Actually a lot of people who follow a low-carb diet also count calories. Although, I think counting calories is over-the-top and completely unnecessary when you can easily stay under your daily calorie allowance by estimating portion sizes based on the size of your fist (equals roughly 1 cup) and reading nutrition labels.
I've used the My Plate
website to get an idea of the types of foods and how much of each food group I should be eating everyday to maintain my health and current weight.
As far as low-fat is concerned, I would stick to consuming low-fat dairy products only, because they're typically fortified with the same amount of nutrients as full-fat dairy. Other low-fat products (like meal replacements and junk food) contain less fat but usually have just as many calories and more sugar to make up for it.
You can also eat processed foods and still be healthy as long as you still strive to get all your essential nutrients from a variety of food sources besides processed foods. Reading nutrition labels is really what makes sorting the good stuff from the bad stuff easy. HTH