Patients with type 1 diabetes who take multiple insulin injections each day may lower their risk of nerve damage and blindness, but such intensive therapy may also put them at increased risk of obesity.

According to researchers, adults who treated their disease with multiple daily insulin injections or continuous infusion were more likely to become overweight after 6 years.

This group gained an average of 9.5 pounds more than patients who took one or two insulin shots a day. The weight gain translated into an increase in body mass index (BMI) of 1.5 for men and 1.8 for women.

BMI, which takes into account a person's weight in relation to their height, is considered a more accurate measure of overweight and obesity than body weight alone. A person with a BMI of at least 25 is considered overweight and one with a BMI of 30 and above is considered obese.

Previous research has shown that intensive insulin therapy can lower the risk of some of the medical complications associated with type 1 diabetes. However, it may also lead to severe hypoglycemia -- a significant drop in blood sugar -- and weight gain.

The results show that weight gain was most rapid in the first year. Although the rate of weight gain slowed in subsequent years, patients did not shed any pounds, even after 9 years. Women tended to put on weight at a faster rate than men did, and women treated intensively tended to gain weight in their abdomens.

Abdominal obesity, the authors note, is believed to be a risk factor for heart disease.

Intensive therapy for type 1 diabetes produces substantial excess weight gain compared with conventional therapy. However, the additional weight appears to include lean tissue as well as fat.

Diabetes Care October 2001;24:1711-1721