@AmyG1982 while I do not know my resting heart rate before going low carb/keto 5 years ago my current resting heart rate is typically in the 50-60 range. Some literature indicates a heart burning ketones vs glucose can be up to 25% more efficient. I expect the vaso dilatation effect of ketones are a factor as well.

Below is from a top ketone scientist that I have found helpful over the years. This happens to be a podcast but he has professional research papers on this subject on the web.

https://fxmedicine.com.au/content/ketones-fourth-macronutrient-dr-dominic-dagostino#2531

"Dominic: Yeah. And you know Richard Veech, I mentioned him, the student of Hans Krebs, did work back in...I think it was published about 20 years ago showing the hydraulic efficiency of the heart is about 25% greater when your heart is burning ketones, relative to glucose. So, this was a profound change. And especially since, with ketones, you don't need insulin, that you can actually generate ATP without the presence of insulin. So, ketones are very good for the heart. The heart burns fatty acids really well, it burns ketones really well.

And the brain, some argue the brain functions more efficiently off ketones than it does with the glucose. We do know the ageing brain gradually uses glucose less efficiently. You know, even in a healthy individual, the glucose metabolism in the brain will decrease with ageing, and that's not the case with ketones. The ability of the ageing brain to use ketones does not decline with age. And this is work by Stephen Cunnane in Canada who's shown this doing a dual PET scan. So that's some pretty exciting work basically demonstrating that ketones could help maybe restore brain energy metabolism, you know, that's associated with cognitive decline with ageing."

Dunno, I seem to have kept the same heart rate throughout my adult years. Generally 60 resting. Didn't matter when I was overweight, or at my lowest, eating higher healthy carbs or low carbing, working as a fitness trainer or totally sedentary when I first became ill with an autoimmune disease. I do know low heart rates run in my family (Dad's side) the guys are very low with heart rates around 45-50. Gals - closer to mine. You may just be getting a stronger healthier heart.

mine has actually gotten slowly higher than normal, am in mid 80’s nowadays instead of the lower 70’s that i was regularly at before my carbs went under 20 netcarbs for good. i’ve constantly gone way over on my saturated fats and my cholesterol intake in last 2 1/2 months so guessing maybe why. it is still under the normal 100 range though and i’m sure being less active since being stuck at home doesn’t help any so am not too worried.. now my blood pressure and blood sugar on the other-hand have gotten way low since i went into ketosis!!