Is it possible my metabolism has increased after lip injections or am I crazy?

Thank you for your question.  Neither botox nor fillers cause your metabolism to be increased, I'm guessing the appointment threw you off your normal routine and that may have delayed your normal eating times/amount. 

Hunger has nothing to do with filler or botox injections, I have seen this with liposuction treatment.  Best, Dr. Emer.

Dermal or wrinkle fillers such as Juvederm or Restylane or Radiesse do not have any effect whatsoever on metabolism/hunger ; neither does Botox. Some people who have pain may feel like increasing food intake to help with pain.

My assumption is that you must have been a bit stressed or nervous about the procedure which kicked in some adrenaline and made you hungry immediately after. It's our own body's response to stress or angst. Not the fillers or Botox themselves. "This
answer has been solicited without seeing this patient and cannot be
held as true medical advice, but only opinion. Seek in-person treatment
with a trained medical professional for appropriate care."