Conventional wisdom has often stated that sparkling water is good for weight loss however, despite the obvious benefits of sparkling water for dieting, there are some recent studies that have shown that the carbonated beverage could increase ghrelin (the hunger hormone) production making you hungrier and resulting in weight gain.
Ultimately the question of whether or not sparkling water is good for weight loss is going to depend on your existing diet. If you’re replacing a full sugar fizzy beverage with it, and it hits the craving then sparkling water, is of course, going to be good for your diet.
However, if you’re trading it out for what was previously a non sparkling glass of water, it could be inadvertently making you more hungry. So, let’s go into the pros and cons of sparkling water and whether or not it’s actually good or bad for weight loss.
When Sparkling Water is Good for Weight Loss
Hydration - Staying hydrated is essential for overall health and can also support weight loss efforts. Sparkling water, just like still water, can help keep you hydrated. If the carbonation in sparkling water encourages you to drink more fluids throughout the day, it can contribute to your daily water intake. Dehydration can lead to various health issues, including fatigue, dry mouth, and difficulty concentrating. By staying adequately hydrated, you can support your body's natural functions and potentially enhance weight loss. 
Low-Calorie Alternative - For individuals who struggle to drink plain water, sparkling water can be a refreshing and low-calorie option. Unlike sugary sodas and fruit juices, sparkling water is typically free of added sugars and calories. By choosing unsweetened sparkling water instead of calorie-dense beverages, you can reduce your overall calorie intake and create a calorie deficit, which is crucial for weight loss. 
Satiation and Appetite Control - Drinking enough water can help you feel fuller for longer and may aid in appetite control. When you consume sparkling water, especially before or during meals, it can contribute to a sense of fullness, potentially reducing the amount of food you eat.  This can be particularly beneficial for individuals who struggle with overeating or mindless snacking. And it's likely that sparkling water is still better than not being properly hydrated, despite increasing grehlin.
Digestive Benefits - Some individuals experience digestive issues, such as constipation, which can hinder weight loss efforts. Sparkling water may offer relief from such symptoms. Research suggests that consuming carbonated beverages, including sparkling water, can help alleviate constipation by promoting regular bowel movements and reducing abdominal discomfort. By maintaining optimal digestive health, you can support your weight loss goals. 
How Could Sparkling Water Cause Weight Gain?
As we mentioned above there is some albeit relatively small evidence that carbon dioxide in drinks could increase ghrelin production. We’ll outline the study details below.
The Study That Shows Soda Water Causes Weight Gain
To investigate the effects of sparking water and carbonated beverages on weight gain, researchers conducted experiments on male rats and human participants. Male rats were divided into different groups and given various types of beverages over the course of a year. Stomach ex vivo experiments were also conducted to measure the levels of ghrelin, a hunger hormone, in response to different beverages. Additionally, 20 male students were involved in a study that examined their ghrelin levels after consuming different beverages. 
Sparkling Water Increases Grehlin
The results of the experiments on rats revealed a significant correlation between the consumption of gaseous beverages and weight gain. Rats that consumed carbonated drinks gained weight at a faster rate compared to those given regular degassed carbonated beverages or tap water. This weight gain was attributed to elevated levels of ghrelin, which stimulated increased food intake in the rats. Furthermore, the rats treated with gaseous drinks showed higher liver lipid accumulation compared to the control groups.
In the study involving human participants, the levels of ghrelin hormone were found to increase in healthy males after consuming carbonated beverages. This further supports the role of carbon dioxide gas in stimulating ghrelin release and triggering the hunger response.
Does Sparkling Water Cause Weight Gain?
The studies found that carbon dioxide gas in sparkling water can increase ghrelin production. Which in turn plays a crucial role in inducing weight gain and the onset of obesity.
As an increase in ghrelin levels makes people hungrier subsequently overeating. This mechanism applies to both rats and humans, highlighting the potential impact of sparkling water on weight management.
It is important to note that the effects of sparkling water on weight gain may vary depending on factors such as individual metabolism, overall diet, and lifestyle. Of course if you regularly consume sugary soda, swapping to sparkling water will likely lead to weight loss rather than weight gain.
1 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4901052/
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8163615/
3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4121911/
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908954/
5 - https://pubmed.ncbi.nlm.nih.gov/28228348/