... which will probably never be repeated.
https://www.medscape.com/viewarticle/900797?src=wnl_edit_tpal&uac=291226FK&impID=1714149&faf=1 I think that study is about "low calorie" rather than Low carb, though they do mention ketones.
The authors of the ‘study’ write in the discussion section: "This study represents observational data and is not a clinical trial; however, randomised trials of low carbohydrate diets on mortality are not practical because of the long duration of study required. Another limitation of this study is that diet was only assessed at two time intervals, spanning a 6-year period, and dietary patterns could change during 25 years."In other words they can't prove anything.