Sparkling water may offer a modest assist for people trying to lose weight, according to research published in BMJ Nutrition Prevention & Health. The proposed benefits involve increased fullness and changes in how red blood cells absorb and metabolize glucose.

Carbonated drinks such as seltzer and sparkling water can provide a lower sugar alternative to soft drinks. Research has also suggested these bubbly beverages could speed digestion, another factor that may support weight loss.

The study focused on carbon dioxide, or CO2, in sparkling water. Researchers suggested that the CO2 may promote weight loss by enhancing glucose uptake and metabolism in red blood cells, although the expected effect is small.

The work was built on research conducted in 2004 involving hemodialysis, a process used during kidney dialysis. During hemodialysis, blood is filtered to remove waste and excess water, according to the study.

CO2 enters the blood during that process, similar to what happens when someone drinks carbonated water. Researchers found that the carbon in these beverages may assist the absorption of glucose, potentially contributing to weight loss.

The study offered cautious support for that possibility, stating: ‘The CO2 in carbonated water may support weight loss,’ It also warned that sparkling water should be part of a broader approach to healthy living, rather than the primary tool used for losing weight.

The researchers were equally clear that no beverage can replace the foundations of sustainable weight management. As the study stated: ‘A balanced diet and regular physical activity remain crucial components of sustainable weight management’.

Sparkling water may also influence appetite through the release of dissolved gas in the stomach. The resulting expansion can produce a feeling of fullness, which may reduce hunger and make carbonated water useful as an appetite suppressant.

The study explained: ‘Distension of the gastric antrum [the lower part of the stomach] due to the release of dissolved gas from carbonated water induces satiety, which may cause further satiety and gastric motility, thereby reducing hunger,’ This possible benefit applies to plain carbonated water, not every fizzy drink.

Weight loss and lifestyle coach Emily Morse said the difference between sparkling and still water is unlikely to transform anyone’s results. Personal preference may ultimately matter more because the proposed weight loss benefit from either option is very small.

Morse said: ‘Sparkling or carbonated water may potentially “assist” someone in losing weight due to the glucose uptake of the CO2, but whether you are drinking still or sparkling water in a weight-loss journey, it mainly will come down to your personal preference, as the weight loss benefit for either is so small,’

She was not surprised that carbonated water was associated with greater fullness. When someone is consuming fewer calories to lose weight, a low calorie carbonated beverage may make the stomach feel full and could help prevent cravings.

Still, the researchers cautioned against expecting pounds to disappear because of a change in beverage choice. The study said the benefits are ‘so small that it is difficult to expect weight loss effects solely from the CO2 in carbonated water,’

Carbonated drinks can also produce unpleasant digestive effects for some people. Morse said people may experience ‘the feeling of being bloated or causing gas within someone, due to the carbon dioxide,’

The wide range of sparkling water products available also means consumers must consider what else is included in the drink. Morse advised choosing options without added sugars, artificial sweeteners or other additives.

Anyone who dislikes sparkling water can continue drinking still water without worrying about missing a major weight loss advantage. Morse emphasized that sufficient hydration can substantially help a weight loss journey, so the better choice is whichever type of water works best for the individual.