Is insulin causing weight gain?

I was diagnosed with Type 1 in 2009 and have been on multiple pumps with MDI breaks in between. I’ve always been the same size. Even after my pregnancy. My close fit the same, I was the same weight. My diet has remained the same the entirety of my adult life. When I turned 30 last August I noticed my weight start to creep up and within three months I gained 25 pounds! I’ve never had this happen. I’ve never had to do anything to lose or maintain my weight. My endo said that injectable insulin is the culprit but I’ve been injecting/pumping insulin for the last 14 years. That doesn’t make sense to me that nine months ago my body just decided, hey, you know what? She’s injecting her insulin, let’s store some excess glucose as fat!

What gives? Has anyone experienced anything similar? My endo suggested Affreza and adding ozempic which I’m cool with because I’d like to decrease my insulin requirements (which has also increased) and I’ve been curious about Affreza since it came out so I’m excited to try it.

Nope, not because of insulin: Does Insulin Cause Weight Gain? It really is about what you eat and how much activity you get.

Maybe your activity level has decreased? That is a pretty significant weight gain in a short period of time. Maybe something else is causing it, not diabetes-related?

I take Ozempic and I love it! (Tried Trulicity and Victoza in the past too.) They all have kept food cravings at bay. I highly recommend it!


And I disagree with Allison. You state that you now take more insulin. That also means that your intake of carbs has increased. Between the two, you could have gained weight. Also, as one gets older, one needs to exercise more. Try cutting down on carbs and exercising more. Your TDD of insulin should come down as well AND you should stop gaining weight and, eventually lose some. Try it.


The question was does insulin cause weight gain? The answer is NO, food causes weight gain. She’s been on insulin for a long time. There has to be something other than insulin causing that big of a gain in that short period of time. It may be from eating more carbs… again, that’s food causing it; not insulin.


What we both say is true. Insulin is a fat storing hormone which also helps process the food we eat. If there is more than our bodies need, then the insulin will store the energy in fat. I stand by what I said above.

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That’s only true when there’s an excess of glucose not being used or the liver is saturated. It goes back to @Allison1 too much food covered by too much insulin. Reduce the food and reduce the bolus


Isn’t that what I said above?

I have seen at least one study that showed well-controlled T1D’s gained more weight, and my cursory search looking at legitimate sources would say that it can and does, but with some caveats, depending on how often one experiences hypoglycemia, or if one has disordered eating practices. Even then, it does pay to follow careful dietary practices to avoid or reduce weight gain.

Does Type 1 diabetes affect your weight? If yes, how?

A broad DCCT (Diabetes Control and Complications Trial) study conducted in the United States, with a population of people living with Type 1 diabetes, established that intensive insulin-based treatments (pump or at least three insulin injections per day, with a view to returning blood sugar levels to a normal range) which allowed for better control over blood sugar levels, had also caused an average weight gain of 4.8 kg compared with traditional treatments (a maximum of two insulin injections per day and broader blood sugar targets). However, this excess weight wasn’t uniform across the population. It was time-limited (mainly to the first year) and was particularly linked with the improvement of the initial glycemic control. The study concluded that the higher the blood sugar levels at the start of the intensive treatment, the more weight gained by the subjects.

Type 1 diabetes: what factors may cause excess weight and/or weight gain? | dbl-diabetes

Studies do agree with the idea of insulin use and weight gain, noting that obesity is increasing in T1D’s, particularly if they have a family history of T2D, but again, they also describe how it might be managed:

Weight Management in Patients with Type 1 Diabetes and Obesity - PMC (

Insulin-associated weight gain in diabetes–causes, effects and coping strategies - PubMed (

Weight Management in Patients with Type 1 Diabetes and Obesity - PMC (

Weight gain and insulin treatment - PubMed (


I think that there exists a larger truth here that does not disprove anything anyone has already asserted. The important point is that human beings are hormone-driven systems. Hormones ebb and flow and as a T1D we must keep track of the ever-changing hormone levels – both in the short term and longer term.

Males and females are subject to different hormone challenges. Weight gain after normal weight for many years, however, is present in many of both genders.

The total daily dose of insulin is a useful thing to monitor as more insulin usually equates to more body weight.

