By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital

Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

Protein is essential for building and repairing muscle, fostering growth and development, and assisting with basic movements like getting out of a chair. Figuring out your protein needs is not a one-size-fits-all process, though. Professor Anding explains how to calculate your needs based on weight, age, and activity level.

Calculating Protein Requirements

What are the protein requirements for your body? Keep in mind that the protein requirements listed in textbooks are based on a kilogram of body weight, not pounds. To get from pounds to kilos, divide by 2.2. 

Normal adult needs are less than a gram per kilo. In fact, most normal adult needs are 0.8 grams per kilogram of body weight. 

You may be wondering, though, if you should use your ideal body weight or your actual weight. If you’re within a normal weight range, you can use your actual body weight. 

If you are on a weight management plan, you probably need to use your ideal body weight because excess body fat doesn’t have the same demand for protein or amino acids as muscle does. Conversely, if you’re a very physically active person, you probably want to use your actual weight, even if you’re 20 or 30 pounds overweight based on the scale.

During periods of active growth and development, protein requirements are higher. Infants require two grams per kilogram of body weight.

Another period of rapid growth is during adolescence and puberty, and these individuals need one gram of protein per kilogram of body weight. Some schools of thought suggest that as we grow older, we don’t absorb protein as effectively, and thus the protein requirements for older Americans may be greater than the traditional adult requirements. According to Professor Anding, though, it is still too early to draw any definitive conclusions from the research.

Protein Needs for Athletes

Athletes have rapid development and are trying to increase their muscular mass. Endurance athletes are long-distance runners and bike riders. They need anywhere between 1.2 and 1.4 grams of protein per kilo. 

Strength athletes, according to Professor Anding, are people who lift weights in a serious fashion. This category includes football, basketball, and tennis players at the high school and college levels.

The requirements for these athletes are 1.6 to 1.8 grams of protein per kilogram of body weight. Is it true that an athlete needs more protein? 

“The answer is yes, but I’m going to tell you, in my experience with my Rice football players, I used to track how many grams of protein they were getting,” Professor Anding said. “They were consuming up to four grams of protein per kilogram of body weight…that’s a colossal waste of money.”

Additionally, such excessive protein intake can increase your urinary acid load, which may increase the likelihood of kidney stones. Keep in mind that excess protein doesn’t translate into increased function and can contribute to obesity. 

If you exceed your protein requirements, that becomes a caloric excess. Even professional football players can become overweight from eating too much protein, as excess calories are always going to be converted into body fat. Most sources of complete protein also contain animal fat, and therein lies the issue. 

For muscle injury and repair, the protein requirements are 1.5 to two grams of protein per kilogram. For significant injuries such as burns, protein requirements can exceed two grams per kilogram.

Protein Deficiency Diseases

Some people experience protein deficiency diseases such as marasmus, which can result from anorexia nervosa. Someone may be eating what appears to be a healthy diet of fruits, vegetables, and tofu, but the calories and the protein are inadequate. 

Hypoalbuminemia malnutrition is another protein deficiency disease. “Hypo” means low, “albumin” is blood protein, and “emic” means in the blood. Low albumin can be caused by a stress response, meaning a serious injury such as a burn or gunshot wound. 

During times of physical stress, the body chews up protein. Even though we have lots of calories stored as body fat, during times of physical stress, unfortunately the body draws from protein.

“I’ll give you a tragic example that I encountered early in my career,” Professor Anding said. “We had a woman come into the hospital that I was working at, and she was having a bunion repaired—truly minor surgery.”

The woman was about 5 foot 4 inches and somewhere in the range of 300 pounds. No one asked her if she had lost weight in the past six months, but it turned out that she’d lost about 100 pounds involuntarily because she had pneumonia. 

The pneumonia caused a physical stress, and even though she was overweight, she had lost a significant amount of body protein, developing hypoalbuminemic malnutrition. Her hospital stay was prolonged, and she ended up getting infected.

A defect in amino acid metabolism can alter protein function and sequence, and protein synthesis can stop. Additionally, some genetic disorders such as sickle cell disease can alter protein metabolism. 

In sickle cell disease, valine, an amino acid, is substituted on that chain for glutamic acid, and instead of the red blood cell being circular, it sickles or looks like a crescent moon. Symptoms include fatigue, dizziness, and joint pain.

Phenylketonuria is the inability to convert phenylalanine, an essential amino acid found in products such as NutraSweet^®, to tyrosine. Phenylalanine can build up in the blood and cause brain damage.

Therefore, if you have a protein deficiency disease, your protein requirements may be even higher. In situations such as these, it is best to consult with a doctor or nutritionist. 

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.