This is partially true. There are many contributing reasons but this is one.
Acceptable answers could be A because if it's on the side people will feel less tempted to eat it and will eat less. C techinally could be correct but i don't think it's the answer.
Interesting enough, the byproduct of marijuana that actually is stored anywhere in the blood stream is also the main hallucinogenic and pain relief property THC. THC is interesting in that it will store itself in the bodies fat deposits.