The answer to the OP’s question is only answered by personal experimentation that she may choose to perform. I suspect that she will find a variety of factors may be involved.

Thirty is young but her body may have decided to make different choices regarding metabolic and energy-split decisions.

The bright spot is that recently gained weight is much more easily shed than weight that has been stored long term.

I suggest (at the risk of a man’s suggestion about a woman’s weight!) that you do some personal experimentation. You may find that your style of eating may benefit from some changes.

Good luck and please forgive this male from weighing in on a precarious topic!


I’m not on a pump, but this might be interesting for those who are:

Excess weight gain was associated with lower bolus to basal insulin ratios independent of glycemic control and activity level. Evaluation of bolus and basal insulin doses during insulin therapy is warranted in order to avoid excess weight gain.

Excess weight gain during insulin pump therapy is associated with higher basal insulin doses - PMC (


“Fine tuning” of diabetes management with intensive insulin therapy was accomplished without inducing weight gain or worsening hypoglycemia. This was achieved by readjusting the ratio of basal to meal-associated insulin without increasing the total daily insulin dose.

Uncoupling Intensive Insulin Therapy from Weight Gain and Hypoglycemia in Type 1 Diabetes - PMC (


I am a woman who has had type 1 for 63 yrs. I have gone through many hormonal changes, since I was 8 when diagnosed and am now 71. I have also had a child. I am only one person, but I have never believed that insulin causes weight gain. The only time I gain weight is when I don’t watch what I eat. My mom was heavy and my son is overweight by quite a bit, but I am thin. If I don’t watch what I eat I gain weight. If I gain an extra 5 lbs, I eat less and exercise more until I am back to my normal weight. Both watching what I eat and exercising daily requires a lot of discipline.

If I don’t exercise and don’t watch what I eat, I gain weight. Insulin doesn’t affect what I weigh and never has.


The studies you cite provide persuasive evidence of different basal/bolus nature of insulin therapy. I agree withe general concept but I’ve seen a bias in the studies that favor the 50%/50% basal bolus split.

I eat a low carb diet and often split my basal and bolus to about 33% basal and 67% bolus. I suppose these studies consider me an outlier but I think
we’re worth a mention.

I wonder what @Marilyn6 and her high carb low fat diet experience is with regard to a healthy basal/bolus split.

Only if one is eating too much for maintenance and activities. In type 2 diabetes (I am one) the cellular insulin resistance causes a malnourished cells with high blood glucose and insulin levels. Because of the surplus of both glucose and insulin that surplus is stored as fat.

I take 10 or 11 units of Tresiba and 9 to 11 units of Novolog, so about a 50/50 split. I eat around 250 healthy plant carbs daily. I eat very little fat. I may be old fashioned, but I have always used close to a 50/50 split.

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Insulin causes weight gain because you stop peeing out your calories. Of course you are really gaining weight because you are eating too much, but it might feel like it’s insulins fault because you can get used to over eating before insulin

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You might get your thyroid checked. Type 1’s also commonly have a autoimmune thyroid issue. And if your body is going after your thyroid, that can cause weight gain easily and fast. Even if your thyroid tests in the “normal” ranges, it might not be the optimum range. But also commonly through life our metabolism changes. Hormones ebb and flow and it’s around 30 that DHEA starts to subside and it’s the “mother” hormone that is thought to control a lot of other hormone signals in the body.

But if you’ve gained weight, which can also make you a little more insulin resistant and then you’ve upped your insulin, it still comes down to excess calories for what you need at this point in time and will cause you to gain weight. I watch my insulin intake because if I use over 50 units a day for a couple of days I will gain weight, but that’s because it’s a sign I was eating more. Under a certain amount of insulin means I am more likely to (slowly) lose weight,but it means I am eating less.


I held off from suggesting thyroid, not sure why. BTW we type 2s are susceptible to thyroid problems as well.


Good point Marie. I am hypothyroid and it took years to get it to a reasonable level. I had to crash my TSH level which isn’t good, but the only way I could get decent FT3 and FT4 levels.


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I fell off and never responded to this thread but I’ve been reading through all the comments and it’s starting to all make sense. I increased my long acting over time to cover some of my meals so I wouldn’t have to stop and inject. Clearly that has backfired.