I believe the 1918 flu also had the unusual property of killing people in their 20s at a higher rate than the middle aged and old. https://wwwnc.cdc.gov/eid/article/12/1/05-0979-f3

For much of 1918, a lot of people in their 20s getting the flu were also experiencing trench warfare, which can't be an optimal situation, both in terms of immediate self-care and co-occurring health conditions.

Older people were less vulnerable in the U.S. as well. The problem was that young healthy people were more likely to have an immune system overreaction. This applied to both genders.

(Source: John Barry's The Great Influenza)

I guess you should see that it was just men in their 20s in the stats then?

Ha, fair enough! I made sure to word that carefully...

But in general, good health leads to better outcomes, and we know that's the case with covid.

Totally anecdotal but Prodigy of mobb deep had sickle cell and he said many times eating healthier, working out, etc. had a positive impact.