One of the main points of Good Calories, Bad Calories is that calorie intake isn't as important as what type of calories you are consuming in how overweight and healthy you are.
For example: they did a test where people consumed 800 calories per day, 400 in protein, 400 in fat. These people were NOT hungry. Then they added 400 calories of carbohydrates. They became famished.
They also tried forcing people to overeat protein and fat, and couldn't. Then they did the same with carbs, and people were eating upwards of 7000 calories a day and were still hungry.
Non-fat or low-fat stuff is bad. They basically removed the fat by processes you don't want to know about, which makes things untasty. So to add tasty back, they put in either sugars, which spike your insulin, which leads to weight problems and diabetes. Or they use high fructose corn syrup, or just plain fructose,
which is basically alcohol without the high, so really bad for you. In the early 1900s, we would have maybe 15g of sugar per day, from a variety of sources. This one little lowfat yoghurt next to me has 19g of sugar, plus 3 or 4g of assorted non-fiber carbs. Don't even look at a bottle of soda...
I've stopped caring about calories. I make sure I avoid simple carbs (e.g. sugar), basically. Those are naturally replaced by fats, proteins and complex carbs with lots of fiber. Trying to almost quit sugar altogether - fructose is evil. Also, avoid buying things whose ingredient list is a wall of text.