Ghee/clarified butter is pretty much pure butterfat -- butter minus the trace amounts of water, protein, and lactose. It is pretty expensive though...

I've been making homemade yogurt from lactose-free whole milk because it seemed like the store-bought yogurt had too much lactose. Note that the lactose-free yogurt still has sugar in it, just simpler sugars than lactose which are more likely to be quickly digested instead of fermenting in the gut -- so you'd have to count those sugars towards your daily sugar limit. The upside would be that yogurt is a probiotic.