Imagine you and a friend are trying to lose weight, and are given a daily allowance of calories, say 1,800 per day. You choose to eat vegetables, whole grains, lean meats etc. in that amount. Your friend instead chooses to eat burgers, colas, cookies and so on. Who do you think would fare better after 30 days?
Counting calories by themselves is not a guaranteed path to weight loss. You also need to take care of where the calories that you are taking in are coming from. You should aim to have a complete, balanced daily intake, with calories coming from fats, carbohydrates and proteins. Aim for healthy foods that are rich in vitamins, minerals, fibre and other key nutrients. In this way, your body will have energy to get through the day and store only what is necessary.
On the other hand, when you are taking a lot of calories that come from sugar, your insulin levels will spike, and all the excess sugar is turned into fat. 500 healthy calories, coming from foods such as vegetables and whole grains, will have a completely different impact on your body from 500 calories coming from a bar of chocolate or a Big Mac.
Even though keeping track of calories is an important part of any weight loss programme, always keep the whole picture in mind; your aim is not only to lose weight, but to live a healthy, balanced life. A good, nutritionally balanced diet is one of the cornerstones of that life.