There are several factors modifiable factors involved in building muscle mass and improving strength beyond weight lifting.  Total energy intake, meal and snack timing and nutrient intake all play important roles. 

Increase calories:

In order to build muscle, you need to eat more calories than you burn metabolically and through your exercise output.  Even if you eat enough protein, if you are under fueling, your body will begin to breakdown muscle for short term energy sources.

Determine your calorie needs with an on-line calculator using your height, weight, age, gender and activity level.  Use an on-line food log such as EAtracker or My Fitness Pal to keep track of your intake for a few days to see how much you are eating.

Aim to include more nutrient and calorie dense foods such as whole grains, dairy, legumes, nuts, seeds, lean meat and fruit and avoid filling up on low calorie or empty calorie foods.

Get Enough Protein:

Calculate your protein needs by taking your weight in pounds, divided by 2.2 and multiplied by your protein needs per Kg body weight.  If you are an average exerciser 3 times a week for 30-40 minutes your needs are 1g/kg.  If you are an endurance athlete, your needs are 1.6g/kg and if you are trying to gain muscle and weight you can be up at a maximum of 1.8-2.0g/kg.

Ex: for a 190lb man training for iron man who needs to increase muscle mass but not gain too much weight:  190 divided by 2.2=86.3 kg multiplied by 1.6g protein = 138g protein per day.

Space protein out throughout the day 30-40g at meals and 10-20g at snacks.

Protein content of sample foods:

1 cup milk = 8g protein

3/4c lentils= 13g

1/4c peanuts = 16g

2.5oz chicken = 20g

1 scoop protein powder= 25-30g (read the label)

BCCA (Branched Chain Amino Acids) such as leucine, isoleucine and valine help promote protein synthesis leading to muscle growth, especially for those not consuming enough protein.

Post-Workout aim to consume 20g protein within 40-90 minutes for maximum muscle building and tissue repair.  

Protein powders can be a quick and easy way to get protein after a workout.  Whey protein powders come from milk and soy protein powders are from soybeans.  There are also pea protein powders like those from Vega.  Add one scoop of whey protein powder to 1 cup chocolate milk with a frozen banana and ice for a quick protein rich smoothie snack.

Aim for balance:

Your body still needs carbohydrates for fuel and fibre as well as healthy fats for satiety and hormone production.  Aim for balanced meals including fruit and/or vegetables, whole grains for carbs, vegetable oils, nuts and seeds or avocado for fats, in addition to lean protein from meat, fish, poultry, legumes or tofu for protein. 

Prevent Muscle Breakdown:

There are several factors that can lead to muscle breakdown. 1. Not eating enough calories overall, 2. Not eating often enough so your body uses your muscle for fuel. 3. Not refueling during long endurance exercise lasting more than 60-90 minutes or not recovering with protein post workout for muscle and tissue repair.

Sample Recovery Snack Post- workout:

Quinoa bowl with toasted pistachios, edamame, avocado, mango, cilantro, bell pepper

Or

Frozen mango chunks, coconut water and Vega Protein+Greens.

Or

Whole grain toast with 2 Tbsp PB and a banana and cup of soymilk

Some people are genetically more adept at building muscle than others and there are of course differences between genders, however if you pay attention to the things you can change, you will be able to improve your own personal muscle mass, strength and power.