It has been known for a while that people who switch from regular soda to diet soda (and make no other changes) do not lose weight.
This is a crazy result given the calorie difference, so there must be something going on.
Somehow the body is reacting badly to the dissappoinment of not getting all the promised calories that it tasted. Either triggering cravings that drive people to make up the deficit elsewhere or causing the digestive system to change gear in some way.
It is now known that there are sweetness receptors in the gut, so this flow of what the body thinks is undigested sugar may make things go haywire. Anyway, it's not my field, but I find it interesting.
I think it's generally true that "people who do X (and make no other changes)" do not lose weight for all values of X except some very unhealthy things, and those unhealthy things are generally followed by rebound weight gain anyways.
Almost everything to do with weight loss verges on pseudo-science and the field is constantly flooded with misinformation from people peddling something. Focusing on weight loss as a goal in and of itself is thus pretty much always a road to pain anyways.
Worse, artificial sweeteners are used in animal farming to make animals gain more weight. This is due to a combination of factors, both increasing appetite as well as feed efficiency.
Somehow the body is reacting badly to the dissappoinment of not getting all the promised calories that it tasted. Either triggering cravings that drive people to make up the deficit elsewhere or causing the digestive system to change gear in some way. It is now known that there are sweetness receptors in the gut, so this flow of what the body thinks is undigested sugar may make things go haywire. Anyway, it's not my field, but I find it interesting.