October 30, 2023 by Fuel & Fortify

Understanding the Anabolic Window and Optimal Protein Intake

None of us want to be shortchanged when it comes to stringing out every potential gain when we’ve gone through the hard toil of a gruelling workout. The strain we put on our muscles under extreme duress during these workouts leads to microtears, prompting them to repair and grow.

But muscle growth on the back o this morning is not solely dependent on the reps we’ve pumped out over the course of our workout. What we consume after exercising can significantly enhance or hinder our recovery. The concept of the “anabolic window,” also known as the protein window, has long been a subject of debate. This idea suggests a limited timeframe after a workout when consuming protein is believed to optimise muscle growth and repair.

On the surface, it seems reasonable to assume that we should be downing a protein shake after heaving lifting in the gym or an intense interval session on the track. Intense exercises deplete glycogen stores and amino acids, often making our bodies remind us of this depletion through hunger. Protein should not be isolated in these replenishment endeavours, but rather a combination of nutrients, fluids, and rest in order to recover optimally.

At a cellular level, the notion of a shortly followed “anabolic window” is believed to spike our muscle protein synthesis. While it is tempting to believe in the concept of a specific time frame after exercise when consuming protein can significantly enhance muscle growth and repair, current research suggests that this window might not be as rigid as once thought.

The Myth of the 30-Minute Rule

So how did we settle on the 30 to 60 minute “anabolic window”—well it’s complicated.

Early studies muddied the waters, yielding conflicting results and often emphasising the urgency of immediate consumption. A comprehensive meta-analysis, examining randomised controlled trials where one group consumed protein within an hour after exercise, while another delayed intake by at least two hours, highlighted a crucial point: the impact of protein timing on muscle hypertrophy (the process of muscle growth and enlargement) is relatively minor. Instead, the key factor in promoting exercise-induced muscle development lies in overall daily protein intake.

The protein shake and supplement industry however, continues to profit significantly from this entrenched belief. They have managed to instill a sense of urgency in people, convincing them that protein must be consumed immediately.

However, recent research challenges this notion. While post-workout nutrition remains important, focusing solely on this immediate window overlooks a broader perspective. Studies emphasise the significance of total protein intake throughout the day. Distributing protein intake evenly across meals rather than concentrating it in one particular post-workout meal has been shown to maintain a higher peak MPS (at 24 hours) by up to 25%. This shift in perspective encourages a more balanced and sustained approach to protein consumption, debunking the whole rigid 30-minute concept.

Combining Carbs and Protein

The practice of combining carbohydrates and protein in post-workout meals has been a topic of extensive discussion. The theory behind this approach is carbohydrate coingestion may enhance MPS by elevating insulin levels, inhibiting muscle protein breakdown, but doesn’t affect protein synthesis alone.However, various studies comparing a substantial protein intake (20–25g) with the simultaneous intake of carbohydrates—either a small (0.15 g·kg−1·h−1) or large (0.6 g·kg−1·h−1) amount—have shown that the additional carbohydrates do not significantly enhance muscle protein synthesis.

The choice however, depends on the session’s goal. Resistance and endurance exercise can deplete muscle glycogen by 30–40%—and carbohydrate intake aids in faster glycogen replenishment. This ingestion of carbohydrates is vital from an “optimisation” standpoint rather than “adaptation.” Optimisation focuses on swift recovery, while the latter aims to maintain the natural training stimulus, allowing the body and nervous system to return to homeostasis without expediting recovery.

The Role of Intermittent Fasting

Fasting is an exception to the rule in all of this. To build muscle, muscle protein synthesis (MPS) must be greater than protein breakdown (MPD). In a non-fasted state, post-workout protein breakdown only slightly increases. However, fasting leads to a significant rise in MPD, resulting in a negative protein balance. In this situation, opting for a protein shake post-workout is advisable source.

The True Time Horizon: An Extended Window

By definition, discussions about any specific time “window” should consider both before and after a workout.

In a study comparing nutrient timing before and after resistance training. Participants consumed whey protein either before or after training, with a 3-hour fasting period on the opposite side of protein intake. Muscle hypertrophy remained consistent over 10 weeks between the two groups. The research revealed that consuming protein before exercise counteracts the advantages of immediate post-workout nutrition, highlighting the crucial role of nutrient timing.

Many researchers have supported the idea from previous studies that “pre-supposition that training is carried out in a fasted state”. For those not fasting, a balanced meal with protein and carbs 3-4 hours before and after a workout is advisable. As this study suggests however, nutrient timing is highly complex, suggesting individual factors such as training status, age, and overall protein intake need consideration.

Recommended Dosage: Protein Intake per Kilogram of Body Weight

To optimise post-exercise intervention, research suggests that ingesting as little as 20g of protein, taken 4–6 hours after the previous meal, can maximally stimulate muscle protein synthesis (MPS) and muscle protein balance after resistance exercise (source). However, it’s crucial to adopt a broader perspective on protein intake, considering it within the context of daily consumption.

The current U.S. Recommended Dietary Allowance (RDA) for minimally active adults, aimed at preventing deficiency, is 0.8 grams of protein per kilogram of body weight (source). While even as low as 0.5g per kg can increase lean body mass, the sweet spot appears to be between 1.2 to 1.6 gram per kilogram.. For instance, an 80kg male (176.4 pounds) would need to consume between 96 and 128 grams of protein daily, coupled with resistance training (yes, if you have to put in the work still!), to support muscle growth.

Summary

Modern protein marketing employs clever tactics, convincing you that chugging a post-exercise shake is the key to realising your gains. Yet, the focus should widen and take into account your daily protein requirements, ensuring a balanced intake throughout the day.

One aspect we won’t delve into in this article (simply because the topic is so extensive!), is the best sources of protein. This topic is undeniably one of the most controversial in the #DietWars, and this post does not intend to dissect the discussions featured in documentaries like Game Changers. We’ll save that conversation for another post!

What we want to emphasise is that the directive “get more protein” shouldn’t be equated with “eat more meat.” Many people might be surprised to discover the plethora of plant-based protein options available. These options should unquestionably be included as part of a balanced diet.