Yacon Syrup and Weight Loss: Critical Review of Research

Yacon syrup is the latest superfood to hit the market with the promise of helping people lose weight. Dr. Oz, who featured yacon on his TV show, even asked the tantalizing question, “Could this be the weight loss game changer you’ve been looking for?” It turns out there is some research on yacon, and that will be the focus of this review. In addition, I’ll also look at the study Dr. Oz did on yacon and try to give an idea of who should not use it. I admit that I didn’t know about yacon syrup until it was brought to my attention by my niece, Lori—so I want to say thanks to her for the heads up on this.


What Is Yacon Syrup?

Yacon syrup comes from the roots of the yacon tree which grows in the Andes Mountains of South America. The tubers, which jut out from the roots of the tree, look like sweet potatoes. These tubers are a source of the soluble fiber, inulin, which in turn provides fructooligosaccharides (FOS). The scientific name for the plant is Smallanthus sonchifolius. Other names include Polymnia sonchifolia and Bolivian Sunroot. For those who were curious, yacon is pronounced “ya-cone.”


How Yacon Works?

Yacon syrup contains molecules called fructooligosaccharides (pronounced, fruuk-toe-oly-go-sack-a-rides) – or just FOS for short. The name sounds complicated but FOS are basically just fancy sugar molecules that are relatively small in size. One thing that makes FOS different is that we don’t break them down for energy very well. As such, FOS has less calories than regular sugar.


Fructooligosaccharides are actually a type of Prebiotic. You can think of prebiotics as the food of probiotic bacteria. So, even though we can’t digest/absorb a lot of the FOS, our probiotic bacteria can digest them, and in this way, FOS help keep friendly bacteria healthy. Currently it’s thought that the fructooligosaccharides are at the center of the weight loss effects of yacon syrup.


Tip. FOS are derived from the sugar, fructose. As such, foods (like fruits and vegetables) that have fructose also contain FOS. A few examples include onions, bananas, and garlic—although yacon is said have the most. FOS are even used in some foods to increase the fiber content. If you eat fiber-fortified cereals, like Fiber One, take a look at the ingredients list and you’ll see “inulin,” which is soluble fiber and a source of FOS.


Yacon Syrup Weight Loss Research

I wanted to see if there was any proof that yacon syrup helped people lose weight, so I searched the National Library of Medicine for:

  • Yacon weight loss
  • Yacon obesity
  • Smallanthus sonchifolius weight loss
  • Smallanthus sonchifolius

And I found the following relevant investigations:


Study 1

In 2009, a study was published titled, Yacon syrup: beneficial effects on obesity and insulin resistance in humans. Here’s a summary of the study:

  • The study involved 55 women (35 women completed the study) between the ages of 31–49.
  • The women were overweight with mildly high cholesterol and a history of constipation. The study lasted 4 months (120 days).
  • The women were randomly divided into 3 groups: a placebo group and two groups that received different amounts of yacon syrup. The women were advised to take the yacon 1 hour before meals.

Study Results

  • At the end of 120 days, women who received yacon syrup had lost an average about 34 pounds and about 4 inches off their waist. Body Mass Index was also significantly decreased.
  • Yacon syrup did not raise blood sugar levels. Women getting yacon syrup showed increased insulin sensitivity (their insulin worked better) than women getting the placebo.
  • As an aside, it’s possible that the improved insulin sensitivity could be due to weight loss rather than a direct effect of yacon syrup on insulin itself. More study is needed on this issue.
  • There were no changes in triglyceride levels or total cholesterol or HDL levels (good cholesterol).
  • A significant decrease in LDL (bad cholesterol) was seen in yacon syrup users.
  • Women who received yacon syrup also had an increased defecation frequency (3.5X) compared to those getting the placebo.


Study 2

In 2011, there was a study titled, Ipomoea batatas and Agarics blazei ameliorate diabetic disorders with therapeutic antioxidant potential in streptozotocin-induced diabetic rats, where researchers basically gave diabetic rats different plants to see what effect they might have on blood sugar, etc., when the rats were fed sugar. The plants they fed the rats were:

  • Smallanthus sonchifolius (yacon)
  • Ipomoea batatas (sweet potato)
  • Agaricus blazei (a type of mushroom)


Basically, they found that Smallanthus sonchifolius (yacon) was not able to reduce blood sugar, hemoglobin A1C (a marker for diabetes), insulin levels, or reduce body weight when the rats were fed sugar. Interestingly, both Ipomoea batatas and Agaricus blazei were shown to help diabetes in these rats.


The Dr. Oz Yacon Syrup Experiment

As most viewers of his TV show may know, Dr. Oz did his own experiment on yacon syrup. Here is a summary of that study based on how Dr. Oz described it on TV:

  • The study lasted 28 days and involved 60 women. The women were instructed to take a teaspoon of yacon syrup 3x a day before breakfast, lunch, and dinner.
  • The women were told not alter their diet or exercise programs.

