It is not uncommon for people with type 2 diabetes who begin insulin therapy to gain weight; studies have shown that decreasing HbA1c levels by 2.5% is associated with a gain of 5 kg, or 11 pounds, in a year.

Since most people with type 2 diabetes are already overweight, this creates an additional dilemma. However, a new study from Finland suggests that such weight gain can be avoided if metformin is given with insulin.

Ironically, it is the person who has poor glycemic control before starting insulin and then responds well to insulin - i.e., achieves good glycemic control - who is most likely to gain weight. That is because in people with poor glycemic control, energy is used to produce more glucose; when control is better, less energy is used and weight increases. Also, when blood sugar levels are high, much of the extra glucose leaves the body in urine - as much as several hundred calories a day may be lost that way. With better glucose control, those calories stay in the body; and, if hypoglycemia occurs, even more calories are consumed in the sweets used to treat low blood sugar. Better glucose control also decreases metabolic rate and, if dietary intake doesn’t change, weight gain will result.

So if you are starting on insulin therapy, eat less food and ask your doctor about combination therapy with metformin to minimize your chance of gaining weight.

While this study focused on type 2 diabetes, the issue of weight gain with insulin also affects people with type 1 diabetes.

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