Any negative effects from being on a low carb diet?

I’ve followed Dr. B in some form since 2006. I would point out two concerns. One is the suggestion that low carb over time will result in a downregulation of your thyroid. But I’ve never observed this downregulation myself. The other issue is exercise performance and in particular the ability to get nutrition to recover from exercise. One of the things I had found over the last two years is that I had basically “stalled” in my weightlifting performance. Since starting insulin and specifically eating carbs before and after workouts, I’ve broken through some of those stalls and made progress.