People who eat 40% of daily calories from protein lose more body fat than those whose diets have only 15% protein, even though they consume the same number of calories.  A calorie is a calorie, but your body burns about 25 to 30 of them while digesting 100 calories of protein versus only 7 of them  while digesting 100 calories of simple carbs, i.e., table sugar. 

So don't forget to eat your meat!