Insulin and Weight Gain: Understanding the Connection

Insulin is a commonly used medication to treat patients with both type 1 and type 2 diabetes. Weight gain is a commonly seen side effect. Patients may have questions about insulin and potential weight gain out of concern for their appearance or their health (or both). According to a 2007 paper in Diabetes Obesity Metabolism, “This weight gain can be excessive and, adversely affect cardiovascular risk profile.”

If patients gain weight on insulin, they may become frustrated with their treatment. They may even resist starting insulin therapy because of anecdotal information they’ve heard about gaining weight on insulin. It’s helpful to understand the connection and how to talk to patients about it.

Why Does Insulin Cause Weight Gain?

Exogenous insulin can worsen hyperinsulinemia in patients with type 2 diabetes and high insulin resistance. Insulin resistance is a condition wherein glucose is not easily stored as glycogen. Glucose is preferentially converted to fat via increased de novo lipogenesis. This then contributes to increased adiposity and weight gain. Hypoglycemia per se can elicit hunger and induce eating (MacKay et al. 1940; Lotter & Woods 1977), the best-characterized behavioral effect of insulin administration is increased food intake resulting from insufficient glucose reaching the brain.

People with diabetes may also tend toward overeating out of fear of a hypoglycemic episode, sometimes called “defensive snacking.” In either type of case, patients may benefit from nutritional counseling or other assistance with food choices.

Other possible causes of exogenous insulin-caused weight gain include a false sense of freedom to eat, regaining weight previously lost due to diabetes, and genetic factors.

How Much Weight Could a Patient Gain on Insulin?

The amount of weight gain can vary with the patient. In one study, researchers followed 2,179 people for one year, collecting data on body weight change and potential predictive factors. Their findings were published in Diabetes Care. The mean weight gain for the study participants was 1.78 kg, and 24% of them gained at least 5.0 kg. A high baseline A1C and insulin dose requirements were independently associated with greater weight gain, as was a lower baseline BMI.

A study published in Diabetes Obesity Metabolism looked at insulin-associated weight gain in patients with type 2 diabetes. The researchers state, “A 3 to 9 kg insulin-associated weight gain is reported to occur in the first year of initiating IT, predominantly caused by adipose tissue.”

How Different Types of Insulin Impact Weight Gain

The type of insulin prescribed might make a difference in weight gain. There is some evidence that using basal insulin analogs may carry less risk of weight gain compared with conventional human insulin preparations. These insulins have a relatively flat time‐action profile and less risk of nocturnal hypoglycemia. Among basal insulin analogs, less weight gain occurs with insulin detemir (brand name Levemir) than with insulin glargine (brand names Lantus Solostar, Basaglar KwikPen, and Toujeo SoloStar), at least according to one study.

How To Help Patients Manage Insulin-Related Weight Gain

When treating a patient with diabetes using insulin, it is important to be mindful of changes in their weight. There are several ways to help support them in achieving greater success.

Set Expectations for a Patient Starting Insulin

Talk to patients about the possibility of weight gain and help them understand why it can happen. Exercise empathy to understand why this possibility may concern them.

Educate Patients on Diet and Exercise

Help them understand the role that diet and exercise play in their diabetes treatment and how to make choices most likely to support their success. Provide guidance on what types of food to eat and when. For exercise, the American Diabetes Association recommends a combination of aerobic activity and strength training.

Stress the Importance of Following the Treatment Plan

It is highly important that the patient take their medication as directed by their endocrinologist. They should never cut back or stop their insulin regimen without consulting a doctor.

Combine Insulin with Other Medications When Appropriate

It is not unusual for a person with diabetes to take multiple medications. For example, metformin is generally well tolerated and is associated with weight loss. A GLP-1 agonist may also be considered in some cases. The addition of another medication may affect the needed dose of insulin, so dosing should be carefully reviewed and monitored.

FAQs on Insulin and Weight Gain

Why is it hard to lose weight on insulin?

When a patient starts any exogenous insulin therapy, they need to learn how it affects their lifestyle, their hunger, and their eating habits. An eating plan high on refined carbohydrates and low in complex carbohydrates or fiber can increase glucose and insulin spikes which can make a patient feel more hungry causing them to eat more. Additionally, they may practice defensive eating to guard against hypoglycemic episodes.

What is the impact of blood glucose levels on body weight in patients with diabetes?

Blood glucose levels are intricately linked with body weight and a tendency toward obesity. When treating diabetes or obesity, blood glucose levels should be considered. Helping a patient to make dietary choices that support more consistent glucose and optimum caloric intake can benefit both their weight and their blood sugar.

Can insulin be used in combination with GLP-1 agonists?

Drug information on Wegovy and Ozempic states that these medications may increase the risk of hypoglycemia when used with exogenous insulin therapy. That does not mean a patient cannot use both. According to a paper published in the journal Drugs:

“Basal insulin can be added to a GLP-1 receptor agonist with slow titration to target goal fasting plasma glucose. In patients starting a GLP-1 receptor agonist, the dose of basal insulin should be decreased by 20 % in patients with an HbA1c ≤8 %.”

Learn More with OMA

To learn and keep pace with new understandings of diabetes and its treatment, join the Obesity Medicine Association. The OMA offers numerous resources for physicians and other medical practitioners seeking the latest research about obesity and related health factors.