Reconciling the Low- and No-Calorie Sweetener Debate
An evidence review of cardiometabolic outcomes.
Researchers at the University of Toronto have conducted an umbrella review of systematic reviews and meta-analyses to address the confusion surrounding low- and no-calorie sweeteners (LNCS) and their impact on health. The study examined evidence from both randomised controlled trials and observational cohort studies, comparing results using different analytical approaches, including naïve analyses versus bias-adjusted methodologies, to determine whether LNCS support or hinder cardiometabolic health and weight management.
Aim
The research team aimed to resolve the inconsistency in evidence that has led to conflicting dietary guidelines and public confusion about LNCS. Specifically, they sought to understand how different analytical methods influence conclusions about LNCS and cardiometabolic outcomes, including body weight, disease risk, and mortality.
Methods
The researchers conducted a comprehensive search of medical databases through December 2024, looking for systematic reviews and meta-analyses that used at least two analytical approaches:
For trials:
Naïve analysis: comparing LNCS to all comparators combined (sugar, water, placebo, usual diet)
Bias-adjusted analysis: comparing LNCS specifically to sugars (intended substitution) or water/placebo (reference substitution)
For cohort studies:
Naïve analysis: examining prevalent LNCS use at baseline
Bias-adjusted analysis: modelling changes in LNCS consumption over time or substitution for sugars/water, with adjustment for baseline body weight
They included six trial-based reviews covering approximately 24,500 participants and five cohort-based reviews covering nearly 2.8 million participants. The team assessed the certainty of evidence using GRADE criteria and extracted data on energy intake, body composition measures, glycemic control, blood pressure, cholesterol levels, and disease incidence.
Results
Trial Evidence: Consistent Benefits When Replacing Sugars
When trials lumped all comparators together (naïve approach), LNCS use was associated with reduced energy intake, body weight, and body fat. These benefits were primarily driven by studies where LNCS replaced sugars—the intended substitution scenario.
More importantly, when specifically comparing LNCS to sugar-sweetened beverages (bias-adjusted intended substitution), the evidence showed:
Reduced energy intake
Lower body weight and body fat
Reduced body mass index
Lower systolic blood pressure (when compared to water)
When LNCS replaced water or a placebo rather than sugar (reference substitution), results were essentially neutral across most outcomes, with only minor differences observed. This demonstrates that LNCS benefits depend on what they’re replacing—they help when substituting for calories, not when adding to water.
Cohort Evidence: Methodology Matters
The cohort study results revealed a striking pattern that explains much of the controversy:
Naïve analyses (simple comparisons of people who consumed LNCS versus those who didn’t) suggested harm:
Higher obesity risk
Increased type 2 diabetes incidence
Greater stroke risk
Higher cardiovascular and all-cause mortality
However, bias-adjusted analyses (accounting for changes in consumption over time and what LNCS replaced) painted a completely different picture:
Lower body weight and waist circumference
Reduced obesity incidence
Lower coronary heart disease risk
Reduced cardiovascular and all-cause mortality
This reversal occurs because naïve observational analyses are susceptible to reverse causality-people already gaining weight or developing disease may switch to LNCS in an attempt to manage their condition, making it appear that LNCS caused the problem rather than being adopted in response to it.
Evidence Certainty
The certainty of evidence ranged from very low to high across outcomes. Trial evidence generally showed moderate certainty, while cohort evidence certainty was typically low to very low due to limitations, including inconsistency between studies, imprecision, and potential confounding factors.
Key Takeaways
LNCS are useful when they replace calories, not when they replace water. If you’re choosing between a sugar-sweetened beverage and a zero-calorie alternative, the LNCS option supports weight management and doesn’t harm cardiometabolic health markers. However, LNCS don’t offer meaningful advantages over plain water.
The context of use matters more than the sweetener itself. LNCS work as part of a calorie reduction strategy—they’re tools for displacing sugar calories, particularly from beverages, which are the largest source of added sugars in most diets. They’re not magic bullets but rather practical alternatives when you want sweetness without the caloric load.
Don’t be misled by observational studies alone. Much of the negative press around LNCS comes from studies that simply compared LNCS users to non-users without accounting for why people choose LNCS in the first place. When researchers use proper methods to address these biases, the evidence aligns with what controlled trials show—modest benefits when used as sugar substitutes.
Practical application for training and nutrition. If you’re managing your weight or body composition, using LNCS-sweetened beverages instead of sugar-sweetened options can help reduce overall calorie intake without apparent negative health consequences. This can be particularly useful during fat loss phases or when trying to maintain leanness while still enjoying sweet-tasting beverages. The evidence suggests this approach supports, rather than hinders, your physique goals.
The bigger picture. This research reconciles what appeared to be contradictory evidence by showing that when you account for proper comparison groups and reduce bias in observational studies, the data consistently support LNCS as a viable strategy for reducing added sugar intake and supporting weight management—provided they’re used to replace sugary options rather than being consumed in addition to your normal diet.
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Reference
Sabrina Ayoub-Charette, Meaghan E. Kavanagh, Tauseef Ahmad Khan, and John L. Sievenpiper. 2025. Reconciling conflicting evidence on low- and no-calorie sweeteners and cardiometabolic outcomes: an umbrella review using naïve and bias-adjusted methods. Applied Physiology, Nutrition, and Metabolism. 50: 1-26. https://doi.org/10.1139/apnm-2025-0068
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