Insulin Causes Weight Gain – Hormonal Obesity IV

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In our previous post, we were reviewing the link between insulin and obesity.  It appears that insulin is not merely associated with obesity but causes obesity.

Click here for Hormonal Obesity Part I, Part II, and Part III.

For decades we believed the Caloric Reduction as Primary (CRaP) hypothesis of obesity that turned out to be as useful as a half-built bridge.  Study after study showed that reducing calories did NOT lead to weight loss.  Patient after patient tried to lose weight by restricting calories with consistent failure.    But we couldn’t abandon the calorie model so what was left to do?  Blame the patient, of course!

Since patients were not losing weight, there was only 2 possibilities.  Either the advice to eat a low fat, calorie restricted diet and exercise more was wrong or the patient was not following this advice.

So the doctors and dieticians berated, ridiculed, belittled, rebuked, chided and reprimanded.    We said – Eat less, Move more – as if that would cure their problems.  After all, the food pyramid couldn’t be wrong, could it?  But the excess weight was still as persistent as a nagging tooth.

Doctors, of course, were drawn to this CRaP hypothesis as bathers to a seashore.  Obesity was now not our failure to understand it, but their lack of willpower and/or laziness (gluttony or sloth).  It was our favourite game – blame the patient.

But, of course, the problem was the CRaP hypothesis.  It was just wrong.  Increased calories did not cause obesity so reducing calories didn’t cause weight loss.  Exercise didn’t work either, as we will see in a future series.  So, what was the real aetiology of obesity?  Insulin.

Hormonal Obesity Theory

What happens when we give high doses of insulin to patients?  Insulin makes you gain weight.  The more insulin you take, the more weight you gain.  It almost doesn’t matter how much you eat or how much you try to exercise.  The weight just keeps coming on.

An interesting experiment that demonstrated this exact principle involved intensive treatment of diabetic patients.

Intensive Conventional Insulin Therapy for Type II Diabetes

Diabetes Care 16:23-31 Henry RR

The researchers took 14 diabetics and increased insulin until sugars were almost normal.  At the beginning, they were on pills only.  Over the 6 months, insulin was increased until the were taking an average of 100 units per dayInsulin 3.

Body Weight increased by 8.7 kg (19 lbs).  Yet, if we were to look at daily caloric intake, we can see that the average patient decreased by almost 300 calories/ day!  In other words, despite eating less patients were gaining weight like crazy.  That means that it was not the calories that was driving the weight gain.  It was the insulin!

Think about it this way.  Insulin is the hormonal signal to the body to increase weight – the Body Set Weight (BSW).  If insulin is increased, we increase our BSW.  In order to reach this new, higher weight, we will need to eat more or decrease total energy expenditure (TEE).  So the insulin makes us fat.  In order to get fat, we will eat more or reduce TEE.  The behavior of eating more is in response to the hormonal signal to get fat.

In this study, insulin dose was massively increased.  Under this hormonal signal, the body tries to gain weight (increase the BSW).  As weight increased, patients tried to restrict calories.  Since they weren’t eating more, their body is forced to ‘shut down’ in order to conserve energy to increase weight.  TEE is lowered.  We feel tired, cold, and hungry.  And the weight still keeps going up.  Sounds like most conventional low fat low calorie diets.  Diet, exercise, feel lousy and still can’t lose weight.

Insulin 4

There is, in fact,  a direct correlation between total dosage and weight gain.  The more insulin given, the more weight gained.  The higher the insulin levels, the more weight gained.  Insulin causes obesity.

A more recent study (N Engl J Med 2007;357:1716-30 Holman RR) showed this exact same effect.

Addition of Biphasic, Prandial, or Basal Insulin to Oral Therapy in Type 2 Diabetes

In this study, 708 diabetics on oral medications got insulin added to their treatment.  What happened to weight?  It went up.  That is really no surprise – every clinician already knows that insulin makes you gain weight.Insulin 5


Those who got the highest doses gained the most weight.  Those who got the least, gained the least weight.

Insulin can not only cause generalized obesity, but it can also cause localized fat growth.  Those who regularly inject insulin may occasionally experience lipohypertrophy.  This just to reinforce the notion that insulin is the signal to gain fat.

There are those who might argue that it is simply the treatment of diabetes that causes weight gain.  As we reduce blood sugars, that sugar is taken out of the blood and into the body as fat.

If this were true, then any treatment of diabetes should cause equal weight gain.

