One is unlikely to be successful changing our diets (8)
I believe the answer is:
outsider
'one is unlikely to be successful' is the definition.
I can't judge whether this defines the answer.
'changing our diets' is the wordplay.
'changing' indicates anagramming the letters.
'our'+'diets'='ourdiets'
'ourdiets' is an anagram of 'OUTSIDER'.
Can you help me to learn more?
(Other definitions for outsider that I've seen before include "Foreigner" , "not a favourite" , "1000/1 shot" , "expected to be unsuccessful" , "Not a member of the group" .)