Dangers of Fructose

Dangers of Fructose

Fructose is your new mortal enemy

We all know that impaired glucose metabolism is diabetes in a nutshell. But we also know glucose is not the only component in sugar. So what about the other component of sugar? Does it also lead to metabolic disease? We spend a lot of time looking at the concerns an overindulgence of glucose (i.e. simple or complex carbohydrates) pose, but there is another sugar molecule out there that has a very unique pathway to destruction: fructose.


Anger at fructose

Fructose is actually arguably worse than glucose for many reasons, but one major problem is its contribution to visceral adiposity. Don’t worry, I will break down the different names of sugar and types of fat so you can follow along easily. But for now simply know there are different kinds of “sugar” and different kinds of stored fat. Some are worse than others.

If you want a quick and practical application of this topic without going too deep into the science, then here it is. Eliminate all fructose from your diet aside from fruits as infrequent desserts. That includes things like table sugar, fruit juice, soda-pop, candy, and anything containing high fructose corn syrup. Avoid it all. Taking that one simple step will accelerate you 100 miles forward on the road to health. Trust me – added fructose is no bueno.


While there are many dangers of over-consumption of fructose, this article mainly focused on its role in visceral adiposity. That is a fancy term for abdominal fat that surrounds your internal organs. Visceral fat is the really bad kind of fat. It interferes with proper metabolic processes, and leads to things like insulin resistance and heart disease.

In order to avoid visceral fat accumulation, you must avoid fructose. Plain and simple. The research studied this week hails from the United States and India. They look at the possible mechanisms for how fructose ingestion leads to visceral adiposity.[1] Feel free to take a look at the article for yourself and follow along. [Click here for the file.]

DiNicolantonio JJ, Mehta V, Onkaramurthy N, O’Keefe JH. (2017). Fructose-induced inflammation and increased cortisol: A new mechanism for how sugar induces visceral adiposity. Progress in Cardiovascular Diseases. https://doi.org/10.1016/j.pcad.2017.12.001.

Here are the most relevant points of the article I found:

  • Fructose consumption causes inflammation in subcutaneous (“normal”, under-the-skin) fat.
  • That inflammation leads to a rise in cortisol to help mediate the problem.
  • The cortisol causes an exodus of free fatty acids from the subcutaneous fat to then be deposited as fat around the organs
  • Fructose causes the medical condition, “thin on the outside, fat on the inside.”


There is a bunch of talk around different forms of dietary sugar. There is also a lot of talk around the different kind of fat formations in your body. Because it can get a little confusing, I want to take a bit of time explaining the differences between them. This is only a brief overview, but if you have a good understand of these differences, then go ahead and skip this section.

Types of sugar

There are so many names of sugars that it can be hard to keep track of. There are 3 major kinds which are the most important in the modern diet: glucose, fructose, and sucrose. Anything ending in “-ose” indicates a type of sugar or saccharide.

Glucose is the most popular topic because of its relation to diabetes. Glucose is the main product of carbohydrate consumption, and it is the major substrate used for energy in the body (if not on a ketogenic diet). Diabetes is the condition where your body does not metabolize glucose properly, usually from insulin resistance. Your pancreas releases insulin in response to high blood glucose levels. When people talk about “blood sugar”, this is what they are talking about.


Molecular structure of glucose

Fructose is a similar kind of saccharide, but it differs slightly in its structure which means that it goes through a different metabolic pathway. It does not cause the release of insulin. It also is not mainly processed by the liver like glucose is. Rather, the small intestine is responsible for its uptake and regulation.[2] It will convert into glucose through similar, but slightly different, processes to that of carbohydrate into glucose.[1][2] Fructose and glucose are very similar, but the metabolism differs.


Molecular structure of fructose

Sucrose is a combination of glucose and fructose, and this is what table sugar is made of. When you buy sugar at the store, you are buying sucrose. As you can imagine, this sucrose breaks down into their pieces: glucose and fructose. Once it breaks down, the pieces move into their respective metabolic pathways.


Molecular structure of sucrose

Types of body fat

There are two main kinds of fat storage in your body: subcutaneous fat and visceral fat. Although they are both made of triglycerides, it is the location of their deposition that differs. And it turns out that its location is a huge deal in normal body function.

