Willpower and discipline don’t seem to be what keeps other countries skinnier than the US (and most of them are also getting fatter…) so I don’t know why we expect that to get the US out of this mess.
Evidence: people from skinnier countries move here and consistently get fatter. It’s a societal/environmental problem, if we’re talking about “what would a policy fix look like?” and not “what can I personally try to do to save myself despite being up against a societal/environmental problem?”