Gaining 15 lbs. of muscle mass is a daunting challenge specially if you want to stay lean enough to display your 6 pack abs. Typically, gaining mass requires eating more calories, which in turn can end up being stored as body fat. Your individual metabolism is the best guide to how much you should increase your calories to achieve muscle gains, while keeping your abdominal muscles visible. In his "Size Surge" experiment, author and Ironman Magazine contributor Jonathan Lawson was able to gain 20 lbs. of muscle while losing body fat. This feat was performed over 10 weeks without the use of anabolic steroids. Follow his lead to gain 15 lbs. of muscle and keep your abs.
Use nutrient timing to maximize muscle-building, while minimizing fat storage. For example, consume most of your "clean," low-glycemic carbohydrates in the earlier part of the day, more specifically, stacked around your weight-training workout. Drink a post-workout shake containing 50g of whey protein, 100g of high-glycemic carbs and 30g of healthy fats (flaxseed oil or medium-chain fats). According to the "Muscle Nerd" Jeff Anderson, this nutrient-timing strategy can help accelerate muscle gains.
Limit carbohydrate intake in the evening, especially high-glycemic starches and sugars. Since carbohydrates are our bodies' primary, preferred source of fuel, we should not need many of them prior to going to bed. Instead, focus on consuming lean proteins such as fish, chicken, pork or turkey and healthy fats such as avocado, olive oil or nuts. Take a protein shake with 1 or 2 tbsp. flaxseed oil immediately before going to bed to improve muscle recovery.
Perform three full body workouts per week. Use compound movements that engage a large amount of muscle fibers, such as squats for the legs or bench press for the chest muscles. Squats and deadlifts in particular trigger the body to produce testosterone and growth hormone, which are essential to muscle growth. By using a repetition range of nine to 12 reps on each exercise, you can focus on muscle growth.
Do 10 to 30 minutes of "super cardio" immediately following your weight-training to ensure that fatty acids released for energy are burned rather than restored. This is Jeff Anderson's name for low-intensity cardio following resistance-training. Since you have burned most of your glycogen (muscle-stored carbohydrates) during your workout, your body will use primarily fat for energy. Examples of low-intensity cardio are steady-state walking on the treadmill, riding the exercise bike or using the elliptical machine. This will help ensure that you keep your abs while gaining muscle mass.
Always get seven to eight hours of restful sleep per night. Our bodies do not grow muscle in the gym. Muscle is built while we are resting and sleeping. Moreover, important hormones for muscle growth and fat-burning are also produced while we sleep. Irregular sleep patterns will quickly lead to over-training and failure to achieve your goals.