Quite simply, the main principle leading to weight loss is the one which says that one needs to burn more calories than he, or she, consumes. Losing calories is essential if you are intending to shift those pounds. This is because the energy in your body comes from the number of calories that you consume and, for the average person, you need 1900 to 2400 calories per day to be able to sustain your weight (for females and males respectively). This is because that is the average number of calories that you are likely to burn off during the average day.
If you consume more calories than this, then your body has, in effect, an excess of energy. When you have energy in your body, that is not used, it is converted and stored as ATP in your body; essentially as fat. This is why you put on weight (likewise, when you exercise you burn more calories off, than you consume, so your metabolism converts this ATP back into energy which is then used).
Therefore, losing weight is as simple as that; eat more calories than you use and you will gain weight, burn more calories off than you take in and you will lose weight.
The issue is that all food we eat makes us consume calories. It is the nature of food that it contains energy that we then use (otherwise why else would we eat?). Calorie counting is relatively straightforward as it only relies you keeping track of the food that you are eating and is, therefore, easy to incorporate into a food diary. Whenever you eat some food, note down your calorie intake from it and keep a running total so that you know how many you have consumed throughout the day. Then, when you have consumed your optimum number of calories, stop eating! It’s as simple as that.
Essentially it means that you can eat whatever you want, whenever you want just as long as you don’t exceed your daily limit (this is similar to Paul McKenna’s philosophy of eating what you want, when you want and stopping when you’re full). There are numerous websites that allow you to calculate your calorie intake if you don’t want to do the arithmetic.
What is also important about calorie counting is that you are able to spot patterns in your eating that perhaps contribute to your weight gain; you can identify which foods are leading you to consume more calories and you can then search for an alternative. Similarly, you can work out how much more exercise you need to do during the day in order to burn calories off. All in all, if done correctly, calorie counting can be incredibly effective at helping you to lose weight.