Insulin and Weight Gain?

Q: I take insulin and it's very hard for me to lose weight. I've read that this can happen — that insulin can contribute to weight gain. What can I do? I try to watch what I eat and have recently joined a fitness club, but I haven't had much success yet. Any advice?

— Susan

A:Insulin can, in fact, lead to weight gain. Here's how it works:
Insulin is a potent hormone that regulates glucose, fat, and protein metabolism. In many cases, people with type 2 diabetes start insulin therapy when oral medicines cannot or no longer control their glucose levels. This means that blood glucose levels in the body have been elevated for an extended period of time. In this state, the body does not metabolize glucose, fat, or protein in a well-regulated or efficient way. Cells that require glucose to function properly begin starving because of inadequate amounts of circulating insulin. Fat metabolism becomes abnormal, which can lead to high triglyceride levels. The body's metabolic rate then increases as it tries to convert this fat into a source of energy.

These abnormalities are usually corrected when you begin insulin therapy. The body begins using glucose better, and the metabolic rate declines by about five percent. Insulin also helps the body gain fat-free mass, but on the flip side, it also helps it store fat more efficiently. Therefore, efficient glucose and fat metabolism and the reduction in metabolic rate cause most people to gain four to six pounds during the first two to three years of insulin therapy. Individuals who had poor glucose control, or who lost significant amounts of weight before beginning insulin treatment, usually experience the most weight gain.

Losing weight in general requires persistent attention to energy balance — that is, the number of calories you take in versus the number you burn. During insulin therapy, the body does not need as much food to get the energy it requires, so reducing your caloric intake is quite important. This should be accompanied by an exercise regimen, as you have begun, to expend at least 200 to 300 calories a day.

In addition, you should consult with your doctor to consider other kinds of diabetes treatments that could mitigate the weight gain. These include metformin, an oral medication that prevents weight gain; an insulin analogue called detemir, which has been shown to cause less weight gain than NPH insulin; and exenatide, an antidiabetes injection that can lead to weight loss.