Does sparkling water help with weight loss?

Maybe a little, and the whole case rests on one small trial. In a 12-week randomized trial of 45 Japanese adults with a BMI from 23 to just under 30, drinking 500 g a day of carbonated water cut body weight by 1.6 lb (0.72 kg) more than still water (95% CI 0.07 to 1.37). Participants knew which water they were drinking, and both drinks were supplied by the soft drink company Asahi. We found no meta-analysis or systematic review of carbonated water and body weight.

Unsettled. A single open-label trial of 45 people, with a confidence interval that nearly reaches zero, is a lead and not an answer. Nobody has repeated it, nobody has tested it in people with obesity, and the shorter meal studies disagree on whether the fizz makes people eat less at all.

What the trials found

The one trial that measured weight

The 12-week trial is the only one we found that ran longer than a day. Alongside the 1.6 lb (0.72 kg), BMI fell by 0.26 kg/m2 more on carbonated water (95% CI 0.02 to 0.50). The authors also reported fewer snacks and less alcohol in the carbonated group. Those habits came from daily questionnaires that people filled in knowing which drink they had, because, in the authors' words, blinding was not feasible due to the sensory characteristics of carbonation. Weight itself was measured, so the 1.6 lb (0.72 kg) is firmer than the explanation for it.

Fullness right after the drink

In a crossover trial of 13 young women, 8.5 fl oz (250 ml) of carbonated water raised fullness and lowered hunger ratings compared with plain water. Those ratings covered 45 minutes, and the study did not measure what the women ate afterward.

Whether people then eat less

Here the results split. In a crossover trial of 30 adults, a more heavily carbonated sweet drink raised fullness and lowered intake at lunch, with no effect on satiety after lunch or on what people ate for the rest of the day. That drink contained sugar, so it was not plain sparkling water. In 10 healthy adults, 10 fl oz (300 ml) of a calorie-free carbonated drink before a meal made the stomach larger on MRI and did not change how much food they ate, whether the meal was solid or liquid. In 8 healthy volunteers, carbonated water did not change how fast the stomach emptied a meal, only where the meal sat inside it.

The headline about blood sugar

Myth. The widely shared claim that fizzy water burns sugar and so causes weight loss traces to a 2025 brief report with no new human data. It proposed that carbon dioxide speeds glucose use in red blood cells, and its own author wrote that the amount is so small that weight loss from the CO2 alone is hard to expect.

Who should be careful

The cautions below come from laboratory, animal and expert evidence, and they concern teeth, reflux and flavored versions.

Not for everyone. Flavored sparkling waters are a different product for your teeth. In laboratory tests, flavored sparkling waters from the UK market had a pH of 2.7 to 3.3 and dissolved tooth mineral as much as or more than pure orange juice, at 89 to 143 percent of its erosive potential. It matters most for children and for people who sip them all day. Plain sparkling mineral waters, in a separate laboratory study on human teeth, dissolved enamel only slightly more than still water and about one hundred times less than soft drinks.

If you have reflux-like symptoms, a 2024 expert consensus reached full agreement on advising patients to limit carbonated beverages. That advice covers fizzy drinks in general, and we found no trial of plain sparkling water in reflux.

In rats given carbonated soft drinks for about a year, weight rose faster than in rats on degassed drinks or tap water, and the authors linked this to higher levels of ghrelin, a hunger hormone. That was animal data with soft drinks. It runs the other way from the human trial above, and no one has tested it with plain sparkling water in people over weeks.

What expert bodies say

We found no agency that rates carbonation itself for weight. The US CDC suggests adding a splash of 100% juice to plain sparkling water as a low-calorie drink, as a swap for sugary drinks. Any benefit in that advice comes from what the sparkling water replaces, and the CDC does not claim that the bubbles cause weight loss.

More on the drink itself is on the sparkling water page.

