Was the prohibition on eating dinner health advice?
My recollection is the rule about not eating after noon was to stop monks going on alms round at inappropriate times of the day, including at night, where they could frighten lay people. You can research the 'Vinaya' for this. 

There certainly is a sutta where the Buddha states he enjoys good health by eating once a day but my recollection is that is not the rationale, which is why many monks today eat twice per day. 


  When these staple foods go beyond their time limit (i.e., after noon) a bhikkhu will incur an offence if he consumes them. The original
  story shows the complications that can arise from leaving the
  monastery at the wrong time:
  
  The 'group-of-seventeen' bhikkhus — another set of frequent misdoers — went out one afternoon to enjoy themselves at a festival outside the
  city. When lay people saw them they gave them a meal and food to take
  back to the monastery. The Buddha therefore laid down this rule:
  
  "Should any bhikkhu chew or consume staple or non- staple food at the wrong time, it is [an offence of Confession.]" (Paac. 37; BMC p.362)
  
  http://www.accesstoinsight.org/lib/authors/ariyesako/layguide.html#begging