It is interesting to look at Adverse Reactions occurring in Placebo-Controlled Clinical Trials in the PDR Information...
In this case, there were two groups - one who took the
Wellbutrin and the other who took a placebo (no treatment).
Weight gain occurred in 13.6% of the Wellbutrin patients and 22.7% of the placebo patients (which is probably the evidence supporting the claim in the advertising campaign)
but...
Appetite increase occurred in 3.7% of the Wellbutrin patients and only 2.2% of the placebo patients???