I wonder if this has helped me in the past. I am on a weight loss stretch again now and hope it has a positive effect (going towards normal weight probably does! - I am 20 lbs. away)
I can tell from my Oura ring that my heart rate and heart rate variability overnight were super-improved when I lost 26 pounds in 2024. Better sleep at night, fewer symptoms. I have to specify: this was during the time of calorie restriction. Even though I am lighter now, the positive effect is gone.
Not everyone needs to lose weight (some of us are too thin) but those of us with a few extra pounds, it may be worth a try.
Be careful not to fast for more than 24 hours (a healthy person's safe limit, I think, because of electrolytes and such) and less, if you have medical issues - but eating less and being on a calorie deficit may still be doable for most to try to see if it helps.