So, the first step was campaign finance reform, taking away some of the incentive for politicians to pander to big companies instead of the health of our nation. Once that's out of the way, we can target another big systemic issue.
2) Stop subsidizing corn.
A big reason that America has such bad health outcomes compared to all those other industrialized countries that pay less for health care is that Americans are fat. Fat, lazy Americans eating lots of meat and drinking soda get those really expensive chronic illnesses like diabetes and hypertension. This raises costs for everyone, since we're in this system together. A major reason that so many people eat meat and sweets is that those foods are so cheap. An apple costs more than a candy bar. Juice costs more than soda (juice is also high in calories, but fructose is easier on your pancreas than dextrose). Also, impulsive and ignorant people would rather get fast food or some other form of processed junk than take half an hour to cook. Cooking healthy food can actually be very inexpensive, but it takes a little time, and most Americans would rather do something else.
So, how would ending corn subsidies lead to healthier eating? American corn is produced in far greater quantities than needed because the feds pay the big farm conglomerates to do it. There is so much unnecessary corn that the price is very low to buy it. Since it's so cheap, it gets fed to chickens, pigs, and cows to get them big and fat at a low cost. It also gets turned into corn syrup to keep our sodas and candy cheap (the price of sugar is artificially increased in America by federal tariffs on sugar imports, keeping down competition with corn). So, heavily because of this one crop subsidy, meat and sweets are very cheap and plentiful in the US.
There are other consequences. Since so many fields get devoted to corn (which does not require crop rotation like some other crops), less of other crops are grown that are not subsidized. More corn for animals and sweets (and fuel) results in fewer carrots and spinach and peas for humans. A smaller supply of those healthy foods for people means that they cost more.
So, ending the corn subsidy would make meat and sweets more expensive, and probably other healthy foods cheaper and more prevalent. There would be an economic incentive for people to eat food that is better for them, and restaurants would serve smaller portions of meat to keep costs low. Diabetes and heart disease rates, etc..., would fall, and life spans would increase again.
Animals might get switched to a different food, which would then be taken from humans, but I don't know what that would be. There would be other effects of the change, as well.
If the price of corn went up to the same level as that of other countries that do not subsidize (Mexico), those countries would stop importing the poor-tasting, standardized, potentially dangerous American corn that is wiping out their indigenous corn strains and making them slaves to the entirely unethical Monsanto. More expensive American corn would lead to more preservation of genetically diverse corn, which would protect our global supply from disease or insect. It would also let "heirloom" corn strains compete, which taste better and are safer to eat.