There is no need to keep adding fat back to the food. If you are doing the diet properly, you will get plenty of fat from what you are eating. Anyway, the extra fat is really only beneficial in the induction statge to bring on ketosis.
Atkins said that using lean cuts of meat are appropriate at all levels of the diet. he wouldn't have said that if he expected us to keep dumping fat back over top of the food. he also said that butter and cream sauces should be occasional treats not a daily part of your eating plan.
There is a sticky on the inductionforum which discusses this:
(How much fat do I need to eat?)How much fat do I need to eat? - Atkins Diet
Keep in mind that while fats don't add to the carbs they do add up in calories. I am not advocating a low fat diet, but as written, this diet has plenty on its own.