However, it occurred to me that there's another tactic which is currently used for evil that could be used for good: upselling. Make the fast-food restaurants stop upselling unhealthy things like fries and soda. You can still buy them, but you have to ask. Instead, restaurants could increase their profits by upselling healthy things. "You want fresh fruit with that?" Or carrot sticks, celery sticks, anything else that can be made into finger-food eaten the same way as fries. Offer water, tea, lemonade, etc. instead of soda.
Small changes, but easy to sustain, and thus more likely to work.