Protein is never a key exercise fuel, but it’s critical for other reasons. During most exercise, protein contributes less than 5 percent of the total energy, although it may rise to 10 to 15 percent during a prolonged event like a marathon or Ironman triathlon. Taking in enough dietary protein is important because dietary protein allows your muscles to be repaired after exercise and promotes the synthesis of hormones, enzymes, and other body tissues formed from amino acids, the building blocks of protein.
You should consume at least 12 to 35 percent of your daily calories as protein. For most people this means taking in at least 60 grams of protein daily.
About half of the 20 amino acids are considered essential in your diet, meaning that you must consume them or your body will suffer from protein malnutrition, which causes the breakdown of muscles and organs. Essential amino acids are found in meats, poultry, fish, dairy, eggs, and soy products; all plant-based foods besides soy are lacking one or more essential ones, but taking in combinations of plant sources (like rice and beans) can supply what you need.
Your body can make the rest of the amino acids itself (they are the nonessential ones). But you need to have enough protein in your diet overall to synthesize body proteins after workouts, which is a critical time for increases in strength, aerobic capacity, or muscle size.
Because protein is important to overall health but isn’t a major exercise fuel, you do need to worry about consuming enough, although it doesn’t have to happen right before or during an activity. You’ll get most effective restoration of liver glycogen if you keep your blood glucose levels in tight control after exercise. Consuming a small amount of protein along with carbohydrate (in a ratio of 1:4, or one gram of protein to every four grams of carbohydrate) after an activity may help you repair your muscles and get stronger more quickly.
Typically, an ounce of chicken, cheese, or meat has about 7 grams of protein.
Taking in more protein and slightly less carbohydrate after exercise can help keep your blood glucose more stable over time because protein takes three to four hours to be fully digested, and some protein is converted into blood glucose. You can eat protein strategically to prevent later-onset hypoglycemia, which insulin users are more likely to get. Have some in your bedtime snack (along with fat and carbohydrate) to prevent nighttime lows after a day of strenuous or prolonged activity, if you use insulin.
Taking in some protein along with carbohydrate right after hard or long workouts may help your body replenish its glycogen stores more effectively. Though anyone who is getting older—and that includes all of us—can benefit from taking in enough protein, supplements are usually not the optimal way to get enough. Let me explain why.
As you get older, your body may need more protein compared to when you were younger to form, maintain, and repair muscles and other body structures. Anyone who is doing regular exercise training also needs more protein to repair and build muscle, but you can usually get this amount (and more) when you’re eating a balanced meal plan with adequate calories. To figure out how much you need, find the category that fits your age and training, and multiply your body weight (in pounds or kilograms) by the grams found in the corresponding table column.
TABLE Recommended Protein Intake by Training Status and Age
Per Pound Body Weight Per Kilogram Body Weight
Adults 19 to 50 years (inactive) 0.36 grams 0.8 grams
Adults over 50 years (inactive) 0.5 grams 1.1 grams
Endurance training 0.55–0.64 grams 1.2–1.4 grams
Strength training 0.68–0.77 grams 1.5–1.7 grams
Calorie deprived (diets) 0.73–0.82 grams 1.6–1.8 grams
The biggest myth about amino acid supplements, and protein in general, is that you must load up on them to gain muscle. That’s just not true. The protein requirement for strength-training athletes may be about twice as high as normal, but most people in the United States already consume more than these higher amounts of protein in their daily diets.
To put it in perspective, to gain one pound of muscle mass a week (a realistic maximum), a strength-training athlete needs no more than 14 extra grams of quality protein per day. You can easily get this amount from these sources:
» About two 8-ounce glasses of milk
» 2 ounces of lean meat, chicken, fish, or cheese (which isn’t much)
» Slightly more than 2 eggs (only the whites contain protein)
Adequate intake of protein also helps to maintain lean body mass when you lose weight on a diet and can help you gain more muscle mass from exercise training.
Reference: Excerpted from Colberg, SR, “Chapter 7: Eating Right for Exercise,” Diabetes & Keeping Fit for Dummies, Wiley, 2019.
Sheri R. Colberg, PhD, is the author of The Athlete’s Guide to Diabetes: Expert Advice for 165 Sports and Activities (the newest edition of Diabetic Athlete’s Handbook). She is also the author of Diabetes & Keeping Fit for Dummies, co-published by Wiley and the ADA. A professor emerita of exercise science from Old Dominion University and an internationally recognized diabetes motion expert, she is the author of 12 books, 30 book chapters, and over 420 articles. She was honored with the 2016 American Diabetes Association Outstanding Educator in Diabetes Award. Contact her via her websites (SheriColberg.com and DiabetesMotion.com).