You gave me something new to try. Never had kefir, but just read about it and I’ll look for it - sounds interesting.
Kefir is like sour cream or yogurt, a little on the sour side. I sometimes mix it with half and half. Fat doesn’t stick to me yet. (Besides, fat is necessary!)
For probiotic, you may be better off with kimchi or sauerkraut. They say dairy probiotics are often dead on arrival in the gut, destroyed by stomach acid. Cabbage doesn’t have that problem.
More important, avoid sugar, limit grains, and increase the vegetable intake.