The entire amount of calories that we eat will have to come from the foods that we eat- throughout the day. Digestion of these foods will give us calories for our activities and we require at least about 1600 calories per day.
Let us now consider which food will give how many calories. Consider this- a north Indian person in Delhi eats paratha, bhature, chole, makai ki roti and so on; a Rajasthani eats bajri ki roti, puri, kachori, badi or sangri ki subjee; a Gujrati eats Thepla, dhokla, khakhra, kadi and pakora; a South Indian eats Idli, dosa, sambhar, idiappam, uttappam; a person in Manipur loves to eat noodles, Manchurian and fried rice. If we think of abroad- in the USA someone will eat hot dogs, burgers, pasta, ice creams; an Italian will have Pizza, Gratin; an Englishman will have toast cornflakes, pastry. If we consider all the people in every country and every dish they will love to have we may have about 10,000 dishes to calculate the calories. Endless charts can be prepared and books and tables can be made available to them so that they can calculate the calories. Further, if we calculate the variations in the contents of each of these recipes, it will only add to the confusion.
This is one of the reasons that common people and even the dieticians, doctors are confused about the exact calorie content of the food they eat. They lose track of whatever they have learnt in their colleges about calories. Many make gross mistakes in calculating calories and the charts are not always available.
Because of this simple reason people are not asked to calculate calories on their own and are given diet charts by the hospital dieticians. People adhere to this monotonous diet for some time and aftearwards, they eat outside the chart-and lose track of the calories.