researchers caution that gaining weight with Type 1 diabetes is not advised as a protective measure, but they feel the findings cast a new light on weight recommendations for people with the disease.

The study was presented Friday at the 68th Scientific Sessions of the American Diabetes Association in San Francisco.