An article from the Norwegian Institute of Public Health claims that studies showing weight gain from artifical sweetener consumption are generally of poor quality, and that they remain silent about cause and effect.
It seems more likely that weight gain causes artifical sweeteners to be consumed than the other way around. It also seems likely that any lack of weight loss is caused by subconscious calorie substitution rather than the sweeteners themselves. Cutting calories makes you hungry.
2) This is the article in question:
It further accuses the large American artificial sweetener metastudies of cherry picking the source studies.
When people send me articles from dubious websites like sweetpoison.com, I'm tempted to conclude that they are extremely gullible, or perhaps young and inexperienced.
3) You can never trust anything you read unless you know who said it. It's extremely important to be aware of who's talking when it comes to politics, science, religion and other hot-button topics. Any time anyone starts making interesting statements, it's time to check who said it, what their qualifications are, and how good their reputation is. As a general rule, boring statements are true, while exciting statements are opinions at best (and inflammatory lies at their worst).