Oooh fun! A new meta-analysis of artificial sweeteners and weight loss. The conclusion? Meh. But wait! There's a fundamental problem here. Let's look at it. 1/ bmj.com/content/364/bm…
There are 2 kinds of studies, observational and clinical trials. And, for artificial sweeteners, they get very different results. Out in the world, people who use them tend to weigh more than people who don't. See this 2018 review. ncbi.nlm.nih.gov/pubmed/29570245 
This is probably a case of reverse causality - the more dissatisfied you are with your weight, the more likely you are to use artificial sweeteners. Also, since many nutrition pros frown on them, they may be a proxy for bad dieting strategies.
But in random controlled trials, people using artificial sweeteners tend to lose more weight than people assigned to regular sugar. Here's a 2015 review that aligns with the 2018 review above. ncbi.nlm.nih.gov/pubmed/25609450
The new BMJ review kinda lumps them all together, and of course you get meh because they cancel out. The authors do note that, in the RCTs, overweight people lose more weight with artificial sweeteners.
I don't think nutrition pros should frown on artificial sweeteners, since even minimally effective weight loss tools are thin on the ground. And, yes, we can talk about metabolic effects too. Another thread for another day. THE END
