obesity diet vs reducing diet

obesity diet and reducing diet both are nouns.

Word	Noun	Adjective	Verb	Adverb
obesity diet	Yes	No	No	No
reducing diet	Yes	No	No	No

As nouns, obesity diet and reducing diet are synonyms defined as:

obesity diet and reducing diet: a diet designed to help you lose weight (especially fat)

obesity diet (noun)	reducing diet (noun)
a diet designed to help you lose weight (especially fat)	a diet designed to help you lose weight (especially fat)