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.”
Insulin, a hormone naturally produced by the pancreas, helps your body convert food into energy and regulate blood sugar levels. Everyone with type 1 diabetes, and many with type 2 diabetes, require insulin as a medicine to keep their blood sugar in check.
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.
Studies have consistently shown that insulin use is associated with weight gain. One large clinical trial found that type 1 patients who used intensive insulin treatment gained 10 pounds more than patients using less insulin, but the change in weight dissipates in long-term follow-up. Wadsworth says that insulin may also increase feelings of hunger and the perception of sweet flavors.
“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.
For generations, excessive weight gain was rarely considered a problem in the type 1 diabetes community. That’s because so many people with the condition experienced unintended weight loss, one of the reliable side effects of undiagnosed or uncontrolled type 1 diabetes.
Today, however, weight gain is an emerging problem for people with type 1 diabetes. Advances in diabetes care have made it easier than ever to approach normal blood sugar levels, which has reduced the frequency of unintended weight loss. As a result, people with type 1 diabetes have caught up to the general population and are now just as likely to be overweight or obese.
People with type 1 diabetes who are overweight or who have obesity are more likely to experience insulin resistance, which makes their condition more difficult to manage. In some cases it can even lead to “double diabetes,” the simultaneous coexistence of types 1 and 2 diabetes.
Another potential explanation for insulin weight gain among people with type 1 diabetes is the threat of hypoglycemia, a side effect of insulin. Low blood sugar events sometimes compel people with type 1 diabetes to overeat in order to get their blood sugar levels back up. The fear of low blood glucose events may also cause some patients to overeat.
“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.
And it’s a bad idea to skip insulin to keep that weight off. Intentionally using too little insulin in order to lose weight can lead to a diagnosable eating disorder nicknamed diabulimia. That is an extremely dangerous condition that can lead to cardiovascular disease, nerve damage, hospitalizations, and even death.
Excess weight is a major risk factor for type 2 diabetes, so people with this condition may worry that insulin could make them even heavier. Several other diabetes medications, such as sulfonylureas, have also been linked to weight gain.
There’s good reason to be concerned. Weight gain is a big problem for people with type 2 diabetes, as adding excess weight is highly associated with disease progression and a rising risk of complications.
As with type 1 diabetes, snacking to prevent or correct hypoglycemia can also contribute to overeating and therefore caloric excess and weight gain.
“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. “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 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. “SGLT2 inhibitors can lead to weight loss or stabilization, but not as much as the GLP-1 agonists,” says Retnakaran.
Drugs from these classes can be used alongside insulin to counteract insulin’s effect on weight, in addition to their other benefits.
“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.”
Though these drug classes are not officially indicated for the treatment of people with type 1 diabetes, some doctors have prescribed them off-label. Their use to treat type 1 diabetes is associated with weight loss and other benefits, but may also come with enhanced risks, making close collaboration with a doctor critical.
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
Whether you use insulin therapy or not, some eating approaches are better for weight maintenance than others. The American Diabetes Association recommends consuming a variety of nutrient-dense foods in appropriate portion sizes to improve health and achieve your body-weight goals. A diabetes-friendly diet with plenty of fiber and protein, and fewer refined carbohydrates, can reduce the amount of insulin you need to keep your blood sugar in a healthy range.
“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
Exercise is an effective way to help improve insulin sensitivity, allowing you to use smaller doses of insulin without risking blood sugar rises. Exercise also plays a big role in maintaining your weight, and getting 150 minutes of moderate intensity exercise a week is the recommended amount to improve blood sugar control.
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.
