3 Ways to Calculate Your Daily Protein Needs

Estimating Intake Needs Based on Fitness Levels

Skin calipers

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Some health experts will argue that lean body mass (the non-fat portion of the body) is the primary determinant of your protein needs. Others contend that your level of physical activity should also factor into the equation.

The latter seems a fair argument given that someone with an active lifestyle would inherently burn more protein than someone who is relatively sedentary. Even if both have similar lean body masses, it doesn't make sense that both would have the same protein needs.

As a general guideline, the Office of Disease Prevention and Health Promotion (ODPHP) recommends a daily protein intake of no less than 0.36 grams of protein per pound if you are sedentary. If you have a physically demanding job or do intense workouts, you would need more. Just how much is the question many health experts continue to wrestle with.

To this end, a number of governmental and private authorities have established unique methods of calculating optimal protein intake. Here are three you should consider.

Recommended Dietary Allowance (RDA) Method

Recommended dietary allowance (RDA) is the term used to describe the daily intake of nutrients considered sufficient for 97 percent of the population. In terms of protein, the amount you need depends on your age, sex, current health, fitness level, and whether you need to gain or lose weight.

The RDA method takes into account your estimated daily calories needs as outlined in the "2010-2020 Dietary Guidelines" for Americans issued by the ODPHP. Estimates range from 1,600 to 2,400 calories per day for women and 2,000 to 3,000 calories per day for men. Within each age and sex category, the lower end of the range is for sedentary people; the higher end is for active ones.

Based on these recommendations, you can calculate how many of the calories should come from protein. Depending on your sex, age, and other factors, your range could be anywhere from 10 percent to 25 percent of your total daily calories.

While a doctor or dietitian would be best suited to determine your ideal percentage, there are some general guidelines that can help:

  • Children and teenagers need more protein (up to 25 percent of total calories) than adults.
  • Men need more protein than women.
  • Pregnant and lactating women need more protein than non-pregnant women.
  • Older adults need more protein than middle-aged adults.
  • People with liver or kidney disease need to decrease protein intake (to 10 percent of total calories or less).

Once you have determined how many of your calories should be derived from protein—by multiplying your total calories by 10 percent to 25 percent—you can calculate your actual intake in grams. Generally speaking, there are 4 calories per gram of protein, meaning that 40 calories derived from protein equal 10 grams of protein (40 ÷ 4 = 10).

How to Use the RDA Method

  1. To calculate your total calories needs, refer to the "2015-2020 Dietary Guidelines for Americans." For example, a sedentary male between 21 and 40 needs 2,400 calories per day.
  2. To calculate the percentage derived from protein, multiply your total calories by the estimated percentage of protein needed. For the same adult male, that might be 20 percent, or 480 calories (2,400 x 20% = 480)
  3. To translate calories to grams, divide the calories derived from protein by 4. For the same male adult, that would be 120 grams of protein daily (480 ÷ 4 = 120).

The Zone Diet Technique

The one shortcoming of the RDA method is that much of it is guesswork. Without input from your doctor or dietitian, you might very well be guessing whether 15 percent of your calories should come from protein or 30 percent.

To this end, a number of diet experts have constructed their own methodologies based on a person's fitness level. One of these is Barry Sears, author of the bestseller, "The Zone Diet." While Sears' methods are not endorsed by any public health authority, many fitness pros have embraced them as a means to create a more appropriate and individualized diet plan.

The Zone Diet formula is broken down into two parts: first, a calculation of your lean body mass (LDM), and, a second, the assignment of a percentage to your physical activity level.

Calculating Lean Body Mass

Lean body mass (LBM) is simply the amount of body weight that is not fat. It includes bone, water, muscle, organs, and other tissues. LBM is considered an important measure for metabolism since muscle burns more calories for energy than fat. Think of lean body mass as a simple mathematic equation: Body weight minus body fat equals lean body mass.

