Your question, answered: Does insulin cause weight gain?

Relying on insulin therapy to keep your blood sugar levels in check? You might be concerned that it's causing you to gain weight.

In short, there is a connection between insulin and weight gain — namely that taking insulin can contribute to putting on weight.

Below, we’re diving deeper into the link between the two, what kind of weight gain insulin can cause, and how you can try and manage your weight while relying on insulin injections.

What's the link between insulin and weight gain?

Insulin is a hormone produced by the pancreas. It plays a number of important roles, including turning food into energy and regulating your blood sugar levels.

The way insulin works is that it effectively helps transport glucose from your bloodstream to your cells, thus providing them with energy.

People with diabetes, however, have issues with insulin. In type 1 diabetes, the immune system attacks and destroys the cells that produce insulin, and the body becomes unable to make much of it — or none at all.

In type 2 diabetes, the cells become less sensitive to insulin and don’t respond effectively to it — this is known as insulin resistance. The pancreas then overcompensates by making more insulin, but over time, this can eventually lead to high blood sugar levels as the pancreas struggles to keep up.

As a result, people with diabetes typically have to rely on insulin therapy, which involves injecting insulin to mimic the natural secretion of insulin in the body. Those with type 1 need insulin therapy, while those with type 2 often use it when lifestyle changes and other medications are no longer effective.

The issue is that there’s a fairly strong correlation between insulin therapy and weight gain.

In fact, in the first year of commencing insulin therapy, weight gain can be anywhere from 3-9kg (6.6-19.8 pounds) according to one study, with a mean weight gain of 4kg (8.8 pounds) according to another [1][2]. There are several reasons for this. 

The point of insulin therapy is that it helps move glucose from your blood into your cells to make your body more efficient with energy use, thus lowering your blood sugar levels.

Once the glucose is in the cells, it’s used for energy. But if it’s not required straight away, your body stores it as fat. After some time, as your body gets better and better at harnessing energy from food, it may retain more of that unused energy as fat.

Many people also gain any weight they lose from having high blood sugar once they start insulin therapy.

Plus, taking insulin can lead to a behaviour known as “defensive snacking” [2]. This is where people with diabetes might eat more out of fear of hypoglycemia (low blood sugar), potentially leading to weight gain.

They might also get a false sense of freedom to eat what they want once insulin therapy has kicked off.

There’s also some evidence indicating that insulin can affect the parts of the brain that control hunger, possibly leading to overeating and consequent weight gain [3].

The better news is that weight gain is most pronounced during the first few months of starting insulin therapy, then starts to plateau. It’s also more commonly seen in those who take rapid-acting insulin rather than only relying on basal insulin [2].

Does insulin cause belly fat?

Belly fat can be particularly problematic for those with diabetes because it can make the condition harder to manage and lead to other health problems, like heart disease, stroke, fatty liver, and some cancers [4].

While insulin is a known cause of weight gain, it doesn’t necessarily make you put on weight around around midsection. 

Instead, where excess body fat is distributed largely comes down to other factors, like genetics, age, stress, hormonal imbalances, and even overconsuming certain foods and drinks, such as sugar, trans fats, and alcohol.

How to prevent weight gain while taking insulin

It might not be possible to totally avoid weight gain after starting insulin therapy, but there are several things you can do to try and minimise it. Here are 8 of them.

1. Move your body regularly

Exercise is vital for your overall health, but especially if you’re managing diabetes and trying to keep your weight in check.

Moving your body burns calories, which can help use up any excess energy that isn’t used by your cells. It also has additional benefits for those with diabetes, including its ability to help control blood glucose levels and support your body in using insulin more effectively [6].

Aim for a minimum of 150 minutes of moderate-intensity physical activity each week, such as walking, cycling, dancing or swimming, and see if you can integrate a couple of resistance training sessions, too. 

2. Avoid skipping meals

You might be tempted to curb your calorie intake by skipping a meal, but doing so can create even more problems.

Skipping meals can cause low blood sugar levels and extreme hunger, potentially making you want to eat even more or opt for unhealthy foods.

Instead, eat regular balanced meals throughout the day to keep your blood sugar and energy levels in check and reduce the temptation to reach for unhealthy options. If you have to go out, take some healthy snacks with you to avoid impulse purchases.

3. Eat mindfully and watch your portions

Portion control is essential when you’re trying to maintain or lose weight, but especially so if you’re on insulin therapy. Even if you’re eating something healthy, overeating can lead to consuming too many calories and possibly putting on weight.

There are several ways to be mindful of portion sizes. For example:

• You could use a smaller plate so you’re not tempted to fill a larger one with too much food
• You could weigh or measure your food to ensure you’re sticking to reasonable portions
• You could also keep a food diary to keep track of any areas where you might be overeating

Practising mindful eating may also be helpful. In this state, you pay close attention to your hunger and fullness cues, try to avoid eating out of boredom or when you’re feeling down, and only eat until you’re satisfied.

4. Choose nutrient-dense foods

A nutritious diet is one of the cornerstones of weight management and weight loss. Rather than eating processed, high-fat, high-salt and sugary foods, stick to nutrient-dense ones like veg, fruit, whole grains, lean proteins, and healthy fats.

The former can cause blood sugar spikes, while the latter can keep your blood sugar levels stable.

Eating foods that are rich in fibre is particularly important, as these can help you feel fuller for longer — potentially reducing the desire to overeat.

Lean proteins are also great, as they can help build muscle and support weight loss.

5. Stay hydrated

It’s really important to stay hydrated, as diabetes comes with a higher risk of dehydration [7].

Adequate water intake is also beneficial for weight loss because it can help you feel full and potentially reduce the urge to overeat. Thirst can be mistaken for hunger, too, so when you think you need a snack, you might actually just need a glass of water. 

Aim for around 1.6 litres, or eight 200ml glasses, per day [8].

6. Take your insulin as directed

Even though there’s a known link between insulin and weight gain, it’s crucial that you continue taking your insulin as directed.

Skipping or lowering your insulin doses can be really problematic, with a serious risk of complications like diabetic ketoacidosis (which can be fatal), kidney and nerve damage, and vision loss [9].

7. Speak with your doctor

If you’re struggling with losing weight, don’t hesitate to reach out to your doctor.

They can help you tailor your insulin regimen or lifestyle to minimise weight gain, possibly suggest alternative medications, or give you a referral to a nutritionist or health coach who can help you manage.

They can also ensure that your diabetes is properly managed while you’re making any changes to your diet, exercise routine or lifestyle.

8. Try a weight loss programme

Need help getting to a healthy weight? A holistic weight loss programme like Juniper’s Weight Reset could be just the thing you’re looking for.

The programme combines the expertise of several health experts, including dietitians, health coaches and clinicians, who can guide you through the necessary diet, exercise, and lifestyle changes to keep your weight in check — all while managing your diabetes.

You also get access to breakthrough GLP-1 weight loss treatments (Wegovy or Mounjaro), an online course, weight tracking, digital scales and a welcoming community of other Juniper members on a similar journey.

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