There is a recent study making rounds that sparked more conversation about sparkling water than anything since seltzer became a cultural phenomenon. Published in BMJ Nutrition, Prevention & Health in January 2025, Japanese physician Dr. Akira Takahashi proposed that carbonated water might have a small but real effect on metabolism, beyond just replacing soda.
ABC News covered it. CNN covered it. ScienceAlert covered it. Everyone had an opinion.
So here is what the study actually found, what the researchers themselves cautioned, and what the genuinely reliable evidence says about sparkling water and weight loss.
Quick answer: Sparkling water is not a magic weight loss tool on its own. Dr. Takahashi’s research suggests only a minimal effect on metabolism from carbonation, and even that is highly contested. Where sparkling water genuinely helps with weight management is in what it replaces. Replacing two cans of sugary soda daily with plain seltzer cuts roughly 280 to 480 calories. That math is simple, real, and highly effective.
What the 2025 BMJ Study Actually Found
Dr. Takahashi’s paper, published in BMJ Nutrition, Prevention & Health (doi: 10.1136/bmjnph-2024-001108), analyzed glucose uptake by red blood cells. During hemodialysis procedures where $CO_2$ enters the bloodstream, the gas increases the blood’s pH slightly. Takahashi’s analysis suggested this mild pH shift accelerates glucose absorption by red blood cells, potentially reducing overall blood sugar levels.
In plain terms: drinking carbonated water might theoretically help your body process blood sugar slightly faster.
However, the warnings from the scientific community were immediate:
- ScienceAlert quoted Takahashi directly: “The amount is so small that it is difficult to expect weight loss effects solely from the $CO_2$ in carbonated water.”
- ABC News chief medical correspondent Dr. Chanda Narula agreed that while the chemistry is real, calling it a weight loss breakthrough is a stretch.
- CNN’s dietitian source Lori Welstead from the University of Chicago Medicine summarized it precisely: “Substituting zero-calorie fizzy water to replace caloric drinks may aid weight loss as part of a calorie-controlled diet by reducing calorie intake.”
The Satiety Debate: Does Carbonation Suppress Appetite?
The results on whether carbonation helps you feel full are mixed:
- Dr. Takahashi’s paper referenced satiety data showing carbonated water temporarily increased feelings of fullness and decreased hunger ratings immediately after drinking. The mechanical expansion of gas in the stomach triggers stretch receptors, sending temporary signals of fullness to the brain.
- Conversely, a 2017 study on rats (referenced in CNN’s coverage) suggested carbonation might increase ghrelin (the hunger hormone), potentially stimulating appetite. However, health professionals note that this study was conducted on rats and a tiny sample of 20 humans, and has never been successfully replicated.
For most people, a cold glass of seltzer before a meal provides a temporary feeling of fullness that can naturally limit portion sizes, though the effect varies by individual.
The Hydration Connection
One of the most common mistakes in weight management is misinterpreting thirst as hunger. When your body is mildly dehydrated, it triggers signals that are easily mistaken for food cravings, leading to unnecessary snacking.
Gabby Zeagler, a clinical dietitian quoted in Healthline’s coverage of the BMJ study, notes: “If someone is drinking seltzer all day long, this will also increase their hydration level, which helps support metabolism and will likely reduce the amount of times someone may mistake a feeling of thirst for hunger and lessen the amount of snacking they might do.”
Because seltzer offers a crisp, zesty mouthfeel, many people find it easier to drink in large volumes throughout the day than flat tap water.
Which Sparkling Water is Best for Weight Loss?
If you are using seltzer as a tool for weight management, keep these category differences in mind:
- 🟢 Best Choices (True Zeroes): Plain seltzers or zero-sweetener flavored options (LaCroix, Bubly, Waterloo, Polar, ALDI Belle Vie, Whole Foods 365). These add zero calories, zero sodium, and zero sweeteners to your day.
- 🟡 Moderate Choices: Spindrift. Squeezed fruit juice adds 3 to 17 calories per can. While completely healthy, these calories can add up if you drink a 6-pack daily.
- 🔴 Worst Choices: Sweetened sparkling waters (like Sparkling Ice or ALDI Sparkling Frost). While zero-calorie, the intense artificial sweetness (sucralose) keeps your brain calibrated to crave sweet things, making it harder to break sugar habits.
The Bloating Caveat
The carbon dioxide gas that makes seltzer fizzy can expand in the digestive tract, causing temporary bloating, distension, and gas. For individuals with IBS (Irritable Bowel Syndrome) or GERD (acid reflux), carbonation can exacerbate symptoms. If you want the hydration benefits of seltzer without the gas, letting the pour sit open for a few minutes allows some of the $CO_2$ to dissipate safely.
🥤 Soda Swap Deficit Calculator
Enter your current daily soda consumption to see how many calories and pounds of body fat you would save in a year by swapping to sparkling water!
References
- Takahashi, A. (2025). “Can carbonated water support weight loss?” BMJ Nutrition, Prevention & Health. doi:10.1136/bmjnph-2024-001108.
- ScienceAlert. “A Modest Weight Loss Boost Might Be Hiding in Your Glass of Water.” sciencealert.com. January 2025.
- Technology Networks. “Can Sparkling Water Aid Weight Loss? Researchers and Dieticians Are Still Split.” technologynetworks.com. January 2025.
- Healthline. “Could Your Sparkling Water Help You Lose Weight?” healthline.com. January 2025.
- ABC News. “What to know about sparkling water and weight loss, according to new study.” abcnews.com. January 2025.
- CNN. “Carbonated waters and weight loss: Don’t expect too much.” cnn.com. January 2025.
- ScienceDaily. “Can sparkling water boost metabolism and help with weight loss?” sciencedaily.com. April 2026.