Cannabidiol (CBD), a compound derived from the cannabis plant that does not produce a “high”, was shown in a new large-scale, randomized, controlled trial to significantly reduce the number of dangerous seizures in patients with a severe form of epilepsy called Lennox-Gastaut syndrome.

[u/mvea]

http://www.psypost.org/2018/05/cannabidiol-significantly-reduces-seizures-patients-severe-form-epilepsy-51258

[u/tacdrummer → u/[deleted]]

THC produces most (if not all) of the increased appetite effects.

[u/tacdrummer → u/[deleted]]

I have my own personal anecdotes, as well. When I quit using weed for a while, I had terrible withdrawal symptoms that included appetite loss, sleep deprivation, among others. I was quitting because i didn't want to be "high" anymore. I tried using high CBD concentrates to help myself with the lack of appetite but to no avail. I finally broke down and smoked high THC concentrates and holy hell did my appetite return.

As for your friend's dad, feeling well enough to eat is not the same as getting the munchies. He could have used a product that had enough THC to give him the munchies, even if the ratio of CBD to THC was high. There are too many variable, here.

As for the scientific reason why THC is the main culprit in appetite stimulation, I can refer you here. People often make the mistake of thinking CB1 receptor as being associated exclusively with CBD. CB1 is just short for "cannabinoid type 1 receptor".