We can compare treatment of type 2 diabetes with different agents.  Luckily for us, these studies have already been done.  This was the large UKPDS  (UK Prospective Diabetes Study).

Let me explain here.  There are several pills for diabetes (oral hypoglycemics).

Sulphonylureas (SU) are a class of medication that will stimulate the pancreas to produce more insulin.  If insulin causes obesity, as the hormonal obesity theory holds, then this class of drugs should indeed increase weight.

Metformin is another class of medication.  This is an entirely different kettle of fish.  It is considered to be an insulin sensitizer.  That is, it helps the insulin in the body work more efficiently.  It does not raise serum insulin levels.UKPDS 1

This is great.  Now we can compare the different effects of the 3 types of drugs – insulin, SU, and metformin.  They all have the effect of reducing blood sugars, but the effect on insulin levels in the body are completely different.  Insulin will raise blood levels the most, SU will raise levels but not as much as insulin, and metformin not at all.

What are the effects on weight?

As we expected, the insulin group increased weight by the most.

The Chlorpropamide and gliburide (sulphonyureas) increased weight as well, but not as much as insulin.

The metformin group was weight neutral.  This group did not gain any more weight than those on diet alone.januvia

So insulin, and gliburide (which raises insulin levels) both increase weight.  Metformin, which treats the blood sugar but does NOT raise insulin levels does not raise weight.

Since the publication of the UKPDS there has been the introduction of a new class of drugs to treat diabetes.  These are the DPP4 class of medications.

The mechanism of action of these drugs is to increase insulin levels in response to a meal.  It does not cause a persistent elevation of insulin levels.  As we would expect, the DPP4′s are weight neutral.

In this study, glipizide (a sulphonylurea that raises insulin levels), causes weight gain.  Januvia, which does not persistently raise insulin levels does not.  This is despite the fact that sugars are treated to the same level.

The results are very consistent.  Raising insulin levels causes weight gain.  Lowering insulin levels causes weight loss.  Increasingly, we are recognizing the importance of these hormonal factors on obesity.  Just recently, another study entitled “Insulin resistance and inflammation predict kinetic body weight changes” showed that the strongest predictor of weight regain is insulin resistance.  Not willpower.  Not caloric intake.  Not peer support.  Insulin.  Insulin.  Insulin.  It is all about the insulin.

Under the influence of insulin, our body receives instructions to “gain fat”.  In response, we eat more and/ or decrease energy expenditure.  It is not a voluntary act.  Remember this:Imbalance

The question is NOT how to balance calories, the question is how to balance our hormones.  In most cases, the crucial question is not how to reduce calories but how to reduce insulin.

Continue to Hormonal Obesity part V here

Begin here with Calories I

Click here to watch the entire lecture – The Aetiology of Obesity 1/6 – A New Hope

2017-09-02T11:54:31+00:00 40 Comments

About the Author:

Dr. Fung is a Toronto based kidney specialist, having graduated from the University of Toronto and finishing his medical specialty at the University of California, Los Angeles in 2001. He is the author of the bestsellers ‘The Obesity Code’ and ‘The Complete Guide to Fasting’. He has pioneered the use of therapeutic fasting for weight loss and type 2 diabetes reversal in his IDM clinic.

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40 Comments on "Insulin Causes Weight Gain – Hormonal Obesity IV"

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Abe Ramat

Yes, but HOW does insulin make you fat? What are the physiological mechanisms, and how do they interface with satiety, hunger, adiposity, lipolysis, and TEE? HOW do they shift the BSW? How does the insulin prevent the typical neutralizing relationship between calories in and calories out? What are the other hormones involved?

I am devastated that since they put me on insulin, I have gained over 30 lbs in 6 months. I was gaining at a rate of 10 lbs per week and even gained 3 lbs since my last doctor visit 3 days ago. I don’t know what to do. I exercise 1/2 hour a day and do not eat junk. I am beside myself as this has caused my self esteem to go down the tubes. I have struggled with my weight for 40 yrs and what the hell am I going to do now ? I can’t afford more… Read more »

This is happening to me too…What do we do !! I have gained 40lbs too… I don’t want to gain any more !


Dr. Jason fung is your answer


I have been over weight since I was 8 years old. I weighed 150 and when I was 10 210 pounds now I’m a diabetic and can not loose a pound I eat very healthy no junk and drink gallion of water every day. I’ve tried everything no sugar no milk no eggs or animal by product. I do not know what to do.


Try intermittent fasting combined with local carb low calorie diet. This is almost a guaranteed prescription to lose weight and improve insulin sensitivity. If you are on insulin or taking other drugs, please consult your doctor before starting.


