Anterior pelvic tilt is caused by tight hamstrings and weak posture muscles which are side effects of sitting all day. Weighted barbell squats fix this problem more effectively than anything else I know of. Walking is important, but a strong core is probably even more important for long term back health.
Doc here. Anterior pelvic tilt is a fancy way of saying "slouching". Slouching isn't bad. An Olympic squatter can slouch with the best of them. Slouching for 8 hours is bad. Stand. Walk. Just don't sit all day.