Subcutaneous fat is the “normal” kind of fat. It is the fat that sits right under your skin and does not directly interfere with organ function. When you see obese people, it is this kind of fat that is most visible. You can pinch this kind of fat, and it is more “jiggly” than the other kind. Overweight people with most of their fat being subcutaneous are actually quite metabolically healthy. It may be surprising, but it’s true. They have proper tissue in place for the storage of fat. It’s like the crumple zone of a car. If you must have fat, that is where you want it to go.

Visceral fat is the very bad kind of fat storage. This is the fat that sits deep in your abdominal area, and that is why you might not even see someone with visceral fat as obese. It surrounds many vital organs including the liver, pancreas and heart. If someone has a very dense and hard looking stomach, they have this kind of fat. Although it can be visible, it is fairly common for it to remain unseen. It interferes with those organs and causes metabolic problems. It is responsible for things like insulin resistance and the metabolic syndrome.[1][3] You want to avoid accumulation of visceral fat to the best of your ability.


Different types of fat placement

You might also hear a term relating to certain fat stores as “ectopic fat.” For our purposes, just think of ectopic fat and visceral fat as the same thing. Ectopic just means abnormal placement, so it is common now-a-days to use the terms interchangeably.

Fructose’s role in visceral fat

Now that we understand that visceral fat is the bad kind of fat, we need to understand how it gets there so we can avoid it. The research I studied for this week goes over this in detail. I will only give a brief overview since the physiology and technicalities can be a bit confusing. Regardless, this basic understanding is enough to help us in our journey towards health. (Any claims I make here are from the studied article, but I also add some references here and there for your perusal.)

Fructose consumption causes inflammation in the cells that metabolize it.[4][5] That alone should be enough of a warning to stay away from it, but it gets worse. When your subcutaneous fat tissue metabolizes fructose, its inflammation triggers a cortisol response because cortisol comes as an anti-inflammatory agent.[6] When that cortisol comes through, it causes the subcutaneous adipose tissue to release fatty acids.

These fatty acids continue onward to the liver for further processing. Usually they will be placed on VLDL particles for delivery to other cells in the body for energy production. However, when there is no need for cells to use the fat for energy, or if the VLDL is all gone on delivery, then your liver will re-esterify the fatty acid back into a triglyceride for storage. (Learn more about the roles of cholesterol particles in your body.)


From fructose to being fat on the inside

It is usually not a problem because your body has the proper systems in place for dealing with the fatty acids. However, when there is chronic inflammation (from eating fructose), the cortisol over-does its role and keeps the door open too long for fatty acids to escape. If there is too much of a flux of fatty acids, then your liver deals with it by storing it. This means that you will form fat in and around your liver and other organs.

Weight gain with fructose

Not only does fructose cause inflammation and visceral fat accumulation, it also has a direct role in general weight gain. Let’s go back to glucose for just a second so we can compare fructose’s action to it. Glucose causes an insulin response, and if too much glucose is consumed, then the insulin will store that fat away in adipose tissues (mainly as subcutaneous fat).

Insulin is also closely tied to leptin, which is the hormone that dictates hunger. Leptin is what tells your brain that you are not hungry. When insulin is up, leptin also goes up. Your insulin is telling leptin that there is energy around, so it needs to tell the brain to make you feel less hungry. If there is not an insulin response, then there is also no leptin response.

This fact plays a huge role in explaining another reason why fructose is bad. Fructose is very low on the glycemic index and does not trigger an insulin response.[7] Because of this, fructose also does not trigger a lepin response.[8] If there is no leptin around, there is nothing telling your brain that you are full. You can eat a lot more food when fructose is a part of your diet. That leads to over-eating and, thus, weight gain.


Fructose causes general weight gain

Although eating a high fat diet also reduces your insulin (and leptin), it does not lead to over-eating. That is a topic for another time, but keep in mind that insulin and leptin are not the only hormones involved in appetite.

