It says so here.
I always feel a little weird talking about this. I don’t argue that there are health concerns that can be exacerbated by obesity, but I also would hate to see an extreme emphasis placed on losing weight. Teaching children (and adults) good eating/exercise habits? Cool! But some people are large, and they will be large despite their eating/exercise habits. We have enough fat-shaming.
Interestingly, the AMA also voted to support:
the idea of using revenue from taxes on sugar-sweetened sodas as one way to help pay for obesity-fighting programs. But the group stopped short of fully endorsing such taxes.