I recently saw a fantastic lecture titled, “Sugar: The Bitter Truth” given by Dr. Robert Lustig professor of pediatrics at UCSF. I will try to summarize the basic points here but, if you have the time, I highly recommend watching it. There is an epidemic of obesity in our country not only in adults but in children as well.  Dr. Lustig is seeing an epidemic of obesity in children as young as 6 months. His research (and that of his colleagues) has led to the conclusion that the main culprit leading to obesity is the sugar fructose. In his lecture he breaks down the biochemistry of how fructose is metab olized in our body and comes to the conclusion that fructose is  highly toxic —as toxic as alcohol.

How did we as a nation come to increase our fructose consumption so dramatically? In 1980 Dr. Ancel Keys wrote The Seven Countries Study, which was the first multivariate linear regression study (a studythat examines how different variables have an effect on an outcome) on coronary heart disease and fat.  In summary,Dr. Keys concluded that countries that ate more fat had more heart disease. However, there are numerous problems with the misleading study, including the fact that he excluded countries that didn’t fit into his hypothesis.  But more significantly, he stated: “The fact that the incidence rate of coronary heart disease was significantly correlated with the average percentage of calories from sucrose in the diet is explained by the intercorrelation of sucrose with saturated fat.” e.g., doughnuts.  He recommended that everyone reduce their intake of fat.

He didn’t take into consideration that wherever there was fat, there was sugar.  The problem with his study is that in order to conduct a multivariate linear regression study properly, you have to hold fat constant showing that sucrose doesn’t work and you have to hold sucrose constant and show that fat still works, which he did not do.  He was looking at the sugar and didn’t know it.  Unfortunately, 30 years of nutrition information has been based on this study, which turned out to be incorrectly interpreted. In 1982 the recommendation was made (based on this study) to reduce our consumption of fat from 40 percent to 30 percent. When we as a nation reduced our fat intake, we increased our intake of carbohydrates—often in the form of added sugar. A low-fat diet by definition is a high-carbohydrate diet.

What happens to our food supply when you take the fat out? In general food has less flavor and, to make up for this lack, companies had to add sugar to low-fat products to make them palatable. Thus people were inadvertently consuming more and more sugar. In contrast to modern man, a Paleolithic man consumed only about 15 grams of fructose a day in the form of whole fruit. Up to the time of World War II, sugar consumption was around 16 to 24 grams per day. This gradually increased. In 1978, when high-fructose corn syrup was introduced, consumption was up to 37 grams per day and by 1994 it was up to 54.7 grams per day.  Corn syrup is commonly found in an increasing number of common processed foods.

Adolescents today consume about 73 grams of fructose per day, or around 12 percent of their total daily calorie intake. The math is something like this: one can of soda is 150 calories. One pound of body fat is about 3500 calories. So one can of soda a day (150 calories x365 days) produces 15.6 pounds of additional fat per year.  A large amount of calories commonly consumed come in the form of juices and sodas, which are full of sugar—often in the form of fructose. Fructose–often called the fruit sugar– is a type of naturally occurring sugar found inmany fruits (berries, melons, apples), vegetables (beets, sweet potatoes, onions) and honey. Fructose is nearly twice as sweet as sucrose (table sugar) and is commonly used in processed foods partly because it is less expensive to produce than sucrose and it takes less of it to produce the same level of sweetness.

So how does fructose work in our body and why is it so deadly?, Glucose is the main type of sugar in the blood and is the major source of energy for the body’s cells. Unlike glucose, fructose does not stimulate insulin, nor leptin, the hormone that tells your brain you are full.  Fructose get metabolized entirely by our liver, eventually leading to what is known as metabolic syndrome, or pre-type 2 diabetes. Doctors are finding an alarming increase in diabetes in children.

If we compare the equivalent calories from glucose and fructose we can see the difference between the two in the way it is processed in the body.. Two slices of bread contains about 120 calories of glucose. Of that, 96 calories (80 percent ) is used by the cells and the liver takes up 24 calories. Most of that gets stored as glycogen; some gets converted to ATP (our main source of energy); and about ½ calorie of that is turned into VLDL (very low density lipoprotein). VLDL is a cholesterol transporter that has been linked to cardiovascular disease.