Other problems with fructose

Yes, fructose has even more problems than everything we’ve already talked about. As I said, fructose causes your body to create more visceral fat as opposed to subcutaneous fat. That visceral fat is responsible for metabolic problems like insulin resistance, and there is a clear mechanism for why this happens.[3] Additionally, many other studies that show the direct link between fructose ingestion, insulin resistance, and the metabolic syndrome.[5][8][9][10] As you can see, there is plenty of proof that more fructose means more metabolic instability.

Because heart disease is really a metabolic disease at its core, it was no surprise to find out that fructose consumption can also lead to cardiovascular disease.[7][10 Keep in mind also that the misplaced visceral fat can be on or very near the heart. It’s definitely got to interfere with its function, right? Yes, it does. The ingestion of fructose is also highly correlated with hypertension (high blood pressure).[11]


Fructose is bad for your heart

It is true that not all mechanisms are fully understood and correlation does not mean causation, but it is a good place to start. There are clear indications that fructose is a major culprit of chronic diseases. More research is needed, but there is one definite fact that we can take away from all this:


There is no added nutritional value to its consumption, so why even mess around with it? Don’t take a chance with your health, and please avoid anything that contains high concentrations of fructose: table sugar, fruit juices, soda-pop, candy, and high fructose corn syrup. The only fructose you should ever consume should be from raw fruit. But even then, treat it more like a dessert than a meal. Have it only once in a while as a way to satisfy your sweet tooth – the way nature intended it to be.


  • Fructose consumption causes inflammation in subcutaneous (“normal”, under-the-skin) fat.
  • That inflammation leads to a rise in cortisol to help mediate the problem.
  • The cortisol causes an exodus of free fatty acids from the subcutaneous fat to then be deposited as fat around the organs
  • Fructose causes the medical condition, “thin on the outside, fat on the inside.”


[1] DiNicolantonio JJ, Mehta V, Onkaramurthy N, O’Keefe JH. (2017). Fructose-induced inflammation and increased cortisol: A new mechanism for how sugar induces visceral adiposity. Progress in Cardiovascular Diseases. https://doi.org/10.1016/j.pcad.2017.12.001.

[2] Jang C, Hui S, Lu W, et al. (2018). The Small Intestine Converts Dietary Fructose into Glucose and Organic Acids. Cell Metabolism 27(2): 351-361.

[3] Snel M, Jonker JT, Schoones J, et al. (2012). Ectopic Fat and Insulin Resistance: Pathophysiology and Effect of Diet and Lifestyle Interventions. International Journal of Endocrinology. https://doi.org/10.1155/2012/983814

[4] Glushakova O, Kosugi T, Roncal C, et al. (2008). Fructose Induces the Inflammatory Molecule ICAM-1 in Endothelial Cells. Journal of the American Society of Nephrology 19(9): 1712-1720.

[5] Choi ME. (2009). The Not-so-Sweet Side of Fructose. Journal of the American Society of Nephrology 20(3): 457-459.

[6] Pioli PA, Guyre PM. (2011). Cortisol Exerts Bi-Phasic Regulation of Inflammation in Humans. Dose Response 9(3): 332-347.

[7] Segal MS, Gollub E, Johnson RJ. (2007). Is the fructose index more relevant with regards to cardiovascular disease than the glycemic index?. European Journal of Nutrition 46: 406-417

[8] Elliott SS, Keim NL, Stern JS, Teff K, Havel PJ. (2002). Fructose, weight gain, and the insulin resistance syndrome. The American Journal of Clinical Nutrition 76(5): 911-922.

[9] Stanhope KL, Schwarz JM, Keim NL, et al. (2009). Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans. The Journal of Clinical Investigation 119(5): 1322-1334.

[10] Johnson RL, Segal MS, Sautin Y, et al. (2007). Potential role of sugar (fructose) in the epidemic of hypertension, obesity and the metabolic syndrome, diabetes, kidney disease, and cardiovascular disease. The American Journal of Clinical Nutrition 86(4): 899-906.

[11] Hwang IS, Ho H, Hoffman BB, Reaven GM. (1987). Fructose-induced insulin resistance and hypertension in rats. Hypertension 10: 512-516.

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  1. […] suggest that fructose is 10 times as reactive as glucose in generating AGEs. (Check other blog post on the dangers of fructose if you are interested in learning more about its specific […]

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