You may have heard that insulin causes weight gain. Because of this, some people believe that being prescribed insulin may cause them to gain undesired weight. Let’s look at where this line of thought comes from and whether it is really true.

It is well-established that one of the primary functions of insulin is to facilitate fat storage. Of course, this should only occur when there is enough energy to store. When the calories consumed exceed the needs to fuel the numerous physiological processes our body performs every day, excess energy is stored as fat.

We must remember that every human and animal on earth needs insulin to survive and thrive. For those without diabetes, the pancreas efficiently pumps out the amount of insulin required to keep blood glucose levels normal around the clock, and in response to numerous variables, like meals or stress. Everyone has insulin in their system, regardless of diabetes.

Is there something different about using exogenous insulin as opposed to the one produced by your body that will predispose people with diabetes to gain undesirable weight?

Type 1 Diabetes and Insulin

For those with type 1 diabetes, insulin-producing cells are destroyed. This is why undiagnosed patients often lose weight. Once they begin to administer insulin via injection or infusion, it makes sense that they may gain weight. This is good as long as they gain an appropriate amount of weight to be in the optimal range.

Sometimes, excess weight gain occurs. However, just as for a person who naturally produces their own insulin, weight gain is likely a result of lifestyle factors, and specifically, of consuming too many calories. While insulin is necessary for fat storage, if excess calories are not consumed, the appropriately-matched amount of insulin should not facilitate excess fat storage.

Strikingly, a recent report describes that

“Though patients with type 1 diabetes (T1D) have traditionally been thought to have lower BMI, current research has shown otherwise. The trend of increasing obesity prevalence has increased at a faster rate in patients with T1D compared to the general population. Currently, around 50% of patients with T1D are either overweight or obese… Patients with T1D who show clinical signs of type 2 diabetes such as obesity and insulin resistance are considered to have ‘double diabetes.’”

Experts suggest several potential reasons why people may more likely to gain weight on exogenous insulin:

“Insulin-associated weight gain may result from a reduction of blood glucose to levels below the renal threshold without a compensatory reduction in calorie intake, a defensive or unconscious increase in calorie intake caused by the fear or experience of hypoglycaemia, or the ‘unphysiological’ pharmacokinetic and metabolic profiles that follow subcutaneous administration [although this is largely theoretical].”

Taking in too many calories (and the corresponding insulin), which may or may not stem from fear of low blood glucose events, or suboptimal insulin dosages that elicit hypoglycemia (and the corresponding carbohydrate corrections) may be at the heart of the issue.

Experts note several possible strategies to help mitigate undesired weight gain for patients with type 1 diabetes, including “dietary intervention, increased physical activity and exercise, adjustment of insulin therapy, adding other diabetes medications that positively impact body weight, or adding anti-obesity medications.”

Type 2 Diabetes and Insulin

For people with type 2 diabetes, weight gain upon starting insulin therapy may also be a concern. For people with type 2 diabetes, insulin resistance is a major factor. Also, the use of other medications for diabetes or associated conditions may play a role in excessive weight gain.

Interestingly, research suggests that “insulin therapy itself does not induce weight gain in patients with type 2 diabetes.” Another research study noted that “insulin-associated weight gain in type 2 diabetes is associated with increases in sedentary behavior.”

In addition, a recent publication describes that

“By the time insulin was started, a high baseline A1C and insulin dose requirements were independently associated with greater weight gain, as was lower baseline BMI. Insulin regimen per se was not a predictive factor.”

Experts also note that

“Several factors are associated with weight gain and more intensive therapy: failure to compensate for calories no longer being lost through glycosuria, intake of extra calories to treat more frequent episodes of hypoglycemia, repletion of body water due to periods of poor glucose control, and habitual overeating. Overall, increased caloric intake leads to weight gain and increased insulin resistance, which then exacerbates the progression of diabetes. Hunger is a symptom of hypoglycemia, which in many cases can lead to overeating. A patient’s fear of hypoglycemia can also lead to insufficient use of insulin or chronic overeating in order to try to prevent hypoglycemic episodes. This so-called “defensive snacking” can be a habit for many people with diabetes as they try to control or prevent hypoglycemic episodes.”

They conclude that

“Although insulin therapy carries the risk of weight gain, with careful management of diabetes-related therapy, weight gain is not inevitable. A variety of lifestyle changes and targeted therapies are currently available to achieve the lowest possible weight change while maintaining adequate glycemic control.”

So, as with type 1 diabetes, undesired weight gain with type 2 diabetes is not inevitable. However, patients must be careful not to overconsume calories and work with their healthcare provider to optimize insulin dosing so as to minimize hypoglycemia (and the fear of hypoglycemia that may promote overeating).

Tips for Achieving or Maintaining Optimal Weight on Insulin Therapy

Pay attention to diet : Consuming too many calories will likely lead to weight gain. Making sure to get appropriate amounts of protein, a necessary building block that can help you feel fuller longer, is a good idea and can help you minimize excess carbohydrate and fat consumption.

: Consuming too many calories will likely lead to weight gain. Making sure to get appropriate amounts of protein, a necessary building block that can help you feel fuller longer, is a good idea and can help you minimize excess carbohydrate and fat consumption. Make sure your insulin doses are set correctly : Using too much insulin for your needs will cause hypoglycemia and lead to excess carbohydrate (calorie) consumption which may lead to unwanted weight gain.

: Using too much insulin for your needs will cause hypoglycemia and lead to excess carbohydrate (calorie) consumption which may lead to unwanted weight gain. Treat low blood glucose with precision : Using specific amounts of glucose and not overtreating low blood glucose can go a long way to help you not consume too many calories (and have to take additional insulin from overcorrecting).

: Using specific amounts of glucose and not overtreating low blood glucose can go a long way to help you not consume too many calories (and have to take additional insulin from overcorrecting). Exercise regularly : Exercise is great for improving insulin sensitivity and may make it easier to maintain your weight.

: Exercise is great for improving insulin sensitivity and may make it easier to maintain your weight. Choose water: Sometimes, when we feel hungry, we may just be thirsty, and choosing water is an essential step to being hydrated, feeling fuller, and is a healthy beverage that will not spike your blood glucose levels. For those looking to avoid weight gain, saving your calories (and insulin) for your meals is a great idea.

Conclusions

The bottom line is that while insulin is necessary for fat storage, it is not insulin, but rather excess insulin that can promote undesired weight gain. People with diabetes must ensure that their insulin therapy is appropriately set to minimize hypoglycemia and must pay attention to their caloric consumption to prevent unwanted weight gain.

It is a good idea to talk to your healthcare provider for help with insulin dosing or related questions about diet, exercise, weight, and appropriate medication adjustments.

You can learn more by reading about the science of weight loss and consider the relevant factors for losing weight with type 1 diabetes and type 2 diabetes. Also, check out this article about how to improve your insulin sensitivity.

Read more about A1c, diabetes weight gain, exercise, insulin, Intensive management, low blood sugar (hypoglycemia), weight gain.