As someone whose weight has been all over the place in my life, I really appreciate hearing this. I've known it is true forever, but it is rare to hear other people saying it. There is much more to weight than calories in/out. Some people can skip a meal without noticing, others count the minutes until the next meal. I always flip it on its head. For some reason it is easy for people to understand that certain people would have trouble gaining 20 pounds, others could do it in a month easily. But when you talk about losing 20 pounds, people start talking about willpower.