The carbs in SF fiber supplements are all fiber, won’t interfere with weight loss. Since switching back to counting net carbs (where I started with the New Atkins for a New You) I no longer need supplements…I eat more vegetables with fiber and minerals.
I did use magnesium when I was VLC, taking one capsule at night or used the Natural Calm drink. Dr Westman recommends a small amount (a teaspoon) of Milk of Magnesia daily, if constipation is a problem.