50P/30C/20F is pretty much what I cut on, and I have the same inactive type of job. I found I feel satiated during the day by avoiding carbs when sitting on my ass. So I'll have half my carbs with breakfast, which means it's pretty flexible. Then I'll have a protein shake and a container of nuts to snack on while at work. So my lunch is pretty small. Then a small carb meal before training (rice cakes), and the rest of my carbs with dinner.
It's just a trick that works for me, but ultimately weight loss will come down to your overall caloric intake.
One thing you'll notice when tracking calories is all the snacks/coffees high in calories you weren't really paying attention to. Taking those out of your diet will have a big impact.