Building Lean Muscle, Part 2: Constructing the Right Diet

This is the second installment of a 10-part series on how to build lean muscle (get caught up with Part 1). If you’re looking for the best way to put on muscle—in addition to training on a proper strength program—you have to take a good hard look at your diet.

Athletes who take the time to learn how to eat right will almost always have greater success in terms of building muscle quickly and safely. I can’t tell you how many clients I see wasting time going around in circles because they aren’t eating enough calories to support new muscle growth—or, conversely, athletes who are eating more than they need and gain fat along with muscle.

Food can make or break your results. If you don’t provide the body with the right amount of raw materials for growth, how do you expect it to generate more lean muscle mass?

Answer: it won't.

Here are 3 key steps to remember as you construct your muscle-building diet, so you can succeed in achieving safe weight gain.


The first thing you will need to do is determine your body composition—i.e., what percentage of your body weight is made up of lean muscle vs. adipose tissue (fat). Knowing your lean body mass is going to make figuring out your daily calorie requirements much more accurate, since fat mass burns so few calories at rest.

Athletes who are quite lean to start with will have higher caloric needs and must adjust their diet to put on muscle accordingly, otherwise they might not reach a high enough calorie intake to actually gain size.

There are several methods for measuring your body fat percentage. If you have access to a coach or someone trained to use hand-held skin calipers, this is an accurate low-cost, low-tech method. You can also use an online body fat calculator that uses body circumference measurements to estimate your body fat percentage (this method is not the most accurate). Bio-electrical impedance devices measure body fat based on the time it takes a current of electricity to navigate through the tissues of the body, but results can be compromised by athlete hydration levels and the presence of food in the stomach.

Finally, if you don’t mind spending around $50, you can get your body composition measured using hydrostatic (underwater) testing. Hydrostatic testing, sometimes called "dunk tank" testing, measures the differential between your mass on land and your mass underwater, and give an accurate assessment of body fat vs. lean tissue. Retakes are usually cheaper—around $30.

Whichever method you choose, stick with it for your preliminary and follow-up measurements. So, if you get measured with calipers first, make sure you use calipers to measure your composition as you progress in your goal to gain muscle to make sure your results are consistent.



Once you have determined your body fat percentage, the next step in figuring out your muscle-building diet is to establish your daily calorie expenditure: the amount of calories your body uses on average per day. Once you know your caloric expenditure, you can make sure to eat not only enough to sustain your daily activities, but enough extra to accommodate the growth of lean muscle tissue.

To estimate your daily expenditure, you will use the following formula:

BMR (Basal Metabolic Rate) = 370 + (21.6 x lean mass in kg)

This number will represent how many calories you’d burn each day if you did literally nothing but lie in bed. It accounts for all the basic physiological processes required to keep your body alive. So, if your total lean body mass is 150 lbs or 68 kg, your BMR = 370 + (21.6 x 68) = 370 + 1468.8 = 1,838.8 calories per day. Meaning, if you sit on the couch all day watching every episode of Parks and Rec on Netflix, you’ll burn around 1,800 calories doing it.

But now we need to account for the actual activity you do on a daily basis. Take the number above and use one of the multipliers below to get an accurate estimate of your actual daily burn:

If you are sedentary (little or no exercise) = BMR x 1.2

If you are lightly active (light exercise/sports 1-3 days/week) = BMR x 1.375

If you are moderately active (moderate exercise/sports 3-5 days/week) = BMR x 1.55

If you are very active (hard exercise/sports 6-7 days a week) = BMR x 1.725

If you are extra active (very hard exercise/sports & physical job or 2x training) = BMR x 1.9

Most of you will fall in the range of moderately active to extra active depending on just how frequently you’re training and exercising, as well as how your daily life stacks up in terms of activity. Using our example above, an athlete with 150 lbs of lean muscle mass  and is moderately active would multiply 1,838.8 x 1.55 = about 2,850 calories per day. This is the number of calories this athlete must consume per day in order to maintain their current body composition.

If you are looking to gain muscle mass, you will need to eat more than your maintenance calorie intake—a calorie surplus. Ideally, you should add between 250-500 extra calories per day to your maintenance intake number. This will result in 0.5-1 lb of weight gain per week, and will help you stay lean as you build muscle. Any surplus greater than 500 calories can create additional fat mass, which is not productive to your goals.


OK, so now you know your BMR, your maintenance calorie intake, and the surplus you will need to build muscle. Once we’ve arrived at this figure, we also need to factor in bioenergetics—which energy system your body uses as you perform your chosen sport.

Sports like football and track and field (sprinting) will rely heavily on the immediate (phosphagen) energy system and anaerobic glycolysis as mechanisms for creating the energy molecule ATP. These energy pathways enable the body to produce high levels of energy very quickly, but they fatigue just as fast.

Sports like basketball, soccer, and hockey rely more on anaerobic glycolysis, shifting to oxidative glycolysis as the demands of these sports require more endurance.

Finally, true endurance sports like cross-country running or skiing rely most heavily on the oxidative system, which delivers energy at a lower intensity level for a longer period of time.

Knowing which energy pathway your sport relies on will affect the composition of your diet in terms of macronutrients. The more glycolytic the nature of your sport, the more carbohydrates you’ll need in your diet to fuel that need for fast energy. The more oxidative your sport, the more dietary fat you can consume and still maintain energy. Athletes who participate in very long-distance sports may also require more calories overall, simply because they are burning to many in each workout.


These are the first 3 important steps in constructing a good diet for building muscle, but this is really only a general overview of what to eat to gain muscle. Next time, I will dive a little deeper into the specifics of that diet to learn more about the right kinds of carbohydrates, proteins, and fats, as well as macronutrient ratios, to help you fill in this outline of your diet.


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Mike Bewley, MA, CSCS, C-SPN, USAW-I is a guest contributor to the Volt blog. He is a Strength and Conditioning Coach at Clemson University, a specalist in sports nutrition, and the founder of online nutrition platform NutraCarina.