Mike, I wouldn't worry about the exercise too much at this stage. Unless you're a serious professional athlete, active exercise generally only makes up a tiny proportion of Total Daily Energy Expenditure (TDEE). I know that the vast majority of my own weight loss came from the low carb diet and not the walking to work, because I started my walking six months earlier, and it hardly made a difference on its own at all.

It's also worth knowing that there is evidence out there to suggest that a low carb diet can actually speed up one's metabolism. This study by David Ludwig's team demonstrates passive benefits of up to a couple of hundred extra calories burned per day, purely by virtue of reduced carbs in the diet.

So yeah, there's plenty of benefit to be gained from the diet alone. I'd let the exercise take care of itself. If you're anything like me, you'll start moving more once it starts to feel easier for you to be moving more.