You're making several errors, the first of which is that it's overweight people whining about BMI. It is not, from what I've seen. Fit people talk about BMI. I was one of them, and I was borderline overweight despite being a very thin person.
The second is that one's daily schedule is irrelevant if they are careful about what they eat. A full meal can be very low in calories, and a lack of exercise does not necessarily lead to obesity. There are many, many more factors at work here.