How we searched

What would change this answer

• A second trial of plain sparkling water and weight, larger and longer than 12 weeks, ideally in people with obesity and with follow-up after the drinking stops. We found none registered on ClinicalTrials.gov.
• A way to blind the comparison, or at least to measure snacking and alcohol by something other than a diary filled in by people who know which drink they have.
• A trial of flavored sparkling water, the version most people buy, since it is the one with the clearest tooth concern.
• A test in people, over weeks, of the ghrelin signal seen in rats.

Sources

1. ev-spw-01 · Randomized controlled trial(s) · randomized open-label placebo-controlled parallel-group trial · n = 45
   At week 12, modest decreases were observed in body weight and body mass index (BMI) compared with placebo (body weight: -0.72 kg; 95% CI - 1.37 to - 0.07; P = 0.036; BMI: -0.26 kg/m²; 95% CI - 0.50 to - 0.02; P = 0.037).
   
   Who: healthy Japanese adults aged 20-64 years with BMI 23.0 to under 30.0
   Effect: body weight -1.6 lb (95% CI -3 to -0.15; metric: -0.72 kg, -1.37 to -0.07); BMI -0.26 kg/m2 (-0.50 to -0.02); snacking -1.49 times/week (-2.93 to -0.05) at week 12
   Certainty: Single small open-label trial; exploratory outcomes without multiplicity adjustment; carbonated and still water both supplied by Asahi Soft Drinks; 4.3 g CO2 per 500 g.
   Sci Rep, 2026 · checked 2026-10-07 · we read the abstract
2. ev-spw-02 · Randomized controlled trial(s) · randomized open-label placebo-controlled parallel-group trial, limitations section · n = 45
   First, the study employed an open-label design because blinding was not feasible due to the perceptible sensory characteristics of carbonation.
   
   Who: healthy Japanese adults aged 20-64 years with BMI 23.0 to under 30.0
   Effect: open-label design; snacking and alcohol by daily questionnaire
   Certainty: Weight was measured, but the behavioral outcomes that explain it were self-reported without blinding.
   Sci Rep, 2026 · checked 2026-10-07 · we read the fulltext
3. ev-spw-03 · Randomized controlled trial(s) · randomized within-subject crossover trial · n = 30
   There were no significant effects on satiety following lunch or on intakes for the rest of the day.
   
   Who: non-obese subjects (fifteen women, fifteen men)
   Effect: medium (2.5 volumes) and high (3.7 volumes) vs low (1.7 volumes) carbonation in a 14 fl oz (400 ml) sugar-sweetened preload: higher satiety and lower lunch intake (P < 0.05); no effect after lunch
   Certainty: Single-meal study with a sugared drink, not plain water; no weight outcome.
   Br J Nutr, 2008 · checked 2026-10-07 · we read the abstract
4. ev-spw-04 · Randomized controlled trial(s) · randomized crossover trial with MRI gastric volume · n = 10
   The increase in gastric volume following a 300 ml pre-meal carbonated beverage did not affect food intake whether a solid or liquid meal was given.
   
   Who: ten healthy subjects (4 women, aged 22-30 years; BMI 23 ± 1)
   Effect: total intake at maximum satiety, solid meal: water 783, still drink 837, carbonated 774 calories (no difference)
   Certainty: Very small sample; single meal eaten at a fixed rate to maximum satiety.
   Nutr J, 2011 · checked 2026-10-07 · we read the abstract
5. ev-spw-05 · Randomized controlled trial(s) · randomized crossover modified sham-feeding trial · n = 13
   After ingestion, significantly increased fullness and decreased hunger ratings were observed in the CW group.
   
   Who: thirteen young women after an overnight fast
   Effect: significantly higher fullness and lower hunger after carbonated water; also transiently after carbonated sham-feeding
   Certainty: Ratings over 45 minutes; no food intake or weight outcome.
   J Nutr Sci Vitaminol (Tokyo), 2017 · checked 2026-10-07 · we read the abstract
6. ev-spw-06 · Randomized controlled trial(s) · randomized crossover trial, radiolabelled meal · n = 8
   In conclusion, carbonated water did not alter overall gastric emptying but profoundly modified intragastric distribution of the meal.
   
