Done that myself a few times. In the present system, those who aren't able to walk, don't have to, and those that can, ought to be encouraged to, for the matter of public heath.
That short escalator ride isn't a public health disaster.
The lack of healthy food available to commuters is probably a bigger problem.
Recall how much the idea of evolution bothers some people. Are you sure this isn't a similar type of situation?
We seem to have evidence that obesity isn't always a choice.