I wonder about the same thing in general for people taking this drug. I think the reason some people are overweight is because their body is asking for that much food not for the sake of caloies but to get adequate nutrition. (I am not sure what fraction this would apply to.)

I think there are a lot of theories about why people eat too much, and all of them apply to some people. I have been eating "healthier" for months, including about 5x as much vegetables as I had been previously into my eating, cutting back (but not eliminating) desserts. I still found that I did not lose weight because I was eating too much. I don't believe it was because I was not getting adequate nutrition - I just wanted food.