Why Insulin Causes Weight Gain – and How to Avoid It

The conversation surrounding insulin and weight gain is anxiety-provoking for many people living with diabetes. For many, the prospect of starting insulin or increasing the amount of insulin they are taking comes with a fear of weight gain. You might have heard that insulin is a “fat-storage hormone” or that once you start taking it, you will struggle with weight gain.

It’s understandable why this concern exists. We live in a society that is obsessed with the number on the scale, and for someone already dealing with diabetes, the idea of excess weight gain can feel frustrating and overwhelming.

While insulin can affect how your body stores energy, weight gain is not an inevitable side effect of taking insulin. Let’s dive into the connection between weight and insulin and what you can do to help prevent weight gain if insulin becomes a necessary part of your journey with diabetes.

The biological role of insulin

In a body without diabetes, insulin acts as the key that unlocks cells, allowing glucose from the food you eat to enter the cells and be used for energy.

When you have diabetes, that process no longer works properly. Either your body stops making insulin, doesn’t make enough insulin or the cells have become resistant to the insulin. As a result, glucose stays in your bloodstream rather than being used to fuel your muscles and organs.

This is why people with untreated or poorly managed diabetes often experience unexplained weight loss. Their bodies cannot access the fuel they need because the glucose is unable to get into the cells, so they begin burning fat and muscle to survive.

Why is insulin associated with weight gain?

When you start taking insulin or improve your blood sugar management, your body finally begins to process nutrients correctly again. This is actually a sign of healing, but it does mean that the body will stop burning fat and muscle as fuel, sometimes leading to an increase on the scale.

In addition, when blood sugar levels are high over a period of time, the kidneys work overtime to flush out the excess sugar through the urine. This process actually removes calories from the body. Once your blood sugars stabilize with the addition of insulin, you stop losing calories through the urine. If you continue to eat the same amount you were eating when your blood sugars were higher, you may see an increase on the scale because those calories are no longer being excreted through your urine. This isn’t the insulin making you gain weight, it’s the insulin allowing your body to function the way it is supposed to.

Insulin is an anabolic hormone, which means its primary job is to build and store. It helps your body store excess glucose in the liver and in the muscles as glycogen, and it signals the body to store extra energy as fat.

Overtreating lows

One of the most common reasons people experience weight gain on insulin is a cycle often referred to as “feeding the insulin” or overtreating low blood sugars.

When your blood sugar drops too low, symptoms include feeling hungry, shaky and lightheaded. A low blood sugar often causes you to consume far more than you actually need to correct the low because your brain is in survival mode, making you want to eat until you start to feel better.

If the amount of insulin you are taking is too high for your current needs, you may find yourself constantly eating to keep up with those drops. These extra calories can add up and cause weight gain over time.

Strategies for managing weight while on insulin

If you are concerned about gaining weight while taking insulin, taking less insulin than you need will not be helpful in the long run. This can lead to chronically elevated blood sugars which can increase the likelihood of developing diabetic ketoacidosis (DKA) or other long-term diabetes complications.

Focusing on optimizing your lifestyle and nutrition to better align with your insulin needs is a much safer and healthier option. Keep the following strategies in mind:

Focus on high fiber, nutrient dense foods

One of the best ways to feel satisfied is to focus on volume. Non-starchy vegetables like leafy greens, mushrooms, broccoli, cauliflower, peppers, green beans, asparagus and cucumbers are great options. They are packed with fiber, which slows digestion and helps prevent blood sugar spikes that require larger insulin doses.

By filling half your plate with non-starchy vegetables, you get to eat a satisfying amount of food while keeping your calorie and insulin needs in check.

Prioritize protein and healthy fats

Protein and healthy fats have a minimal impact on the blood sugar and require very little insulin. They also trigger the release of satiety hormones that signal to your brain that you are full.

When you pair a carbohydrate with a protein or healthy fat (like an apple with almond butter or brown rice with grilled chicken), you slow down the absorption of the carbohydrates. This leads to smoother blood sugar levels and prevents the roller coaster of highs and lows that can lead to overeating and weight gain.

Insulin timing matters

If you take rapid-acting insulin with meals, timing is everything. Ideal timing of insulin leads to better blood sugar stability. Pre-bolusing, or taking your insulin 15 to 20 minutes before you eat (depending on your doctor’s advice), allows the medication to begin working when the carbohydrates from your meal enter your bloodstream. When the timing is off, you might see a large blood sugar spike after the meal, followed by a drop later on, which may require an extra snack.

The importance of movement

Physical activity is one of the most powerful ways to reduce your insulin requirements. When you move your body, your muscles become more sensitive to insulin, meaning you need less insulin to achieve the same blood sugar result.

You don’t need to spend hours in the gym to see a benefit. Even a quick 15-minute walk after a meal can significantly lower your post-meal blood sugar.

Manage stress

Managing a chronic disease like diabetes can be incredibly stressful, and stress triggers the release of cortisol. Cortisol is a hormone that tells your body to hold onto fat, especially in the abdominal area, and it can also increase insulin resistance.

If you find yourself struggling, it is important to seek support. Stress management techniques like meditation, yoga, deep breathing or even a consistent sleep schedule can have a positive impact on your blood sugar and your weight.

Communication with your healthcare team

If you feel like you are doing all the right things and are still seeing an upward trend on the scale, consider having a conversation with your physician or a registered dietitian.

There are several things they might consider. Sometimes a different type of insulin or an adjustment to your insulin regimen can make a difference. For some people, medications like metformin or GLP-1 receptor agonists can be used alongside insulin to help manage insulin resistance and weight gain. They can also rule out other conditions such as thyroid disorders or hormone imbalances that can impact your weight.

In summary

For those living with diabetes, insulin is an important tool, not a punishment or a threat. It provides the energy your body needs to live, breathe and thrive. While the transition to insulin can be a learning curve, you have the power to influence how your body responds to it.