Heart rate is dropping

Hello all. This is my first post here.

About a month ago, my doctor told me to adjust my diet because I was either diabetic or pre-diabetic (tbd). I have a follow up next week but I noticed a strange trend and wanted to ask.

Prior to changing my diet, I had noticed that my heartrate was creeping up (high 70s/low 80s resting). With just a little activity, it would jump to 105-110 but nothing crazy. Once I cut carbs on my diet, my resting heart rate has fallen into the 60s. I am currently eating between 150-200 g of carbs per day and a 2000-2300 calorie diet (5'9'', was 278 but now 260). Has anybody else experienced something like this initially on diet change?

Thank you!