The simple key to successful weight loss programs is to burn more calories than you eat. There are a lot of myths about negative calories and various magic potions and guides for losing weight that are mumbo jumbo. The secret for losing weight is simple - you need to eat less food and fewer calories each day for the rest of your life. Exercising more, and changing your lifestyle helps as well as you will burn more calories. If you consume less calories than you burn through exercise and your generally metabolism at rest you will lose weight. This is called a calorie deficit. If you add up the calories you eat and subtract the calories burnt in your generally metabolism at rest and via exercise you get an estimate of your calorie balance. If it is negative - that is you burn more calories than you consume in food you have a calorie deficit. Your body has to break down fat or protein to make up the difference. This means that you will lose weight over time. If your daily calorie balance is positive your body will produce more fat and store it somewhere.
Recent research has confirmed that there is a set-point weight for each person. The body has a built-in response to starvation or calorie reduction. The resting metabolic rate is slowed. This means that when you diet it gets harder to create and maintain a calorie deficit so that you lose weight and keep it off.
Many people who lose weight through dieting quickly put the weight back on when they resume their normal diet and eating patterns. Successful weight loss requires major permanent changes to lifestyles including meal and portion sizes, diets and exercise routines. Monitoring your calories and keeping a calorie deficit or a near zero calorie balance will ensure you do not put the weight you lose back on when you stop dieting.
This site has a number of tools to help you understand, monitor and track your calorie deficit:
Up to date Articles about Calorie Deficit and effective weight Loss
Calorie Deficit WebApp - This simply tool helps you to check whether you have a calorie deficit each day. There are male and female versions using pounds and kilograms for body weight. You enter your height and weight and the tool calculates the number of calories you burn at rest (resting metabolic rate). You then enter the calories you eat in food and burn through exercise. The tool then calculates your bet calorie balance for the day.