"The munchies" have unpleasant sequelae...

Exactly what is going on here appears to be more complicated than that. For example: https://www.medicalnewstoday.com/articles/325050

Title: Marijuana users less likely to be overweight or have obesity

Opening line: New research finds that, despite the common phenomenon of having “the munchies” after using marijuana, cannabis users tend to weigh less and are less likely to be obese.

This involved 33k participants in the US, so at least one order of magnitude smaller and in a different context.