Lo fat, often means hi sugar content. is it best when comparing foods to just focus on calories. or does it depend what the health issue is?

Yes, it depends, but: Yes, low fat means high carbs. While some believe all calories are equal, good research suggests that a high carb/high starch diet increases weight more than a high fat/low carb diet due to how carbs affect metabolism. Emphasize healthy fats & healthy carbs (complex vs. Simple). For an interesting article on this see http://www.Nytimes.Com/2012/07/01/opinion/sunday/what-really-makes-us-fat.Html.