While there is some truth in the calorie principle, it dismisses the fact that different types of calories are burned differently within our bodies. While fat is often singled out for attention in low-calorie approaches, there is evidence that when calorie intakes are the same, individuals that eat the most fat actually lose the most weight.

Also, the effect the food you eat now has on your appetite later will also determine, ultimately, its influence on food intake and weight.  For example, if you are eating fiber rich foods opposed to munching down a bags of chips.  The key to long-term weight loss is not to concentrate on the quantity of the food that you consume, but its quality.