Those are great for individual impacts. Not perfect solutions, but they would definitely reduce personal risks.
At the population level though, they'll do nothing to slow the spread of COVID. If the entire country was the perfect weight, super fit, only consumed the perfect diet, with no high sugar or high inflammation foods, they would still all get sick eventually. Those perfectly fit people would all continue to spread COVID on to other people. If that's all we did without any vaccination at all, individual impacts might be better on a percentage basis, but the ultimate number that got sick would be so much larger that even the lower percentages of bad outcomes would be a larger absolute number of bad outcomes.
I'm all for individuals doing things to make their personal outcomes better. But, we cannot stop there. We have to do the things that also make the population outcome better. It's nice that they line up. The best thing someone can do to improve their personal outcome is also the best thing they can do to improve the population outcome.
Everything else is doing something that's not the best for each individual, just something better than nothing.