Compare that to 120 calories of sucrose from an 8-ounce glass of orange juice. Sucrose (table sugar) is composed of two sugar molecules—1/2 glucose and 1/2 fructose. So of the 120 calories, 60 are glucose in which about 40 calories get used by the body and 12 go to the liver. But all 60 calories of fructose get metabolized directly by the liver, for a total of 72 calories of sugar that get taken up by the liver. Once in the liver, fructose is metabolized much differently than glucose.  One of the byproducts of fructose metabolism is the waste product, uric acid, which your body disposes of through the urine.  However, excess uric acid is what causes not only gout, but high blood pressure as well. Some of the sugar won’t make it out and forms a fat droplet in the liver.

Excess fat in the liver leads to a disease known as non-alcoholic steatohepatitis (NASH). Much more of the fructose will be metabolized to VLDL, and much more will be turned into triglycerides.  The negative effects of excess fructose include hypertension, increased risk of heart attacks, pancreatitis, obesity, fatty liver, fetal insulin resistance, and addiction as well as all the diseases that are associated with type 2 diabetes and obesity.

Fructose changes the way your brain recognizes energy, all in a negative fashion —your brain gets the signal that you’re starving even though your fat cells are saying that you are full. In summary:

  • Fructose consumption has increased in the last 30 years and is a major contributor to the obesity epidemic.
  • Fructose is a carbohydrate that gets metabolized like a fat.
  • Thirty percent of the fructose ends up as fat, so a low-fat diet isn’t really low fat because the fructose/sucrose doubles as fat.
  • Hepatic fructose metabolism leads to all the manifestations of metabolic syndrome—hypertension, NASH, inflammation, obesity, leptin resistance promoting continued consumption, dyslipidemea, de novo lipogeneis
  • Fructose is a chronic hepatotoxin —“it’s alcohol without the buzz.”

So what about fruit? Doesn’t fruit have fructose? Of course it does, but fruit also has fiber. As Dr. Lusting says: “When God made the poison, he packaged it with the antidote.” Whenever fructose occurs in nature, there is also more fiber. Whole fruit also limits the amount of fructose one can consume. Most people will only eat one orange in a sitting, while a glass of orange juice may contain the juice of four or five oranges (with the fiber removed). Fiber reduces the rate of intestinal carbohydrate absorption and increases the speed of transit of intestinal contents to the ileum, which induce satiety and inhibits the absorption of free fatty acids in the colon. Fructose used in processed foods has no fiber.

To reduce one’s own intake of dangerous fructose, and to maintain a healthy weight, get rid of all sugared drinks, including juice. There are no healthy sweetened beverages. Read labels and buy products that do not contain corn syrup. Further protection from the dangers of ingesting too much fructose is found in regular exercise. Why is exercise important? It has little to do with the burning of calories, but rather it improves skeletal muscle sensitivity to insulin (brings insulin down) and reduces stress, thus your appetite decreases.  In addition, exercise increases your cells’ metabolism so the sugar doesn’t get turned into fat.

If you found this article helpful, please feel free to leave a comment or ask a question below.

    29 replies to "The Devil in the Fructose"

    • Christine Casey

      Hi Shannon & welcome to TSA!

      I luv this post b/c I’m one of those who have already realized the “danger” of HFCS, and as of late this past Summer, eliminated it from my diet and my teenage son’s diet (although he’s not too thrilled about giving up Coca-Cola, yet I’ve found we can purchase the bottled same that is from Mexico with cane sugar). It was amazing to me that within in a couple of weeks of eliminating HFCS from our diet (you would not believe how many products have this in it…even things that most of us think are “healthy”!) I found myself with more energy AND a side-benefit, some of that stubborn “belly fat” had begun to go away 😉 I appreciate you sharing, and hope that this info reaches out to more of us out there that are unaware of the danger in fructose.


      • Dr. Shannon Weeks

        Thanks so much Christine. I often tell my clients that if people didn’t eat sugar my practice would limited to acute injuries. Remember that fructose is half of cane sugar as well. The HFCS industry is right when they say it’s no different than sugar (aside from the genetically modified corn)-they’re both deadly in the long run.

