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Limited evidenceWeight management

Yacon Syrup

Yacon syrup is essentially a fructooligosaccharide syrup — a prebiotic fibre with real effects on satiety and bowel habit. The single trial that made it a weight-loss phenomenon has never been replicated, and it is still a sugar-containing syrup.

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What the science says

  • Causes weight loss Limited evidence

    The trial behind the hype ran 120 days in obese, mildly dyslipidemic premenopausal women at 0.14–0.29 g fructooligosaccharides/kg/day and reported significant decreases in body weight, waist circumference and BMI. No subsequent study has reproduced anything close: a 2025 systematic review of the last decade found only 7 trials totalling 161 participants, and none replicated that magnitude of weight loss.

  • Improves insulin sensitivity Limited evidence

    The original trial reported lower fasting insulin and HOMA-IR, and the 2025 review found reductions in fasting insulin, HOMA-IR and LDL cholesterol across the small literature. Acute postprandial glucose results were inconsistent and appeared to depend on each participant's baseline gut microbiota — a plausible explanation for why the effect does not travel between populations.

  • Increases satiety and bowel regularity Moderate evidence

    This is the most consistent finding and the least surprising: fructooligosaccharides reliably increase defecation frequency, shorten intestinal transit time and raise reported satiety. It is the standard prebiotic-fibre effect, available from cheaper sources such as inulin.

Dosage & safety

Studied doseStudies identified 0.14 g fructooligosaccharides/kg/day as the well-tolerated dose (about 10 g FOS, roughly 20–40 g of syrup for a 70 kg adult); 0.29 g/kg/day produced unacceptable GI symptoms. Typical retail label servings of 1–2 teaspoons (about 5–14 g of syrup) deliver considerably less FOS than the trials used.
SafetyDose-dependent bloating, flatulence, cramping and diarrhoea are the main issue and the main reason people stop; symptoms often ease with continued use. Fructooligosaccharides are a FODMAP — avoid if you have IBS with fermentable-carbohydrate sensitivity, SIBO or fructose malabsorption. Yacon syrup still contains free fructose and glucose alongside FOS, so it is not calorie-free and is not a zero-impact sweetener for people with diabetes. No safety data beyond about four months of use. Not studied in pregnancy or in children.

How to take it

TimingTiming does not matter; spreading it across meals is gentler than one large dose.
With food?With food.
Worth knowingBuild up over a week or two — the bloating is dose-dependent and usually settles, but a sudden jump reliably brings it back.

Interactions

With other supplements

  • inulin, GOS and other prebiotic fibres

    Additive fermentation, so gas, bloating and cramping stack quickly. count the total fibre dose rather than each product separately

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does yacon syrup help you lose weight?

The weight-loss claim for yacon syrup rests on a single 120-day trial in obese women that has never been replicated (limited evidence). A 2025 review found only 7 trials totalling 161 participants, none reproducing that magnitude of weight loss.

What does yacon syrup actually do?

Yacon syrup is essentially a fructooligosaccharide (FOS) syrup, and its most consistent effect is the standard prebiotic one: more frequent bowel movements, faster transit and greater satiety (moderate evidence). The same effect is available from cheaper fibres such as inulin.

How much yacon syrup should I take per day?

Studies found about 0.14 g of FOS per kg per day well tolerated, roughly 20-40 g of yacon syrup for a 70 kg adult, while 0.29 g/kg/day caused unacceptable gut symptoms. Build up over a week or two and spread it across meals.

Is yacon syrup safe for diabetics or people with IBS?

Yacon syrup still contains free fructose and glucose, so it is not calorie-free or a zero-impact sweetener for people with diabetes. FOS is a FODMAP, so avoid yacon syrup if you have IBS with fermentable-carbohydrate sensitivity, SIBO or fructose malabsorption.

Scientific references

Where to buy

Zint, Organics, Yacon Syrup, Prebiotic Sweetener, 8 fl oz (236 ml)

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