The Results

  • 40 of 60 women completed the study
  • The women lost an average of 2.9 lbs
  • Women lost an average of 1.9 inches from their waists
  • 73% lost weight (that is, 29 women out of the 40 who completed the study)
  • 68% said they would recommend yacon syrup (that is, 27 out of 40 women who completed the study)

While this was not a peer-reviewed study, it’s interesting that women did lose weight. Here is some of the good and bad about the Dr. Oz experiment:

The Good:

  • The women lost weight, inches, and BMI.
  • The women were told to eat and exercise as they normally would. In theory, this means the only thing the women did was take yacon syrup. This could lend evidence that yacon had a real effect.

The Not-So-Good:

  • There was no placebo group so compare the results to.
  • 20 of the 60 women dropped out of the study. That’s a 30% drop-out rate. That’s odd since the study didn’t seem to be hard to do.
  • The study only contained women. What about us men? Don’t we get any Dr. Oz luv?
  • Dr. Oz said 73% of women lost weight. This also means 29% of women did not lose weight with yacon syrup. Why?


One potential pitfall to the Dr. Oz study was that the women knew that this experiment was for the Dr. Oz Show. This is significant because women LOVE Dr. Oz. They love him to pieces! Because of this, it’s possible that the women may have worked harder at losing weight―even though they were told not to―because they knew they might be on TV and didn’t want to disappoint Dr. Oz.

Drawbacks or not, I think the Dr. Oz experiment adds something to the discussion because there isn’t much yacon research out there right now and it showed some modest weight loss in a relatively short period of time. Losing about 3 pounds in a month is in line with guidelines for healthy weight loss.

The Woman’s World Study

The February 17th 2014 issue of Woman’s World magazine (page 18) also had story about yacon syrup. They conducted their own experiment where they had readers (they didn’t say how many) eat a 1500 calorie per day diet along with a teaspoon of yacon syrup before each meal. They said the people – presumably only women – lost 8 pounds in 7 days.

While I can applaud their efforts, this was not the best study because there was no placebo group and most healthy people will lose weight just by eating 1500 calories per day. Therefore, its hard to say what caused the 8 pounds of weight loss – the yacon syrup or the 1500 calorie per day diet?

Yacon Syrup and Testosterone

During my investigation, I uncovered a 2013 study titled, The spermatogenic effect of yacon extract and its constituents and their inhibition effect of testosterone metabolism. In this study, rats were given extracts of yacon tubers and yacon leaves. Researchers noted that yacon tubers increased not only sperm count but also testosterone levels.

Based on this rat study, I predict that yacon will be an ingredient in supplements for men with “low T.” For now, what I can say is that more research is needed to see if yacon raises testosterone or sperm count in people.

This would make an interesting research topic for any college students reading this (hint, hint…).


Yacon Syrup Side Effects

For healthy people with no medical issues, I think yacon syrup is probably safe. Reported side effects from taking too much of the syrup include:

  • diarrhea
  • abdominal bloating
  • nausea
  • cramping
  • gas

For those who are constipated, yacon syrup appears to help some go to the bathroom more regularly; however, for those who have diarrhea, it will make things worse.

Remember, yacon syrup has fiber, so too much too soon might send you to the bathroom.

People with irritable bowel syndrome (IBS) should be careful with yacon as its FOS content may have an effect on symptoms.

I located a 2010 case report of an anaphylaxis after eating yacon root in a 55-year-old woman. Anaphylaxis is a severe life-threatening allergic reaction. To be safe, those who think they are allergic to yacon or related plants should probably steer clear of it.

One person – who left a comment below – stated that yacon syrup lowered HDL (good cholesterol) and raised LDL (bad cholesterol) levels. That’s not good because if its true, it may mean that yacon syrup might increase heart disease risk. Honestly, I never saw references to this side effect in any of the studies and I’m not sure how common it might be. I mention it just in case, in the hopes that others who see this might comment below and let me know if this other happened to them.

Yacon may reduce the absorption of some minerals (like iron). As such, until more is known, it may be wise to not take yacon at the same time multivitamins are taken.

Since FOS are derived from fructose and since fructose can raise triglyceride levels (fats in the blood), some may wonder if yacon syrup raises triglycerides? So far this has not been observed. In fact, animal and human studies appear to show yacon reduces triglycerides. In the 2009 human study summarized above, yacon syrup was also shown to reduce LDL levels (bad cholesterol).

When picking a supplement, until more is known, make sure that it does not contain yacon leaves or extracts of the leaves, which may be toxic. The supplement should only contain the syrup derived from the roots of the plant.


How Much Might Work?

If you saw the Dr. Oz segment on TV (here’s the video, in case you didn’t), he recommended 1 teaspoon before or with each meal. That’s 3 teaspoons a day for most of us. While that sounds appropriate to me, I’d say be more conservative, and try only 1–2 teaspoons per day for the first week, just to see what happens, before ramping it up to 3 teaspoons per day (we are all different, after all).

