A sweet-tasting syrup that can help you lose weight? It seems almost too good to be true.

But this is exactly what some health gurus and marketers are saying about yacon syrup, which recently became popular as a weight loss aid.

In contrast to most weight loss supplements, it does have some actual human-based research to back up the claims.

This article takes an objective look at yacon syrup and reviews the studies behind it.

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Yacon syrup is extracted from the roots of the yacon plant.

The yacon plant, also called Smallanthus sonchifolius, grows natively in the Andes mountains in South America.

This plant has been eaten and used for medicinal purposes for hundreds of years in South America.

People there believed it to have powerful medicinal properties, leading to improvements in diabetes and helping with kidney and digestive disorders (1).

The juice from the roots is extracted, then filtered and evaporated in a chemical-free manufacturing process that resembles the way maple syrup is made.

The final product is a sweet-tasting syrup, with a dark color and a consistency similar to molasses.

Summary Yacon syrup is extracted from the roots of the yacon plant. It’s a sweet-tasting syrup with a look and consistency similar to molasses.

Yacon syrup is one of the best dietary sources of fructooligosaccharides (FOS), a type of fructan. Fructans are a category of soluble dietary fiber.

The exact amount may vary between batches, but yacon syrup contains roughly 40–50% fructans.

It also contains some digestible sugars though. These include fructose, glucose and sucrose, which are responsible for the sweet taste of the syrup. The rest is fructooligosaccharides and a fiber called inulin (2).

Because a large part of yacon syrup isn't digested, it has only a third of the caloric value of sugar, about 133 calories per 100 grams, or 20 calories per tablespoon.

For this reason, it can be used as a low-calorie alternative to sugar.

The fructans eventually reach the large intestine, where they feed the friendly bacteria in the digestive system. This is where yacon syrup works its magic.

The friendly bacteria in the gut are actually incredibly important for your health. Having the right types is associated with a lower risk of diabetes, better immunity and improved brain function to name a few (3, 4, 5, 6, 7).

When the bacteria digest the fructans, they also produce short-chain fatty acids that have powerful anti-obesity effects, at least in rats (8, 9).

There is also some evidence that fructans can lower the hunger hormone ghrelin, helping reduce appetite (10, 11).

Keep in mind that yacon is not the only food that contains fructans. They’re also found in smaller amounts in artichokes, onions, garlic, leeks and various other plant foods.

Summary The active ingredients in yacon syrup are fructans, primarily fructooligosaccharides, which feed the friendly bacteria in the intestine and lead to various beneficial effects on metabolism.

Pretty much all claims behind yacon syrup are based on one study:

Yacon syrup: Beneficial effects on obesity and insulin resistance in humans.

This study was a double-blind, placebo-controlled clinical trial. The participants were 55 obese women with cholesterol problems and a history of constipation.

The women were split into two groups. A total of 40 women took yacon syrup, while 15 women took another type of syrup with no active ingredients (placebo).

All of them were advised to eat a low-fat diet and mildly restrict calories. The study went on for about four months.

At the end of the study, the women in the yacon syrup group had lost 33 pounds (15 kg) on average. At the same time, the placebo group gained an average of 3.5 pounds (1.6 kg).

The study also found reductions in waist circumference.

The women in the yacon syrup group lost 3.9 inches, or 10 centimeters, of their waist circumference. No significant changes were seen in the placebo group.

There were several other effects noted in the yacon syrup group:

  • Their body mass index (BMI) decreased from 34 to 28 (from obese to overweight).
  • Their stool frequency increased from 0.28 per day to 0.99 per day, effectively curing them of constipation.
  • Fasting insulin levels went down by 42%.
  • Insulin resistance, a major risk factor for diabetes and heart disease, was reduced by 67%.
  • LDL (the "bad") cholesterol went from 137 mg/dL to 97.5 mg/dL (a 29% decrease).

Overall, the women who took yacon syrup had dramatic improvements in both body weight and metabolic health, while the women taking the placebo stayed pretty much the same.

However, before getting too excited, keep in mind that this is just one fairly small study. It’s highly likely that other studies will lead to different results.

Studies on other types of soluble fiber have shown some amount of weight loss, but not nearly this impressive (12, 13).

More studies need to confirm these results before any claims can be made about the effectiveness of yacon syrup for weight loss.

It's also important to keep in mind that even if yacon syrup truly works this well, the effect is probably short-term. Many things can help people lose weight. Keeping it off is the real challenge.

Summary In one study, women taking yacon syrup lost 33 pounds (15 kg) over a period of 120 days. They also saw dramatic improvements in metabolic health.

Due to its high fructan content, yacon syrup has various other health benefits (14).

This includes reduced symptoms of constipation, which is a very common health problem.

In one study, yacon syrup reduced the transit time through the digestive tract from 60 to 40 hours and increased stool frequency from 1.1 to 1.3 per day (15).

There is also some evidence that it can lower blood sugar, although this needs to be studied a lot more.

Fructooligosaccharides effectively function as soluble, fermentable fibers, which have various other benefits. Yacon syrup is also high in antioxidants and potassium (16).

Summary Yacon syrup is effective against constipation and may lower blood sugar levels. It’s also high in antioxidants and potassium.

Yacon syrup can have some side effects if you eat too much at a time.

It’s very similar to the side effects you get by eating more soluble fiber than you're used to. When a lot of it reaches the intestine, it can cause excess gas production.

This can lead to flatulence, diarrhea, nausea and digestive discomfort. For this reason, it’s best to start out with a small amount and then work your way up.

If you have problems with diarrhea, you might want to avoid yacon syrup altogether. It can make things worse.

Fructans belong to a class of fibers known as FODMAPs. This makes yacon syrup unsuitable for people intolerant to FODMAPs, including those with irritable bowel syndrome (17).

The dosage used in the most prominent study was roughly 10 grams of fructans per day, which amounts to about 4–5 teaspoons (20–25 grams) of yacon syrup per day.

In the aforementioned study, the syrup was taken about one hour before meals. An effective dosage may be 1–2 teaspoons (5–10 grams) before breakfast, lunch and dinner. Start with 1 gram.

You can also use yacon syrup as a sweetener, but keep in mind that you cannot cook or bake with it because a high temperature (anything over 248°F or 120°C) will break down the structure of the fructooligosaccharides (18).

It’s possible that the timing matters, too. Taking it 30–60 minutes before a meal may be a more effective way to reduce appetite than eating it with a meal.

If you want to try it out, then make sure to get 100% pure yacon syrup. There shouldn't be anything else added to it.

It’s also possible to get other supplements containing fructans, most of which are much cheaper than yacon syrup. Whether these supplements will have the same effect is not known.

Summary Yacon syrup is very high in FODMAPs and not suitable for everyone. High amounts may cause stomach pain and diarrhea. Start with 1 gram a day and gradually increase the amount you take.

A sweet-tasting syrup from the Andes that can help you lose as much weight as an extreme weight loss diet?

You know what they say. If it seems too good to be true, it probably isn't true.

That being said, the results of the one prominent study are promising.

Although yacon syrup is far from being scientifically proven to work, it may be worth a shot as a healthier syrup alternative.

It might turn out to be an effective tool for short-term weight loss, but don't expect it to be a permanent solution to your weight problems.