To dream of being on a diet represents restrictions or limits you’ve placed on you self. You may not be doing something or thinking about something as much as you were before. You are limiting certain kinds of stimuli or enjoyment.
Concerns about overindulgence. Reducing bad habits or sexual interest. Feeling the need to be very serious about your lifestyle, habits, or addictions.
Alternatively, a diet may reflect self-punishment, self-control, or self-discipline. You are giving up something you believe is not healthy for you or trying to be more moderate about your choices.