If you are new to dieting, every article you have read on the subject has probably mentioned “calories,” but without much of an explanation of what calories actually are. Once you understand calories and how they work, you will be better able to distinguish between unrealistic weight-loss systems and the ones that really work.
Every daily activity, from exercise to digestion to simple breathing, requires energy. This energy comes from the food we eat in the form of calories (the definition of a calorie is the amount of energy it takes to raise the temperature of water by one degree).
When you consume calories, two things happen: Some of the calories you eat will be tapped by the body as an immediate source of ready energy, particularly if you are exercising. The rest of the calories you consume will be stored away as body fat to be drawn on for energy in the future.
As long as you are eating a healthy diet, your body will not end up with excess stored fat, but if you are not following a healthy diet or overeating, your body will store more energy as fat than it can possibly use in between meals.
In order to reverse the fat-storage “vicious cycle,” you need to create what is known as a “caloric deficit” – this simply means that you must eat fewer calories than your body burns as fuel in a day, forcing your body to draw on stored body fat for extra energy.
As far as the way your body responds to a caloric deficit is concerned, the source of the calories does not really matter – you could, in theory, lose some weight eating only french fries, as long as the calories added up to less than your body needed.
Figuring out how many calories to cut and how many to keep, however, can be a tricky balance: If you do not cut enough, your body will not have to burn fat for energy. On the other hand, if you cut too much, your metabolism will go into “starvation mode” and your body will begin storing more calories as fat, making your diet worthless. For maximum results, you want to maintain just a slight deficit that will make your body burn fat but avoid slowing down your metabolism.
Generally, you should aim to consume about 300 to 500 fewer calories than your body’s daily caloric needs, which can be accomplished fairly easily just by cutting portions slightly at each meal and avoiding sources of empty calories like soda.