Aah you're using the wrong search button - that one searches the whole site so as you found you get all diets lol
If you go back the the syn values forum main page where it lists the thread names. Then look at the sticky section. At the top right hand side of that section there is a blue button below the page numbers that says "search this forum". Use that one, and it appears on all the sub forums, and it will only give you results for the forum you are in and any sub-forums it has. So do a search in the recipe sub-forum and you get results from that one but also the winter and summer recipe sub-forums.