There are various ranges given for men and women. However, each individual is so unique that standard calorific requirements do not fit everyone. There are healthy and fit adults who thrive on even 1000 calories a day and some require 2500 calories.
Further, calorie requirements change even in an individual based on age, lifestyle changes, season and type of work. These changes are not small and the body cannot adjust to the same intake at all times. Even within a given year, your requirement varies.
If there is anyone who claims to make you slim or fat or well built purely based on diets alone is probably pushing a fad diet on you. Such diet plans may show results in the short term but create long term internal changes and deficits which are not good from a health point of view. Weight management and body improvement can happen only by making lifestyle changes along with a proper diet. A nutritionally balanced diet at all points of time is the key to a healthier life.
Diet is about leading a healthy lifestyle. If your health indicators are good and you have a balanced life, you need not worry about your body. Each person has a different body structure. You could be on the thinner side, chubbier side or built side. This is determined by genetics. If you try to go against that to get a perfect body, you can do long term damage to yourself.
It is a diet schedule which takes into account your lifestyle, work schedules and food preferences. You need to have customized diets for your needs.