This is fine in a warm country, or in a place where you're going to be in or out of your house all the time. Living in a cold and/or isolated place, being cooped up in such a small area would be unhealthy, you need to move around much more as a matter of course. Particularly if you're working at home, you'd have to be very proactive to avoid serious impacts on your health, because your lifestyle would be almost inherently sedentary. Exercise is not just doing a certain amount of cardio each week, you have to have movement interspersed throughout the day.

I reckon you could have various different 'pods', though, rather than a standard house. A small space like this, then an isolated office room five minutes walk away, perhaps a cafe/communal eating area somewhere else ,and so on.