Calories are the wrong thing to be looking at.
Simple physics tells us that if you take in less calories than you burn you lose weight. The thing is hardly anyone will succeed in maintaining this. Once the calorie controlled diet stops, fat is put on quickly and probably muscles have deteriorated during the calorie controlled diet.
A lifestyle change is the only way that you will lose weight permanently. And even then many people think they want to lose weight but in fact what they want is a different body shape – which may be lighter or the same weight.
If you look at the calories burned during exercise it is insufficient to account for real weight loss that is seen cumulatively. When you change your lifestyle (with more exercise) then the after-exercise effect of increased metabolic rate kicks in for the whole day and longer. Half an hour of sweating leads to lots of calories lost.
Calorie controlled diets are for weak minded people who can’t and won’t lose weight (in most cases)
via Anthony Garcia’s Train Hard and Expect Success Blog