Does Insulin Cause Weight Gain?

Many people with diabetes need to use insulin to manage their blood sugar. But this vital medication often has a frustrating side effect: weight gain.

When people with type 1 or type 2 diabetes are prescribed insulin, it’s common for them to put on some extra pounds, says Tom Wadsworth, PharmD, the dean and an associate professor at L.S. Skaggs College of Pharmacy at Idaho State University in Pocatello. “However,” Dr. Wadsworth says, “it’s not inevitable, and some patients successfully prevent or even lose weight with the right strategies.”

One of the other primary functions of insulin is to facilitate fat storage, which is where weight gain can come into play.

“Insulin's job is to help store energy, so when someone eats more calories than they burn — especially in response to low blood sugar or increased appetite — the body is more likely to store fat instead of burning it,” says Wadsworth.

“Insulin can stimulate appetite, especially when blood sugar levels drop,” he says. “Some people also experience increased cravings for sweet or high-calorie foods, as insulin plays a role in reward and taste perception in the brain.”

The type of insulin you take may be more likely to cause weight gain than other types.

“The rapid, short, and intermediate acting insulins have been associated with the most weight gain, while longer-acting formulations tend to cause less weight gain — though they can still contribute to it,” says Ravi Retnakaran, MD, a professor of medicine at the University of Toronto.

“Some people are understandably fearful of hypoglycemia and its implications, so they try to keep their blood sugars elevated by eating, and doing so, you’re getting excessive calories that can contribute to weight gain,” says Dr. Retnakaran.

“Weight gain is largely driven by calorie intake and metabolic shifts. Careful insulin dose adjustments, meal planning, and regular activity can minimize or even prevent weight gain,” says Wadsworth.

In recent years, two newer families of type 2 diabetes drugs have made it easier to find glucose-lowering treatments that spur weight loss instead of weight gain.

• GLP-1 and dual GIP/GLP-1 receptor agonists, including semaglutide (Ozempic) and tirzepatide (Mounjaro), have a potent glucose-lowering effect and are proving to be very effective weight loss drugs for many who take them.

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   “They have been game changers in the management of type 2 diabetes,” says Wadsworth. GLP-1s promote weight loss by reducing appetite and keeping your stomach full longer, among other factors. “Type 2 patients can lose up to 25 percent

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   of their body weight within a year, which greatly reduces their insulin-resistance, precluding the need for insulin therapy.”
• SGLT2 inhibitors, including empagliflozin (Jardiance) and dapagliflozin (Farxiga), lower blood sugar levels and protect kidney and heart health while inducing modest weight loss.

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   “SGLT2 inhibitors can lead to weight loss or stabilization, but not as much as the GLP-1 agonists,” says Retnakaran.

“Both drug classes have become preferred options for managing type 2 diabetes, especially in obese patients or those at risk of weight gain, particularly when insulin therapy is required,” says Wadsworth. “More importantly, these medications offer significant cardiovascular and kidney benefits, reducing the risk of heart attacks and other serious diabetes-related complications — benefits that insulin therapy does not provide.”

It’s dangerous to reduce or adjust insulin dosing without consulting a doctor first. Talk to your medical team about the interactions between your insulin dosage and your diet, exercise habits, and other medications. Weight gain is not inevitable. “Balancing insulin dosing and meal timing can help reduce that effect,” says Wadsworth. Here are other healthy lifestyle tips to help you keep the scale at the weight you want.

Eat Healthier

“I always have my patients see a dietitian, so they are following healthy dietary patterns,” says Retnakaran. “A dietitian can work with you to optimize your eating in the context of your preferences and give you healthy suggestions.”

Sometimes, when we feel hungry, we may just be thirsty. Choose water, and you’ll take an essential step toward being hydrated and feeling fuller. It’s a healthy beverage that won’t spike your blood glucose levels like sugary sodas or sweetened fruit juice.

Exercise Regularly

Ask About Adjusting Your Medications

If you have type 2 diabetes, ask your healthcare provider about potentially switching to GLP-1 or SGLT2 drugs, which can cause weight loss — instead of weight gain — and lower your blood glucose levels.

“These drugs can help offset the weight gain caused by insulin, and in most cases of type 2 diabetes, can be used to help patients avoid insulin therapy altogether," says Wadsworth.

• Insulin therapy is essential for many people who have diabetes, but it often leads to weight gain due to the hormone’s role in fat storage.
• Weight gain is not inevitable if you take insulin. A healthy diet and a commitment to regular exercise can improve your insulin sensitivity and reduce your need for extra insulin, potentially slowing, preventing, or reversing weight gain.
• Other type 2 diabetes medicines that have a weight loss effect, like GLP-1 receptor agonists and SGLT2 inhibitors, may be alternatives or additions to insulin therapy that can counteract weight gain.

Additional reporting by Jessica Freeborn.