Is the Anabolic Window Real?
Protein Intake for Muscle Development
Protein is an essential nutrient for building muscle.
With a diet rich in nutrients, protein intakes up to 1.6-1.8 g/kg of body weight are optimal for muscle protein synthesis (MPS) in healthy individuals(1)(3).
Those 65 or older do better with protein at or under 1.6 g/kg of body weight. Meanwhile, greater intakes of 2.2 g/kg may be required for elite athletes or individuals with a caloric deficit (1)(2).
What is the Anabolic Window?
The concept is that consuming a protein-rich meal can induce more significant effects on MPS within a narrow 30-60-minute window after exercise.
This concept stems from the late 1990s to early 2000s, mainly from research on endurance athletes' ability to replenish glycogen (3).
Current Evidence
There is sufficient evidence to state that carbohydrates after endurance training are beneficial if consumed within a narrow window post-exercise (4).
However, the evidence seems inconsistent in resistance training due to varied protein intake in control groups and limited sample sizes (3).
A 2017 controlled trial examined the effects of pre-workout nutrient timing versus post-workout nutrient timing on 21 resistance-trained men for ten weeks (5). Rather than looking at MPS, the researchers analyzed body composition, BMI, strength, and measurements. This is important because MPS does not directly correlate to hypertrophy (muscle cell enlargement).
The pre-workout group was instructed not to eat anything up to 3 hours after their workout, and the post-workout group was instructed not to eat anything 3 hours before their workout. This allowed no interference with additional protein intake before or after each resistance training for each intervention group.
Both groups were given a supplement containing 25 grams of protein and 1 gram of carbohydrates, which they would consume before or after their workout, depending on their intervention group.
Similar effects were concluded in both intervention groups, suggesting that nutrient timing may be less important than total protein intake.
Key Takeaways
Resistance training is essential for hypertrophy and muscle growth. An adequate stimulus on a consistent regimen will allow for greater strength and lean body mass improvements (6).
The 2018 meta-analysis and the 2017 controlled trial demonstrated that total protein intake is more important than nutrient timing (3)(5).
To optimize the nutrient timing of pre- and post-exercise meals, you can consume 0.4-0.5 g/kg of protein with a 4-6 hour spacing between both meals (3). This will allow ample time for digested protein to be absorbed and utilized; however, timing also varies depending on meal size and nutrient density.
Studies also demonstrate that the “anabolic window” is not a narrow 30-60-minute window; it can last up to 24 hours after a resistance training interval (3). Therefore, stimulus and total protein intake are the most critical factors. Consume meals when they are convenient and sustainable to meet your hypertrophic goals.
