Eating for Gaining Lean Muscle Mass, Part I

I want to gain lean muscle mass and lose body fat.

I go to the gym and lift heavy weight to give my body a reason to build bigger, stronger muscles. I want to give my body the fuel to train hard and the building bricks to grow. I do that by eating good food, and enough of it.

How do I know if I eat enough?

I start by calculating my BMR, Basal Metabolic Rate, the calories my body needs at total rest. You can calculate it with the Harris & Benedict equation, the Mifflin-St Jeor equation, or the Katch-McArdle formula.

Mifflin-St Jeor:
  Men:   BMR = 10W + 6.25H − 5A + 5
  Women: BMR = 10W + 6.25H − 5A − 161

Revised Harris-Benedict:
  Men:   BMR = 13.397W + 4.799H − 5.677A + 88.362
  Women: BMR = 9.247W + 3.098H − 4.330A + 447.593

Katch-McArdle:
  BMR = 370 + 21.6 × (1 − F) × W

  W = body weight (kg)
  H = body height (cm)
  A = age
  F = body fat (as a decimal)

A normal BMR is roughly 1600–2600 calories for a man and 1400–2200 for a woman. You can also do a Bod Pod body composition measurement, which gives you a BMR figure too.

Because I'm not at total rest all day, I work out my daily calorie need by multiplying BMR by an activity factor from 1 to 2+.

• 1.0–1.2: Near-total inactivity. Practically never used unless you're ill.
• 1.3–1.4: Drive to work, lunch out, home in the evening. A relatively uneventful day.
• 1.4–1.6: A long walk, or some cleaning, washing and shopping.
• 1.6–1.8: A hard gym session, or a couple of hours of physical activity plus errands. Moving a lot, but nothing extreme.
• 1.8–2.0: A hard gym session plus cardio, or a hard cardio workout, or lots of everyday movement.
• 2.0+: Hard training (cardio burns more than strength work) combined with plenty of everyday activity.

Now I have my calorie need including daily activity. A normal range is roughly 2200–5000 calories for a man and 1800–4000 for a woman.

Protein requirements

For average gym-goers, 1.4–2.2 grams of protein per kilo of lean body mass is recommended. People training hard at a higher level may want more, up to 3–5 grams per kilo of lean body mass. So I multiply my lean body weight by a factor of 1.4–5 to find my daily protein need.

One gram of protein is 4 calories, so I multiply my daily protein need by 4 to get its calorie amount, then subtract that from my daily calorie total. What's left is for carbs and fat. Carbs are 4 calories per gram, fat is 9. I aim for roughly 50% of my calories from protein, 25% from carbs and 25% from fat.

From there, a calorie-counting app on my phone lets me log my food and check that I'm hitting the right amounts of calories, protein, carbs and fat.

Building muscle vs. losing fat

To gain muscle, I add 200–500 calories on top of my calorie need (including daily activity) and lift weights at the gym. To lose body fat while keeping muscle, I drop below that number, keep protein high, and keep lifting heavy.