In Australia, a person can only call themselves a dietitian if they are accredited by the Dietitians Association of Australia (DAA).
Therefore, in Australia, all dietitians are considered to be nutritionists however, nutritionists without a dietetics qualification cannot take on the specialised role of a dietitian.
However some people who describe themselves as nutritionists (and not Accredited Practising Dietitians) have not attained their qualifications from an accredited program at an approved tertiary institution (which includes substantial theory along with supervised and assessed professional practice in clinical nutrition). Indeed, there is no industry specific assessing authority that assesses the qualifications of nutritionists who are not dietitians.
The services that non-accredited nutritionist offer do not attract Medicare rebates (or DVA rebates).
Hence, by following the advice of Accredited Practising Dietitians, you are assured of getting the most up-to-date, comprehensive, University-trained evidence-based care available.