I’m not familiar with this study, but I don’t have anything against diet soda. I think it is the healthier choice just because of the lack of sugar. In my opinion, and what works for me, is that fruit and veggies with some basic supplements are the way to go. Yes fruit has sugar, but it’s natural sugar and if eaten in moderation, it won’t change much. But you see mineral, vitamins, antioxidants etc that provide you energy and recoverability. Not that diet is bad it just doesnt have those in it.