In order to increase your lean body mass, you might have to include a few things in your diet plan that you are not really going to enjoy.
Some of these are:
1. Hard boiled eggs
2. Fatless boiled chicken
3. Fatless fish
4. Protein shakes
5. Whey protein: This should be consumed after workouts.
It will help put the proteins back into your muscles faster than any other proteins. All these snacks might not satisfy your taste buds but remember that your purpose at the moment is to get increase your lean body mass. Foods without spices will help you since spices are rich in sodium which will result in increased water weight.