        In good Health,

        Dr. Weeks

    • Donnie Miller

      Hi Shannon! I also recently have realized the danger of HFCS and eliminated all “soft drinks” from my diet.

      I have found that I do have much more energy than before and I have lost my “spare tire” (belly fat).

      My wife and I are trying to eat healthier this new year and hope that we can continue with this new lifestyle.

      Thanks again for this post…

      ~ Donnie

      • Dr. Shannon Weeks

        You’re welcome Donnie. Congrats to you and your wife for committing to a healthy lifestyle.

        Dr. Weeks

    • Pearly

      Hello Dr Shannon,

      This is such a great sharing ! Thank you. I really love every information in your post.

      I have many additional knowledge about fructose now. will tell my friends not to only think of taking less sugar. Beware of the word “fructose” on the label is as equally important.


    • Emily

      I am also aware of all the bad chemicals in our food. What is a shame is that the FDA is supporting all this bad stuff. Pretty soon, the only food we will be able to eat is over processed and genetically mutated.

      Support your local farmers so that they and you can fight for your health. Because when the last small farmer goes out of business you can say bye to healthy, and hello to famine.

    • Beth Hewitt

      Hi Shannon,

      This is a great read. Thanks for sharing this information. It amazingly sad how the Western World has slowly become larger and larger over a relatively short space of time.

      Beth 🙂

    • Wendy Hewlett

      This is an excellent article Dr. Weeks! I love how you showed the damage that drinking one can of soda a day can do. When we are making choices on a daily basis, we often think that one soda won’t make a difference. But, one soda every day DOES make a huge difference. It is so important for people to realize this so that they can make healthier choices. Every single one matters. There is no “Oh, I’ll just have this one. It won’t hurt.” They add up over time.

      Thanks for sharing this!


    • Steven Dean

      This is all very interesting to me. I have no idea on how we are consuming so much more fructose than we originally had today than in the past. I can only imagine that maybe the FDA are probably doing all this. If people just make foods taste how they originally should be; then we would be better off. But we come to be so spoiled and accustomed to unnatural sweeteners and flavors that food taste way to bland. I look at some of the foods that I eat an read on back of the labels of what a single teaspoon or table spoon adds up to being, which is alarming. Makes you think that when you eat something that you should eat a spoonful of this and a tablespoon of that to stay healthy. Sometimes when I think I’m eating something healthy it turns out to be just almost just as unhealthy as something that isn’t. Can’t win a losing battle I tell ya. Enjoyed this article you have a lot of great highlights here.

      Steven Dean

    • Guy Santeramo

      hi Shannon,

      Great post and great info.

      i remember back in the 90s most weight loss products contained fructose thinking that it was a better healthy form of sugar.


      Great blog.


    • Jenny

      I think it is absolutely amazing how much sugar (and fructose) we have in our diets, especially our kids. It seems that nearly everything a normal kid eats is packed with sugar. I have to stop and think throughout the day about how much sugar is in the food I’ve given my son, even in the savory foods. Definitely the biggest problem comes from packaged foods, so there is so much to say for homemade food!


    • Jeremiah M. Wean

      That is a real eye opener. As a high schooler I was diagnosed with hyperglycemia, I guess everyone is to some extent, but I was pretty bad. Passing out about 1 hour after eating. I had to go with a glycemic diet. The entire list of foods approved and amounts was able to fit on one page, at that time.

      To this day I still crave sugar very much. Thanks for reinforcing the need to keep it out of my diet.

    • Dr. Shannon Weeks

      Homemades definitely the key Jenny. One of my food rules is “never eat anything your grandmother wouldn’t recognize as food.”


      Dr. Weeks

    • Kimberly Castleberry

      Thanks for the great reminder about the trouble with Fructose. I read on it pretty extensively while I was avidly low-carbing and it makes a huge impact. My triglycerides had been out of wack (high) for several years, following two rounds of Accutane and had not come back down on their own. Low-Carbing brought them down very quickly back to a much better metabolic profile. You couldn’t argue with the lab results.

