The simple answer: in context of your question, nothing
First of all, the U.S. government never mandated masks. This is really important. It recommended masks, but there was never a federal mandate. Why? Because of the 10th Amendment.
The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people. (Source)
There is nothing in the Constitution that specifically allows the federal government power over health care issues, nor anything that specifically prohibits the States from power over health care issues. The Federal government literally does not have the authority to mandate masks or to mandate what food anyone eats.1
I am by no stretch of the imagination an attorney, but I wouldn't be surprised that one of the reasons the Affordable Care Act (ACA or Obamacare) can exist is because it doesn't address health care — it addresses insurance premiums. This is really important. The U.S. Constitution, Article I, Section 8, states:
To regulate Commerce with foreign Nations, and among the several States... (Source)
In other words, the Federal government cannot force the individual to live a healthy life, but the Federal government can use the Commerce clause to create an economic path to healthy living. It was a neat trick of the law. But it's (generally speaking and without specific argument) Constitutional.
Therefore, the federal government cannot force any individual to do anything unless that specific authority is granted to the federal government in the Constitution. Mandating masks and food are not, so the government cannot mandate either.
But then there's that pesky Commerce clause...
Theoretically the feds could use the Commerce clause in a way similar to the ACA to forbid anyone from transporting unhealthy foods across state lines — such as candy. They could use it to forbid the transport of raw materials that would make unhealthy foods across state lines — so long as it could be proven the raw material is good for nothing other than unhealthy food (good luck with that... too much sugar is unhealthy, but what's "too much sugar?").
Of course, all this could be circumvented with an Amendment...
Finally, as was pointed out in another question — the government has tried simply amending the Constitution to force people to live healthier lives. The 18th Amendment, also known as "prohibition." The idea was was politically so strongly supported that it was made a Constitutional Amendment, which means it didn't need to abide by either the Commerce clause or the Tenth Amendment — it was a law to itself, equal with all the others. It failed so miserably that another amendment (the 21st) was created to nullify it.
The fundamental problem with any kind of mandate like these is that what you perceive to be a reasonable morality is almost certainly going to be rejected as such by someone else. That, of course, is what it means to be free.2
1 Thank goodness. The idea that anyone should have the right to tell me that I can't get fat is so utterly repellent to the idea of a free society that, as silly as it may sound, I'd be willing to fight to stop anyone from asserting that authority. Now... making the public pay increased insurance premiums or emergency hospital bills because I'm not willing to live a healthy life and can't afford to pay for it... that's an entirely different issue.
2 And here is where we follow up from that first footnote. There's the old adage, "your right to swing your fist ends at the tip of my nose." From the perspective of mandates, your right to live your life any way you want ends at my pocket book. That, of course, is the Conservative interpretation. The Liberal interpretation is that your right to live your life any way you want should be protected even if someone's pocket book must be dipped into. Oh, what an argument those last few sentences could start! But I hope you can see my point. What right does the federal government have to mandate what I eat? Well... if my choices cause other people some kind of distress (hitting their nose, so to say), then the government may have the right to restrict my choices. But what is distress? Should an obese person have the same rights to emergency medical care that a slender person has? If each is paying for it themselves, certainly. But what if neither can afford it? What if it's a life saving necessity? Who gets to draw the line? That, my friend, is the nature of diplomacy, politics, and society.