To begin the calculation, start by figuring how what percentage of your body is fat. This is called, the body fat percentage (BFP). There are a variety of ways to do this:

  • You can use a body fat scale that employs something called bioelectric impedance to estimate your body fat. It is a simple technology in which high-frequency waves are sent through tissue to determine to your total body water (TBW), the figure of which is used to calculate your BFP.
  • A simpler tool is called a skinfold caliper, which looks rather like plastic scissors. To use the device, simply pinch an area of skin (such as under the upper arm or on the back) and clamp on the calipers. The thicker the pinched skin, the more fat there is. While quick and easy use, the device is prone to user error.
  • You can get a far more accurate reading with a radiological technology known as a dual-energy X-ray absorptiometry (DEXA) scan. Clearly, the main impediments of use are cost, convenience, and radiation exposure.
  • Less invasive but almost as involving is a procedure known as hydrostatic weighing in which your body is placed underwater. The displacement of water is used to calculate your BFP. Of all the methods, this is considered the gold standard for measuring BFP.
  • The final method is called air displacement plethysmography in which air is used to make the displacement rather than water. It is costly technology and not widely available.

How to Calculate Your Lean Body Mass

  1. To calculate your total body fat, multiply your body weight by the BFP percentage. For example, if you weigh 150 pounds and your BFP is 30 percent, then 45 of those pounds would be fat (150 x 30% = 45).
  2. To calculate your lean body mass, simply subtract your body fat weight from your total body weight. Using the same example, the lean body mass would be 105 (150 - 45 = 105).

Calculating Daily Protein Need

According to the Zone Diet, your LBM only provides the baseline for analysis. To determine your daily protein need, you next need to multiply your LBM by the appropriate activity level as follows:

  • Sedentary (generally inactive): multiply by 0.5
  • Light activity (includes walking or gardening): multiply by 0.6
  • Moderate (30 minutes of moderate activity, thrice weekly): multiply by 0.7
  • Active (one hour of exercise, five times weekly): multiply by 0.8
  • Very active (10 to 20 hours of exercise weekly): multiply by 0.9
  • Athlete (over 20 hours of exercise weekly): multiply by 1.0

Examples of the Zone Diet Technique

Based on the Zone Diet formula, a 150-pound person with an LBM of 105 would require a daily protein intake of roughly:

  • 53 grams if sedentary (105 x 0.5 = 52.5)
  • 63 grams if lightly active (105 x 0.6 = 63)
  • 74 grams if moderately active (105 x .0.7 = 73.5)
  • 84 grams if active (105 x 0.9 = 84)
  • 95 grams if very active (105 x 0.9 = 94.5)
  • 120 grams if athletic (105 x 1.0 = 105)

The calculation can end up making a huge difference in how much or little protein you can eat each day. For example, a 4-ounce hamburger patty, a 4-ounce chicken breast, or seven slices of thick-cut bacon each offers around 30 grams of protein. Based on the Zone Diet rules, a person who is active would be able to eat an extra burger per day than someone who is sedentary, irrespective of the LBM.

The NAM Method

Although the Zone Diet formula is useful for designing a more tailored diet plan, it does have its limitations. For example, it does not take into account the impact that obesity and older age may have on daily protein needs.

As an alternative, the non-profit National Academy of Medicine (NAM) offers a more standardized scale of measurement, whereby your daily protein requirement is calculated simply by multiplying 0.37 by your total body weight.

Using the above-listed example, a man weighing 150 pounds would multiply 150 by 0.37 to get the daily protein requirement of 55 grams. While it is certainly the easiest methodology to use, there is no variation based on age or activity level. It remains the same whether you are a couch potato or a decathlete.

A Word From Verywell

In the end, there is no one single, surefire way to calculate your daily protein needs. While each of the prescribed methods points you in the right direction, they have their shortcomings and limitations.

To get a more insightful assessment, visit a qualified nutritionist or dietitian who can help you design a diet plan based on your individual needs and goals.

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