Anecdotal evidence here. Throughout my life I have been on diets various time, never because of extreme obesity but like a lot of people in IT, I do not get enough movement and over time gain weight. Thus every 2 years or so I end up going on a diet to lose the weight that I have gained, and in the past I used to mainly drink (sparkling) water when I did this, and always had positive results.
Now I have been trying to diet again but instead of replacing my sugary drinks with the "zero" version of them (coke zero to be specific) I _seem_ to lose weight slower.
Could be a lot more factors in play, but my wife has been suggestion that even those zero drinks have a negative effect on the diet, so she will enjoy this article :-)