The basic idea is to crave carbs only 3 times a day. I alternate my meals of protein, carbs and low fat with protein, fat & low carbs. The fats I use for the meals including them are mostly EFA's (essential fatty acids) such as flaxseed and sometime I will use monounsaturated fats like olive oil. By following such program it allows me to stay in 10-12% body fat level while simultaneously gaining lean muscle mass. The idea behind this kind of a program is to limit the insulin spikes caused by consuming carbohydrates. While insulin is very anabolic hormone it is a "storage hormone".
It drive much needed amino acids and glycogen into muscle cells, but it also has a tendency to deposit some of the calories into fat cells. By limiting the frequency of insulin spikes we can control the over all fat gain while trying to gain lean muscle mass. The example of such eating schedule would be:
Meal # 1 - Protein, carbs & low fat
Meal # 2 - Protein, fat & low carbs
Meal # 3 - Protein, carbs & low fat
Meal # 4 - Protein, fat & low carbs
Meal # 5 - Protein, carb & low fat
Meal # 6 - Protein, low carbs & low fat.
The first carb meal is great as we are just getting up from a long fast and we have the highest insulin sensitivity first thing in the morning. What that means is that our body needs to produce very little insulin to get the job done of transporting nutrients into appropriate places. I feel that most of the nutrients consumed at thins time will be absorbed very efficiently and not be stored as fat.
The second carb meal is consumed around lunch; as the insulin sensitivity is still high make the nutrient absorption still very efficient.
The third meal would ideally be right after your workout. As the insulin sensitivity is high again, we want to feed the body some simple sugars and protein to speed up the recovery as well as replace the used up glycogen from our workout.
The last meal of the day should be mostly protein; we do not want to go to bed with a lot of fat in our system as well as insulin caused by consumption of carbs. However we want to include some fats in the meals, as they will slow down the absorption rate of proteins, by that supporting positive nitrogen balance through out most of the night.
The use of flaxseed oils will keep your overall calories high enough to cause lean muscle tissue growth, and the flaxseed oil contains EFA (essential fatty acids), which are responsible for maintenance of healthy metabolism, hormone production as well as nice smooth skin and healthy hair etc.
I find this system works very well for me, I can usually gain about 1 pound every week or two and I am pretty certain that most if not all of that is lean muscle mass. Remember though it is the off season for most of us, so enjoy the festive foods and have some snacks as this is the best part of the year to indulge in some good tasting foods. If you have most of meals as planed a couple of cheat ones will not make or break your progress. As one guy I know said; "If I eat 42 meals a week and 40 of them are perfectly balanced and health, it is not going to make a difference what I eat the other 2 meals, no matter where they come from and what they consist of". So with that thought go and grab yourself a snack.
Here is an example of the diet I follow when trying to gain lean muscle mass, this will give you some ideas of food combinations as well as what an actual diet like this might look like. You will notice I eat 7 meals a day, but eating 6 meals as outlined above would be fine as well.