    • Dr. Shannon Weeks

      The medical community is slowly catching on that it’s sugar, not fat that increase triglycerides which in turn increases cardiovascular risk. Congrats on getting your health back. I love you’re blog by the way, I look forward to your posts.

    • Dr. Adam Sheck

      Thanks so much for sharing this. I was fortunate to be raised by a mother who didn’t believe in soda or even drinking water during a meal, so I never really developed a sweet tooth. I worry about my daughter (now 17), as she is exposed to so much more that is unhealthy then we were and it seems to get worse and worse. Education is a big key, so thanks so much for that.
      Take care,

    • Waldow

      My Mom and I just sat through a diabetes consultation for her with an RN specialist from her HMO. It was shocking to hear the RN to tell my sick Mom to essentially not worry about what she eats, but rather to just restrict the proportions. I asked him to at least discourage Glucerna shakes, the first 4/5 ingredients being starch and sugars, but was told “Oh no. Don’t read the label. Everything has that stuff in it. Glucerna is made for diabetics. Its OK.” The RN meant well, but I think this illustrates we are up against something more than a need for education.

      • Dr. Shannon Weeks

        Hi Shawn.

        I’m dumbfounded, the level of ignorance around this issue is astounding. Type 2 diabetes can be reversed in 30 days (depending on how much damage has already been done) on a strict Paleolithic diet. It’s not brains surgery, but the diabetes industry is a billion dollar giant and they are not eager to go out of business.

    • Melissa McCloud

      found this article so interesting, thank you dr shannon. when it came to sugar i simply thought: “fruit: good, HFCS: bad”. but i really enjoyed reading how the different sugar molecules are metabolized and how that affects us.

      i teach a (simple, non-science-y) nutrition class and highlight the sugar epidemic with the participants. i show a bag of sugar (which weighs 2-3 lbs) and represents how much sugar an american consumes in one week. but what’s so surprising is how much sugar an american consumed in ONE YEAR at the turn of the last century (1900): it’s just 5 lbs!!! so crazy!

    • Deb Augur

      Hi Dr. Weeks,

      Your article is a godsend to a lot of people not realizing the effects of sugar or HFCS. There’s so much of it in everything we consume (like salt!) that it’s incredibly difficult to cut down enough to make a difference, it seems.

      On the other hand, the pharmaceutical industry seems to combine their strategies with the sugar-rich food and beverage industries to pull the wool over our eyes.

      I was incredibly delighted that you advocate far more natural remedies because when all is said and done, it’s true… you are what you eat (and drink)!

    • Beth Allen

      I appreciate you sharing such important information, Shannon ~ and SO thorough! It is amazing how many people are uneducated and misinformed, sadly because of the fact that our nutrition information is political rather than scientific.

      So thank you for spreading this message about the dangers of fructose (and the misleading information about fat!) ~ this is one that needs to be spread far and wide!

    • Rosemary

      Dr Weeks, it strikes me there is a very serious problem with so many diets due to life style changes. Children spending to much time behind computers etc and diets have not changed to take these factors into account. It is great you wrote about this subject and the serious issue of the increase of diabetes.

    • Penelope

      I found your article extremely interesting and would like to share it with a friend. However I thing there is a mistake. When you are talking about a glass of orange juice with 120cal of sucrose. You go on to say it is made up half of glucose and half of sucrose. You then start talking about fructose. I think you mean half glucose and half fructose.

    • Mary Chavez

      Thank you for this article!

      I just left a sales seminar for products containing fructose which were supposed to be healthy and induce weight loss and offer superior tradition. Fructose was represented as a healthy ingredient that would not adversely affect blood sugar levels since it wasn’t high fructose corn syrup but derived from sources such as beets and pears. This didn’t sound right.

    • Eric

      Very good article! I am concerned about a product that has as one of the main ingredients Fructose. It is sold to P90X’ers and others who are seeking to loose weight, and get into shape. It is in their Shakeology, and other products. Is this safe to consume since most are consuming it after a workout? Will the body metabolize it safely? Their products are very popular right now.

    • john

      hi all, i am worried about eating more than the recommended servings of fruit per day, is this dangerous? Will this lead to type2 diabetes? Please help, anyone.
      thank you.

    • Victoria

      Thank you for the information. You explained that so well!!!

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