Yogurt is healthy food unless it's commercially sweetened. The flavored yogurts sold in grocery stores are sweetened for kids. A typical 6-ounce serving contains as much as 25 grams (6 teaspoons) of added sugar. Glycemic loads range around 110. If you add your own fresh fruit to plain yogurt, you'll find that it tastes great with no added sugar or maybe a single teaspoon, which would have negligible effect on the glyemic load. Don't bother with low-fat yogurt. Just get the no-sugar-added kind.