The number of ‘net’ calories a person needs to consume depends on a number of factors such as their age (are they developing as an adolescent for example), their activity level, their fitness goals etc. As with anything in our industry of fitness, there is no one size fits all answer to this question. One of the key attributes of a good trainer is to explore the details that are important to the specific client and then adjust our answer to THAT PERSON. I would highly recommend when it comes to dietary assistance that any trainer work with or refer to a registered dietitian.
I hope that this helps.