The “Anabolic Window”: How Important is it for Muscle Gains?

Protein consumption can help suppress appetite, increase energy expenditure, increase muscle mass and decrease body fat1. When the body has sufficient protein stores available, muscle anabolism, where muscle mass is built or maintained, occurs. But without enough protein, muscle mass breakdown, called muscle catabolism, occurs. Our bodies fluctuate between these states depending on available resources.  

The Building Blocks of Muscle

So how can you gain muscle mass? During activities like weightlifting, stress and tension cause microtears in the muscle. The microtears activate a protein builder called mTOR, which uses available protein stores for muscle protein synthesis (MPS)2Muscle proteins are built from twenty different amino acids, nine of which are essential. Essential amino acids must be obtained from a balanced diet2. For example, branched chain amino acids (BCAA’s), specifically leucine, valine and isoleucine, are three essential amino acids that can be obtained from foods such as meat, eggs, fish, soy and rice2BCAA’s are a key component to MPS2.

So How Effective is Nutrient Timing?

During and after a workout, our bodies use energy from stored carbohydrates and fats. If these become too depleted, our bodies turn to protein for energy, which can be obtained from breaking down muscle. So, the idea of an “anabolic window3” was introduced. If protein and carbohydrate consumption occurred within 45 minutes after a workout, this would maximize nutrient uptake and metabolism within muscles, shift the body from a catabolic to anabolic state, and enhance recovery3. However, recent studies have found that the “anabolic window” is a common misconception3.  Surprisingly enough, chugging a protein shake immediately after a workout is not actually giving you that much of a recovery advantage. In fact, new research is showing that as long as minimal protein targets are hit during the day, this can maximize performance and induce similar muscle gains3

Hitting Those Daily Protein Levels

So how much protein should you be eating in a day? Around 15-30% of calories should be from protein sources1. For sedentary individuals, protein intake should sit around 0.8g/kg of body weight per day1. For training individuals, protein intake increases to 1.2-2.0 g/kg of body weight per day1. Take an individual that weighs 68 kg (approximately 150 lbs). For a more sedentary individual, this would mean consuming approximately 54 g of protein per day. For training individuals, up to 136 g of protein per day. For context, a chicken breast, an egg, and a tablespoon of peanut butter have approximately 30 grams of protein, 7 grams of protein, and 4 grams of protein respectively.

Let’s recap. Muscle anabolism, aka muscle gain, occurs when sufficient protein sources, specifically BCAA’s, are available in the body for mTOR to use. BCAA’s are essential amino acids, meaning that they need to be consumed from foods. For a long time, the “anabolic window” was believed to be a critical time period after a workout in which protein and carbohydrates needed to be consumed to maximize recovery and muscle gains. As it turns out, the “anabolic window” is much less time constrained. So no need to worry; if you forget your protein shake after hitting the gym, you won’t lose all your hard work for the day. Just make sure to hit your daily protein targets!

  1. Effects of dietary supplementation in sport and exercise: a review of evidence on milk proteins and amino acids –[][][][]
  2. Branched-chain Amino Acids: Catabolism in Skeletal Muscle and Implications for Muscle and Whole-body Metabolism –[][][][]
  3. Nutrient Timing: A Garage Door of Opportunity? –[][][][]

1 Comment

Great info Akaya. I will keep in mind the protein targets for the day rather than the anabolic window after a workout.