After you are using it 3 times a day, try experimenting with taking it 30–60 minutes before you eat to see if that helps it work better―and let me know. I’m curious.


What Kind Of Yacon Syrup Is Best?

If yacon syrup is going to work, I believe the product should contain only the syrup and nothing else. I say this because supplement companies have a tendency to combine trendy/”sexy” ingredients together in an attempt to try to make something work better.  As such, look for “100% yacon syrup” such as these products which has gotten a lot of positive feedback (read the comments).

While I have not tasted yacon syrup at the time of writing this review, one audience member of the Dr. Oz show called it “candy in a bottle”—which says to me it probably tastes pretty good.

There are many different yacon supplements out there. Currently I have no proof any are the “best.” As long as it says 100% on the label, I think all products are probably equal.

For those who are curious, there are yacon syrup capsules. Would these work the same? Honestly, I’m not sure. If you have tried the capsules and they worked―or didn’t―leave a comment and let me know.

As I was researching this stuff I noticed that several products made claims that yacon was a “metabolism booster.” Words like this are just marketing hype and should be disregarded. Technically, eating anything raises metabolism.


Does Yacon Syrup Work?

Right now, there appears to be a single human study showing yacon syrup might help people lose weight. That study―which showed 34 pounds of weight loss―sounds impressive, but when we look at the average weight loss over the 120-day duration of the study, it’s about 3.5 pounds per month. While that is good, I mention this to put the weight loss into better perspective so people don’t expect amazing, overnight results if they try it.

The Dr. Oz study, while not perfect, also lends some evidence as well, although I’d like to see a few other studies before passing a final judgment. As such, I will say that I’m cautiously optimistic that some people might notice an effect. I do feel the effects will be seen best in those who exercise and pay attention to the calories they are eating. If you’ve tried it and it worked—or didn’t—leave a comment, because I’m curious to know what people think about this.

Here’s all the brands on Amazon for those who want to see what others are saying.

What do you think?


  1. Kim says

    Hi Joe, As usual you did a great job on the Yucon Syrup craze. I found the same research. I may have missed it in the research since I looked at this stuff a year ago, before Dr. Oz. I agree about the women not wanting to disappoint Dr. Oz to be on his show.

    I also did not see who was keeping track of these women when it came to actually recording when and if they actually took the syrup. Who recorded their measurements? My understanding was that the women did. That is speculative in itself.

    The research in my opinion in most all of the studies was very vague, and again no placebo.

    You are right about the fiber as well. Everyone digest fiber differently. It can be life threatening to many people if they take a full dose of anything right out of the gate just because a company says so. I always recommend to my clients less is more for a few days, then if you feel ok, you can up the dosage a bit for a few days, and adjust to the recommended dosage as they feel they can.

    Anyway, just thought I would chime in here again. Dr. Oz is a great guy, but and I say but, every time he recommends something everyone runs out to buy it, without thinking first, should I ask a knowledgeable dietician, A Dr who has a background in healthy eating, you get my gist. How ask you?

    People are making themselves sicker than ever taking all this stuff. They can’t digest it all. Then I have to get them off the majority of it, so they can get their digestion working normally again.
    Blessings, Kim

  2. Amanda Hop says

    I’ll admit, I’m new to reading dietary labels/ nutritional information, but every yacon syrup Amazon sells, the label says 0 fiber. Is the fiber hidden in the sugar content? Is the sugar content the FOS? I’m still confused.

    • Joe says

      Amanda, its actually the fructooligosaccharides (FOS) not the “fiber” that’s supposed to be power of yacon syrup. this is a type of sugar and that is probably why you dont see any fiber on labels.

      Here is something Ive written on my personal site about weight loss supplements also

      if you try yacon and it works – or doesn’t – do let me know.

  3. Ksy says

    Saw Dr. O episode about yacon. Wanted to lose weight and lower cholesterol. Tried it and immediately lost cravings for sugar and carbs. Definitely curbed appetite.

    Some days had to make myself eat. Took teaspoon before each meal. Ate healthy. Lost weight. But, bad cholesterol went up and good went down.

    Wish there were more studies. Stocked up on certified organic when demand made it hard to find. Would love to keep taking it but concerned it may have an opposite effect on me with cholesterol.

    Off of it for 6 weeks, and cholesterol dropped significantly. Went back on again on lower dose and cholesterol went up.

    Thanks for your report and giving us a place to discuss.

    • Joe says

      Ksy, I believe are the first to ever say that Yacon syrup raised LDL and lowered HDL levels. I never read anything about this when I investigated this product. I’m going to ask around and see if anyone else has noticed this effect. Ive updated my review with what you said just. hopefully others will reply and let us know what their cholesterol levels were before and after using yacon.

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