Keto, for one (4)
I believe the answer is:
diet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">keto for one</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that ketogenic diet is a type of high-fat diet)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for diet that I've seen before include "A disciplined food regime" , "International conference" , "Legislative assembly; food regimen" , "Range of food eaten" , "Food and drink regularly consumed" .)