I mean, if they did succeed they wouldn't still be here.
There is some documentation of confirmed fatalities from SN that you can review
here if you are interested. And just if you want it,
here are the confirmed non-fatalities as well, if you want more information and first-hand accounts of people who took SN and lived to tell the tale.
In general though, if you want to succeed with SN, it's better to do it on an empty stomach after a fast. It will help you process it a little faster. Additionally, certain foods can dilute/interact with SN in ways that make it less effective (Vitamin C, for example significantly lowers its effectiveness).
It's kinda gross too, but you are pretty likely to vomit if you take SN, and it's a lot easier on you if you are vomiting an empty stomach rather than the full meal you just ate.
With SN, you want to be deliberate in your process so that you can have the best chances of succeeding, and the best chances are if you are not on a full stomach. Having said that though, it's definitely not impossible to succeed with a full stomach. In the failures thread, there was someone who ate before taking SN, and they only failed because they were found before CTB.
I know that fasting can be annoying and painful, but it's a lot less painful than failing your attempt. Best of luck to you in your endeavors~