I find the hardest part of eating healthy is at the time of making the choice of what to eat.
A.I could potentially suggest restaurant orders, grocery lists, and recipes. If I had confidence that the system had my best interets "at heart" and it had enough expert knowledge built in I'd probably let it make 95% of my diet choices and count myself lucky to make one less type of decision while improving my health.
These 'fake' relationships aren't new. Therapy, counseling, coaching, tutors etc. They _can_ be incredibly rewarding and fulfilling.