Kefir is kefir and yogurt is yogurt. They are two different things.

I look at it this way: Water is being drained from the yogurt but the milk solids are left behind. It's somewhat like making cheese where the milk is curded and removed from the water.

I doubt that the milk sugars are draining off as they're an integral part of the milk.

If that is true, there would be more carbs in the same amount of yogurt cheese - more everything actually - because the water has drained out and the product has become more compact.

Karen