The only thing that would make any sense to you is getting off the insulin. You can achieve this by eating low carb, high fat. As little as 50 grams net carbs per day and most of it from veg. Lots of saturated fats and medium servings of protein. Eat like that and you will become healthier and slimmer. Always consult your physician when doing this ofcourse.


The only thing that would make any sense to you is getting off the insulin. You can achieve this by eating low carb, high fat. As little as 50 grams net carbs per day and most of it from veg. Lots of saturated fats and medium servings of protein. Eat like that and you will become healthier and slimmer.

OMG! This article could have been written about my life! I was on Metformin and Gliburide for my diabetes for years, but unfortunately they weren’t effective for me. I was able to lose weight and I did lose 135 lbs. But my sugar levels kept going up. Finally, a doctor put me on insulin and sure enough my sugars stabilized to an almost normal level. I was excited, I was thrilled! But my weight started to creep back up. I regained about 80 of the pounds I had lost. I was devastated. No matter what I did, I couldn’t lose… Read more »

[…] Insulin resistance will make your thyroid worse by inhibiting T4 to T3 conversion. Insulin resistance also makes your cells more resistant to thyroid hormone floating around in the blood. This is why many people may have “normal” levels of thyroid hormone in the blood but low levels of thyroid hormone in the cells (this phenomenon is known as thyroid resistance). […]

Russell Eaton

I cannot praise Dr Jason Fung highly enough for his outstanding analysis of the true causes of obesity. He has hit the nail. Obesity is a hormonal issue, not a calorie issue. As I explain in my book, when we mess with our hormones (for example, by consuming processed carbs) we inhibit lipolysis, the body’s own weight loss weapon.
Russell Eaton, author, The Lipo Diet,


Insulin do not cause weight gain, damaged insulin receptors is the cause. The cells can not work as evolved and due to high glucose levels the cells can’t operate as desired due to lack of leptin signaling.


Any source or study to back this theory?


This is so true sadly I’m not a doctor and I am reading this research and its true. I burn 3000+ calories a day but am gaining weight. I eat below the my daily intake and I eat healthy. The military doctors don’t understand… I am phisicaly active and still gaining.

Actually you are incorrect. You are stating the average coincidence but that is not the causality. You need to look at the extremes to find the true answer. Type 1 diabetics; produce no insulin + have high blood sugar = extreme uncontrollable weight – LOSS Insulinoma ; a tumor produces lots of insulin + very low blood sugar = extreme uncontrollable weight GAIN Both of the extremes occur with no regard to dietary intake. (and there are many other conditions that can causes one to have a similar effect, but possibly not to the extreme). Just because there are some… Read more »

How can I get started? I was diagnosed with type 2 diabetes in 2008 & after trying every oral medication, my a-1c just gradually got worse. May 2014 my doctor started Lantus every night, very shortly thereafter Humalog was added at meal time. Since then my doctor switched me to Levemir 40 units twice daily & Humalog 20-30 units at every meal. I would like to end this cycle & would like to know how to change my life. thank you.


Get Dr. Bernstein’s Diabetes Solution book Eat Low carb, high fat, moderate protein diet. It WILL end the cycle and reduce your medication.

Bonita Green
Wow this article just verified my suspicions! Diagnosed in 1999..I’ve run the gamut of metformin, glidizide, insulin. In 2014 I weighed 257 lbs and just felt awful. Diet and exercise did not help. In January 2015 I stopped taking everything! The weight poured off 97 lbs later! February 2016 I went in for a check up and my a1c was 15 and I felt awful. I weighed 143 lbs and had a self confidence I hadn’t had for over 20 years! I went back on insulin..toujou ..and guess now I weigh 183 lbs. I’m so mad at the medical field..for… Read more »

[…] Click here for Hormonal Obesity Part I, Part II, Part III and part IV. […]

Mikael is correct. There is a whole lot more than this going on. The only reason people put on so much weight is because the sugar is finally out of their blood stream (and they are having normal BS readings). what should have been shared is what the A1C results were of these people in the test groups (both before and after the study). If your a1C is very high (over 10), your body will quickly lose weight, but the damage occuring on the inside is overwhelming! Then you get on insulin, your a1c drops to a 7, but you’ve… Read more »

Saturated fats are okay. I think Anita meant to go ahead and eat sat fats, because it’s hard to eat LCHF and avoid sat fats.


