Carbonated Water Consumption Linked to Reduced Snacking, Alcohol Intake, and Modest Weight Loss in Japanese Adults: Results of a 12-Week Randomized Trial

A randomized, open-label, placebo-controlled, parallel-group trial published in *Scientific Reports* examined the effects of daily carbonated water consumption on lifestyle behaviors and health indices in Japan. Forty-six healthy Japanese adults (20–64 years, BMI 23.0–<30.0) were allocated to ingest either carbonated water (4.3 ± 0.1 g CO2 per 500 g/day) or non-carbonated water for 12 weeks; 45 participants completed the protocol (carbonated n = 22; placebo n = 23). Primary outcomes included snacking frequency, alcohol intake, body weight, BMI, and liver-related enzymes.

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Obesity-related, lifestyle-associated diseases remain a leading public-health challenge in Japan, where dietary and drinking patterns significantly influence disease risk. Energy-free carbonated water has been proposed as a low-calorie alternative to sugary drinks and alcoholic beverages, yet empirical evidence on its sustained behavioral and physiological impact has been limited.

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• Baseline (Week 0): Enrollment, randomization, baseline assessments.

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• Week 4: Interim evaluation of snacking frequency.

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• Week 12: Final assessment of snacking frequency, alcohol consumption, anthropometry, and serum liver enzymes (AST, ALT).

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Compared with the placebo group, the carbonated water group exhibited:

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• A reduction in weekly snacking episodes of 1.39 times at week 4 (95 % CI –2.82 to –0.28; P = 0.018) and 1.49 times at week 12 (95 % CI –2.93 to –0.05; P = 0.049).

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• A decrease in alcohol intake of 24.44 g/week at week 12 (95 % CI –44.02 to –4.86; P = 0.019).

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• Modest weight loss of 0.72 kg (95 % CI –1.37 to –0.07; P = 0.036) and BMI reduction of 0.26 kg/m² (95 % CI –0.50 to –0.02; P = 0.037).

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• Lower serum AST by 4.05 U/L (95 % CI –7.57 to –0.53; P = 0.034) and ALT by 9.47 U/L (95 % CI –18.01 to –0.93; P = 0.026).

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No beverage-related adverse events were reported.

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The findings suggest that a simple, calorie-free beverage may influence eating and drinking habits, potentially supporting modest weight management and liver health in populations at risk for obesity-related conditions. If replicated, carbonated water could be incorporated into public-health recommendations as a non-pharmacologic strategy to curb excess caloric intake.

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The study authors conclude that daily carbonated water consumption “may be associated with favorable changes in snacking and alcohol consumption behaviors and modest improvements in selected anthropometric and liver-related indices.” They emphasize the exploratory nature of the analyses and advise cautious interpretation.

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Critics within the author team note several constraints: the trial’s open-label design, modest sample size, short duration, and lack of multiplicity adjustment for multiple outcomes. These factors limit the strength of causal inference and generalizability beyond the studied cohort.

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No comparable randomized trials of carbonated water in Japanese or other populations were cited, highlighting a gap in the literature. Replication with larger, blinded samples and longer follow-up is needed to confirm durability of effects.

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• “Energy-free carbonated water has been suggested to promote sensations of fullness and may serve as a low-caloric alternative to caloric foods or alcoholic beverages; however, evidence regarding its sustained effects on habitual behaviors and objective health indices is limited.” — Study Introduction

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• “These findings suggest that daily consumption of carbonated water may be associated with favorable changes in snacking and alcohol consumption behaviors and modest improvements in selected anthropometric and liver-related indices.” — Conclusion

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• “Given the exploratory nature of the analyses and multiple outcomes without multiplicity adjustment, findings should be interpreted cautiously.” — Conclusion

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The authors recommend larger, double-blind trials to verify behavioral and metabolic outcomes, explore dose-response relationships, and assess long-term safety. Integration of objective dietary monitoring could elucidate mechanisms underlying observed reductions in snacking and alcohol use.

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