How Protein and Carbs Work Together to Build Muscle

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Hormones play a major role in muscle breakdown and their subsequent rebuilding. Different food groups serve to regulate these hormones, and proper timing of fuel intake can help you fine tune your hormone levels for successful muscle rebuilding.

Cortisol and Insulin

Two hormones that play a vital role in muscle production are cortisol and insulin. Cortisol is created during intense exercise.  Its major function is to generate fuel by breaking down muscle stores. Insulin works to reduce cortisol response, helping to decrease muscle breakdown.

Workout Fuel

Insulin also helps muscles rebuild, but without adequate carbohydrate consumption, muscle cells can become insulin resistant. And protein consumed without carbohydrates is less efficient. That's why you should consume carbohydrates and protein during a workout.

By consuming carbohydrates during exercise, you can increase insulin production and reduce cortisol's response. With less cortisol produced, you'll have less muscle breakdown. Protein allows for sustained energy and helps the body recover faster. Liquid meals, such as a protein smoothie with fruit, are beneficial during this important rebuilding stage because they are easily digested.

Between workouts, carbohydrates and protein work together to fully replenish muscle energy stores and build new muscle. To reap the most benefit, consume carbs and protein at each meal and snack.

The protein recommendation for a strength athlete is 0.9 to 1.2 grams per pound of bodyweight. Different types of protein—whey and casein—help build muscle. Whey is fast acting and best consumed during and immediately following a workout. Casein is more slowly digested. It's great to take before bed to help minimize muscle loss during the overnight fast. (Learn more about the differences between whey and casein protein.)

Here are daily recommendations for all food groups, listed as a percentage of total daily calories:

  • Protein — 21-24 percent
  • Carbohydrates — 43-46 percent
  • Fat — 33 percent

If you follow a 2,000-calorie diet, your daily recommendations would be 105-120 grams of protein/day, 215-230 grams of carbohydrate/day and 73 grams of fat/day. (Read "How Much Protein Do Athletes Need?" to figure out how much protein you should consume.)

You can easily meet these dietary requirements without supplements. For example, here is a sample day's worth of protein:

  • Breakfast: 2 eggs = 12 grams protein
  • Snack: 2 oz. almonds = 12 grams protein
  • Lunch: 6 oz. turkey = 30 grams protein
  • Snack: 8 oz. Greek yogurt = 16 grams protein
  • Dinner: 6 oz. salmon = 38 grams protein

This adds up to 108 grams of protein. With a little meal planning, you can easily meet your daily requirements.

Sources:  Nutrient Timing for Peak Performance, by John Ivy and Robert Portman; Sports Nutrition Guide Book, by Nancy Clark


Kait Fortunato earned her bachelor's degree in dietetics and completed her internship through the University of Maryland. She focuses on individualized nutritional recommendations for athletes of all ages and activity levels, and she is an active member of the Sports Dietetic Practice Group of the Academy of Nutrition and Dietetics. Visit for running and recipe updates.

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