Excercise and avoid saturated fats… Hmm I wonder if anyone tried that before 🙂

After I read Dr. Bernstein’s book I decided to become a patient. The book has been through many editions and is quite precise and thorough. The one area that he does not cover, and Dr. Fung does, is fasting. Dr. Fung has done us all a great service by showing how fasting regimens can be integrated into a Bernstein-like regimen. I am not aware of any other fasting advocate who has done so much to inform us of how to combine fasting with low-carb. Before I had heard of Dr. Fung, I was experimenting with fasting, but all the material… Read more »

I am a type 1 and I exercise and count calories. I still keep gaining weight! It is offensive to those who didn’t ask for this disease when people say things such as those have in the above conversation. I’m at my whits end with this. I agree with the article because I live it everyday. So with all that being said please find a cure. I’ve done the low carb high protein diet and in one month lost .5 lbs. Anyone have a better solution?!


Mary, Try low carb high fat moderate protein. or if you click JOIN above you can actually get hooked up with a dietician to work with your doc to help you with it. Since your type 1 I believe the goal is to get your sugars down low enough that you can take minimum amount of insulin.

lydia Broeker

I was started on glipizide, added to the already metformin. the glipizipe dropped by Blood sugar significantly if I ate low carbs, which in turn sent me hypo (low) glycemic-feeling very bad. so what happens next, I eat a gang of sugar to up the blood sugar, which shots from 50’s to high 200’s. well no wonder the weight gain and insulin resistance is going on. The last two days I have not taken the glipizide, eating almost sugar free, losing weight, and blood sugars steady at 130’s (good for me). thank god for this article.


[…] Jason Fung’s blog post Insulin Causes Weight Gain – Hormonal Obesity IV gives far more insight into the causes of obesity and the solutions for it. For those who want to […]


[…] Insulin Resistance is associated with weight gain and can lead to Diabetes.  Don’t screw your Insulin sensitivity up by shoveling away the simple carbs.  Take it easy, and try to eat low glycemic carbs. […]


Unfortunately, there are many causes of obesity including genetics, hormones (not just insulin), gut micro biome…. However, these account for a very small percentage of the cause of the epidemic in obesity. Excess calories and decreased energy expenditure still account for majority of the cause obesity. Weight loss also requires not just caloric restriction, but also improving the kinds of foods consumed. It seems that this article is completely one-sided and biased. I think readers should be cautious not to take this information to heart.

Randy Throckmorton
I’ve been a type II diabetic for 20 years. It isn’t until the last couple of years that I have had uncontrollable weight issues. I gained 40 pounds last year while exercising the same and eating the same. My response was to increase my exercising and cutting back on my low carb low sugar diet. I now walk or walk/run 10 miles a day and still gained 10 more pounds at my most recent doctor appointment. I burn 4,000 plus calories most days with my exercising but weight won’t go away. It seems like a vicious cycle. The more insulin… Read more »

[…] if consumed in the morning. It is increasingly believed that weight gain and obesity are a direct result of chronically elevated insulin levels. Therefore, a key weight management strategy should be to […]


[…] Insulin Causes Weight Gain […]


Abe, please read the comments above befire asking again. Thank you.

I am very interested in your articles! I had a question though: If plasma insulin is related to weight gain, but insulin that is utilized by the body is not, why do type 1 diabetics experience significant weight gain? They tend to dose insulin based on the carbs at a meal, they do not chronically have higher levels of insulin in their systems, and their cells aren’t resistant to it (normally) so the insulin should be used. It would make sense to me that if metformin and DPP4’s are weight neutral, a type 1 diabetic dosing insulin appropriately would also… Read more »

Susan- you need to go on a low carb high fat diet. Google lchf 🙂 you will lose weight, feel better and prob need less medication:)


Sorry folks, it is what people consume, if you didn’t have all the carbs running around the body insulin couldn’t store it away as fat. If you do low effort, steady aerobic exercise your body will convert stored fat for energy. It is that simple. This guy is just saying look we know the mechanism!!!


If it’s as simple as you say. Then you are a genius and have solved the worlds diabetes problems. You have obviously never lived with this condition and should keep off forums as your advice is complete rubbish

Deana Judah

I’m not diabetic…I do have high Insulin levels. Ive tried every diet out there…cant lose frustrated!!!
I’m on Metformin to try and bring levels down to lose weight now for 3 months…nothing! Still high!
D ont know what to do! I’m on a no added sugar, low carb diet. I’m taking CMT oil, I take Probiotics and just started taking Curcumin for inflammation…help!