Can walking for 7-8 km a day help in weight loss?

Yes.

I will add the most efficient way to walk to get the most value from your time.

Fasted walking.

Best time: Right after waking up (drinking a liter of water.)

Why: Cortisol is at its peak right when waking up, and you are in a fasted state after waking up (six hours of sleep or more). Cortisol is catabolic; it breaks down fat among other things.

Also, walking fasted raises human growth hormone, which burns fat and preserves muscle mass.

So, you get a double-edged sword of greatness with peak cortisol levels and boosted growth hormone if you walked in a fasted state right when you wake up.

Of course, if you eat anything you will spike insulin which is anabolic (makes fat grow.) — Moreover, eating also breaks the sword of greatness by abolishing both human growth hormone & cortisol output.

You walk 7–8km every day as you say; it would be just like you saving up 10–15% of your income every month into a compound interest bearing accounting.— The fat loss results would start to pile up for you.

Simpy put, the more you walk fasted, the more lean mass you will preserve while burning fat.