Stop doing what doesn't work.

For 16 years you've walked the same walking route at the same time every morning, usually with the very same person. 6 kilometres, every morning, yet still you're overweight... What does that tell you?

It's not working. 

Your body has got used to that amount of exercise and has made the adjustments internally to accommodate the same amount of energy you burn each morning. 

From where I am standing, you have two options. Continue to do the same, and continue to get the same results or change to something else that works. 

Ride a bike, buy some hand weights, skip, jog a little, walk another route in the evening instead, visit a gym, see a PT who really does have your best interests at heart, go for a swim. Anything that gives your body something else to think about. It does not have to be difficult nor cost a lot of money. 

Same results or different?

You choose.