Guidelines on protein intake are often given based on a person's total body weight. A more accurate way to gauge the amount of protein you need, however, might be to base it on your lean mass weight. Lean body mass is everything in your body except fat, including muscle, skin, bones, blood and organs. Along with this, you also need to consider your activity levels and goals when setting protein targets.
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Going by total body weight, your optimal protein intake depends on a number of factors. In "Sports Nutrition for Coaches," sports dietitian Leslie Bonci writes that recreational athletes need between 0.5 and 0.75 gram of protein per pound of body weight each day, while athletes aiming to build muscle need 0.7 to 0.9 gram per pound each day. Teenage athletes, who are still in growth and development stages, may need up to 1 gram per pound of body weight.
The Pitfalls in Body Weight Guidelines
For the average person, protein intake guidelines based on total body weight are suitable, but for certain sectors of the population, they're not as reliable. Those who are very lean and carrying a higher amount of muscle mass may need more protein to maintain this muscle. Additionally, obese or severely overweight people would end up eating a very high amount of protein were they to base their protein consumption levels on total body weight as opposed to lean mass.
A 2011 article published in the "Journal of Sports Sciences" found that the leaner an athlete was, the more protein she required to prevent muscle loss. A 2013 review article from the "Journal of Sports Nutrition and Exercise Metabolism" also concluded that protein requirements to maintain muscle mass increased for athletes who became leaner through dieting. This literature review suggests that while restricting calories, lean athletes required 2.3 to 3.1 grams of protein per kilogram of lean body mass, which equates to 1.05 to 1.41 grams per pound of fat-free mass.
Working Out the Numbers
To determine how much protein you need based on lean mass, you first need to work out your lean body weight, or fat-free mass. The formula involves subtracting your body fat weight from your total body weight. To find your body fat, either have a trained professional measure you with skin fold callipers, or use a handheld body fat measurement machine. This will give you a body fat percentage reading, and from there you can work out your levels of lean weight. If you weigh 180 pounds, for instance, and your body fat is 20 percent, you have 36 pounds of fat. Subtract this from 180, and your lean weight is 144 pounds.