Highlights:
- Adults’ sweet taste preferences are remarkably stable. A six-month intervention with low, regular, or high exposure to sweet-tasting foods in the diet did not change how much people liked sweetness or how intensely they perceived it.
- Dietary sweetness exposure did not influence eating behaviour or health outcomes. No differences were found in calorie intake, body weight, metabolic markers, or food choices between groups exposed to different levels of sweetness.
- The trial results challenge public health recommendations that propose reducing exposure to sweetness to lower sweet preferences and prevent weight gain.
Understanding how our diet shapes our taste preferences is a central question in nutrition science. Sweet taste, in particular, has gained substantial research interest because of its biological roots. We know that humans’ appetite for sweet taste is innate, expressed even before birth, and observed across all ages and cultures around the world.
However, despite widespread assumptions, little high-quality research has examined whether regularly consuming more or less sweet-tasting foods can meaningfully alter how much we enjoy sweetness or how sensitive we are to it. The Sweet Tooth Trial1, a new large-scale randomised controlled trial (RCT) published in the American Journal of Clinical Nutrition, was conducted to fill this gap. By tightly controlling participants’ exposure to sweetness in the diet over six months and tracking detailed sensory, behavioral, and metabolic outcomes, the researchers aimed to answer a fundamental scientific question: Does long-term exposure to sweetness change the way adults perceive and prefer sweet taste?
What they found challenges the prevailing “sweet tooth” hypothesis, which claims that reducing intake of sweet-tasting foods will diminish our liking for sweetness, ultimately lowering sugar intake, reducing calorie consumption, and helping prevent weight gain.
Testing the “Sweet Tooth” hypothesis with a long-term trial design
The Sweet Tooth trial was designed to be one of the most comprehensive studies to date investigating whether long-term exposure to sweet taste shapes preference for sweetness or influences eating behavior and health outcomes. In this parallel-design RCT, 180 healthy adults were randomly assigned to follow one of three diets for six months:
- A diet with low exposure to sweet-tasting foods and beverages
- A diet with regular/ typical exposure to sweet-tasting foods and beverages
- A diet with high exposure to sweet-tasting foods and beverages, sweetened with both sugars and low/no calorie sweeteners
About half of each participant’s food intake was provided by the researchers, ensuring tight control over dietary sweetness levels. Participants’ sweet taste liking, perceived sweetness intensity, food choices, calorie intake, body weight, and metabolic biomarkers were measured at multiple time points during and after the intervention (follow up). Compliance to the intervention was verified using monthly 24-hour dietary recalls and urinary biomarkers, confirming clear differences in sugar and sweetener intake among the groups.
Sweet taste preferences prove surprisingly stable
Despite the substantial differences in dietary sweetness exposure, the results were clear: neither low nor high dietary sweetness exposure changed participants’ liking for sweet taste. Across all three groups, sweet taste liking remained stable over the six-month intervention. Participants continued to prefer familiar sweet foods over unfamiliar ones, but this pattern was unaffected by their assigned diet.
Sweetness perception, which is the intensity with which individuals perceived sweet tastes, was also unchanged. Whether participants consumed very few sweet-tasting foods in their diet or a large amount of them, their sensory response to sweetness remained the same.
Interestingly, once the study ended, all participants naturally returned to their baseline level of sweet food intake, a pattern that continued throughout the follow-up period. This suggests that sweet taste habits and preferences in adults are remarkably stable and not easily altered by dietary manipulation.
No significant effects on eating behaviour, body weight, or metabolic health ouctomes
The study also found no differences between groups in food choice or energy intake; no changes in body weight or body composition; and no group differences in blood glucose, insulin, HbA1c, or lipid profile, including blood cholesterol and triglycerides.
Findings that challenge current public health recommendations
The study’s conclusion is clear: altering how much sweetness adults consume does not meaningfully change what they prefer, how much they eat, or key indicators of health. This finding directly challenges existing public health recommendations that advocate reducing exposure to sweet-tasting foods in order to decrease sweet preferences and, ultimately, lower obesity risk. According to this large, long-term clinical trial, such strategies may not produce the intended results.
Instead, the evidence suggests that adults maintain a stable preference for sweetness regardless of how much or how little sweetness they consume. As a result, policies aimed specifically at reducing overall exposure to sweetness, not only from sugars but also from low/no calorie sweeteners, may need to be re-evaluated.
What this means moving forward in light of the collective literature
The Sweet Tooth trial provides strong, high-quality evidence that sweetness exposure alone is not a driver of excessive sugar intake, weight gain, or metabolic effects. And it is not the first study that challenges this widespread assumption. Previous shorter-term studies2 have found similar effects, as confirmed in published systematic3 and comprehensive literature reviews4. Similarly, preliminary results from another major trial by the Monell Center and the USDA5, which tested whether people who adopt a low-sugar diet will come to taste foods/beverages as sweeter and to prefer less sugar, indicate that diet manipulation had no statistically significant effect on either sweetness intensity or most-liked concentration of sucrose at any time-point.
As the conversation about nutrition policy evolves, these findings highlight the need for strategies grounded in robust scientific data rather than assumptions about how the human palate responds to sweetness.