Using Lean Body Mass To Calculate Protein Needs ("Zone Method")

Using Lean Body Mass and Activity Level

Some authors argue that the lean body mass (that is, the non-fat portion of the body) is the primary determinant of protein needs, and others argue that activity level should also be taken into account. Sears (the "Zone" diet) and Eades ("Protein Power") are examples of authors who take both of these factors into account in their protein recommendations.

What Is Lean Body Mass?

Lean body mass is the amount of body weight that is not fat.

Learn more about body fat percentage and lean body mass.

How Do I Find Out My Lean Body Mass?

Using this method to calculate body fat, find out what percentage of your body weight is fat. The rest of it is lean body mass. So if you weigh 150 lbs, and your body fat percentage is 30%, that is 45 lbs. That means your lean body mass is 150 minus 45, which is 105 lbs.

Now What?

According to the formula used by Sears, the pounds of lean body mass should be multiplied by the following, depending on activity level, to get the daily protein requirement in grams:

  • Sedentary - multiply lbs of lean body mass by .5
  • Light activity (e.g. walking) - multiply by .6
  • Moderate (30 minutes of vigorous activity 3 days per week) - .7
  • Active (1 hour per day 5 days per week) - .8
  • Very Active (10 hours of vigorous activity per week - .9
  • Athlete - multiply by 1.0

Some experts also suggest that obese people go to the next highest category - basically, it's like doing whatever you're already doing, only with extra weights.


Suppose we have a 160 lbs person who has 25% body fat. This person has 120 lbs of lean body mass. If the person is sedentary, they should consume 60 grams of protein per day. If moderately active, 84 grams, and so on. Note that ​a 180 lb person who has 30% body fat would also have 120 lbs of lean body mass, so the same figures would apply.

It turns out that for most people, these numbers come pretty close to the standard way of figuring out protein needs.

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