Drinking a glass of water before a meal is a well-known tip for anyone wanting to eat less.
But now scientists believe swapping still for sparkling may be even more helpful for losing weight.
The bubbles in carbonated water could help reduce blood sugar and speed up metabolism, research found.
Doctors compared the process of drinking fizzy water with haemodialysis, when blood is filtered to remove waste and excess water when the kidneys no longer can.
This process turns blood alkaline, which primarily produces carbon dioxide or CO2.
Similarly, the CO2 in fizzy water is absorbed through the stomach lining and is rapidly converted to bicarbonate in red blood cells.
This speeds up glucose absorption by activating key enzymes in red blood cells, according to the findings published in BMJ Nutrition Prevention & Health.
Blood sugar levels fall during this process, suggesting that fizzy water may indirectly promote weight loss by enhancing the uptake and use of blood sugar.
Scientists now believe swapping still for sparkling water may be even more helpful for losing weight (file image)
Scientists say the CO2 in fizzy water is absorbed through the stomach lining and is rapidly converted to bicarbonate in red blood cells (file image)
Lead author, Dr Akira Takahashi, of the dialysis centre, Tesseikai Neurosurgery Hospital, Japan, said effects are small so drinking it alone will not be sufficient to shed the pounds.
Dr Takahashi said: ‘Given this minimal glucose reduction, the impact of COɼ in carbonated water is not a standalone solution for weight loss.
A balanced diet and regular physical activity remain crucial components of sustainable weight management.’
Drinking carbonated water can have some effects on the digestive system, particularly for people with sensitive stomachs or pre-existing gastrointestinal conditions, experts warned.
They suggested more research is needed before it can be recommended for therapeutic use.
Commenting on the analysis, Professor Sumantra Ray, of the NNEdPro Global Institute for Food, Nutrition and Health, said: ‘Any potential benefits must be weighed up against the potential harms of carbonated drinks which may contain sodium, glucose, or other additives.’