   Who: eight healthy volunteers
   Effect: identical solid and liquid emptying; proximal stomach solids 74% vs 56% with carbonated vs still water
   Certainty: Tiny mechanistic trial; no appetite or intake outcome.
   Dig Dis Sci, 1997 · checked 2026-10-07 · we read the abstract
7. ev-spw-07 · Laboratory or animal data · brief report, mechanistic hypothesis · n = —
   However, the amount is so small that it is difficult to expect weight loss effects solely from the CO2 in carbonated water.
   
   Who: no participants; theoretical comparison with hemodialysis data from 2004
   Effect: no measured weight or glucose outcome in people drinking carbonated water
   Certainty: No new human data; the widely reported 'fizzy water aids weight loss' headline rests on this paper. The author also warns carbonated water may affect blood glucose readings.
   BMJ Nutrition, Prevention & Health, 2025, 8(1):e001108 · checked 2026-10-07 · we read the abstract
8. ev-spw-08 · Laboratory or animal data · animal study with an acute human ghrelin measurement · n = 20 (human part)
   Here, we show that rats consuming gaseous beverages over a period of around 1 year gain weight at a faster rate than controls on regular degassed carbonated beverage or tap water.
   
   Who: male rats over about one year; plus 20 healthy male students tested acutely for ghrelin
   Effect: faster weight gain, more food intake and liver fat in rats on gaseous drinks; higher ghrelin in 20 men after carbonated drinks
   Certainty: Animal data with soft drinks, not plain sparkling water; the human part measured ghrelin only, not intake or weight. Contrasts with the human RCT (ev-spw-01).
   Obes Res Clin Pract, 2017 · checked 2026-10-07 · we read the abstract
9. ev-spw-09 · Laboratory or animal data · in vitro dissolution study · n = —
   Sparkling mineral waters showed slightly greater dissolution than still waters, but levels remained low and were of the order of one hundred times less than the comparator soft drinks.
   
   Who: still and sparkling mineral waters and comparator soft drinks, extracted human teeth and hydroxyapatite
   Effect: enamel dissolution about one hundred times lower than comparator soft drinks
   Certainty: Laboratory data; no flavored waters in this set.
   Journal of Oral Rehabilitation, 2001, 28(8):766-772 · checked 2026-10-07 · we read the abstract
10. ev-spw-10 · Laboratory or animal data · in vitro dissolution study · n = —
    In the hydroxyapatite dissolution assay, all of the waters demonstrated erosive potential (89-143%) similar to or greater than that of pure orange juice, an established erosive drink.
    
    Who: a selection of flavored sparkling water drinks from the UK market
    Effect: pH 2.74-3.34; erosive potential 89-143% of pure orange juice
    Certainty: Laboratory data; matters most for children and frequent sippers.
    International Journal of Paediatric Dentistry, 2007, 17(2):86-91 · checked 2026-10-07 · we read the abstract
11. ev-spw-11 · Position of an expert body · Delphi consensus with GRADE rating · n = —
    Eleven statements achieved the strongest (100%) agreement: five are related to diet and include identification and avoidance of dietary triggers, limiting alcohol, coffee and carbonated beverages, and advising patients troubled by postprandial symptoms not to overeat; the remaining six statements concern advice around smoking cessation, weight loss, raising the head-of-the-bed, avoiding recumbency after meals, stress reduction and alginate use.
    
    Who: patients with reflux-like symptoms
    Effect: limiting carbonated beverages among 11 statements with 100% agreement
    Certainty: Covers carbonated beverages in general; no trial of plain sparkling water in reflux.
    Eur J Gastroenterol Hepatol, 2024 · checked 2026-10-07 · we read the abstract
12. ev-spw-12 · Position of an expert body · agency guidance · n = —
    Add a splash of 100% juice to plain sparkling water for a refreshing, low-calorie drink.
    
    Who: US public
    Effect: swap advice; no claim that sparkling water itself causes weight loss
    Certainty: Benefit comes from replacing sugary drinks, not from carbonation. Page last reviewed 5 March 2026.
    US CDC, Rethink Your Drink, Healthy Weight and Growth, 2026 · checked 2026-10-07 · we read the section