That's what I've always thought about it as well. My wife and I have always been physically active, and our diet (and consequently our childrens) is about 80% wholefood. None of us have had covid (that we know of, of course. We have randomly tested just for interest sake, or going on/returning from holiday abroad).A lot, I would say. Physical exercise, diet and good overall health is directly linked to your immune system and fending off such viruses.
I'm of the opinion* that the effect of covid on a person is directly affected by their existing physical condition. Ergo, the heathier you are the better your immune system is at fighting infection of any kind.
*my opinion is based on nothing more than my own thoughts and experiences. I am not a medical or scientific professional